Set version to 1.0.3

* Implement a probing ETL source and do not require SSL certs for SslETLSource (#251)

Fixes #251

.dockerignore

@@ -0,0 +1 @@
+build/

.git-blame-ignore-revs

@@ -6,3 +6,4 @@
 
 # clang-format
 e41150248a97e4bdc1cf21b54650c4bb7c63928e
+2e542e7b0d94451a933c88778461cc8d3d7e6417

.github/actions/lint/action.yml

@@ -0,0 +1,13 @@
+runs:
+  using: composite
+  steps:
+    # Github's ubuntu-20.04 image already has clang-format-11 installed
+    - run: |
+        find src unittests -type f \( -name '*.cpp' -o -name '*.h' -o -name '*.ipp' \) -print0 | xargs -0 clang-format-11 -i
+      shell: bash
+
+    - name: Check for differences
+      id: assert
+      shell: bash
+      run: |
+        git diff --color --exit-code | tee "clang-format.patch"

.github/actions/sign/action.yml

@@ -0,0 +1,21 @@
+name: 'Sign packages'
+runs:
+  using: "composite"
+
+  steps:
+    - name: Sign
+      shell: bash
+      run: |
+        set -ex -o pipefail
+        echo "$GPG_KEY_B64"| base64 -d | gpg --batch --no-tty --allow-secret-key-import --import -
+        unset GPG_KEY_B64
+        export GPG_PASSPHRASE=$(echo $GPG_KEY_PASS_B64 | base64 -di)
+        unset GPG_KEY_PASS_B64
+        export GPG_KEYID=$(gpg --with-colon --list-secret-keys | head -n1 | cut -d : -f 5)
+        for PKG in $(ls *.deb); do
+          dpkg-sig \
+            -g "--no-tty --digest-algo 'sha512' --passphrase '${GPG_PASSPHRASE}' --pinentry-mode=loopback" \
+                  -k "${GPG_KEYID}" \
+                  --sign builder \
+                  $PKG
+        done

.github/actions/test/Dockerfile

@@ -0,0 +1,6 @@
+FROM cassandra:4.0.4
+
+RUN apt-get update && apt-get install -y postgresql
+COPY entrypoint.sh /entrypoint.sh
+
+ENTRYPOINT ["/entrypoint.sh"]

.github/actions/test/entrypoint.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+
+pg_ctlcluster 12 main start
+su postgres -c"psql -c\"alter user postgres with password 'postgres'\""
+su cassandra -c "/opt/cassandra/bin/cassandra -R"
+sleep 90
+chmod +x ./clio_tests
+./clio_tests

.github/workflows/build.yml

@@ -1,9 +1,9 @@
 name: Build Clio
 on:
   push:
-    branches:  [master, develop, develop-next]
+    branches:  [master, release, develop, develop-next]
   pull_request:
-    branches:  [master, develop, develop-next]
+    branches:  [master, release, develop, develop-next]
   workflow_dispatch:
 
 jobs:
@@ -11,40 +11,132 @@ jobs:
     name: Lint
     runs-on: ubuntu-20.04
     steps:
-      - name: Get source
-        uses: actions/checkout@v3
-
+      - uses: actions/checkout@v3
       - name: Run clang-format
-        uses: XRPLF/clio-gha/lint@main
+        uses: ./.github/actions/lint
 
   build_clio:
-    name: Build
+    name: Build Clio
     runs-on: [self-hosted, Linux]
     needs: lint
+    strategy:
+      fail-fast: false
+      matrix:
+        type:
+          - suffix: deb
+            image: rippleci/clio-dpkg-builder:2022-09-17
+            script: dpkg
+          - suffix: rpm
+            image: rippleci/clio-rpm-builder:2022-09-17
+            script: rpm
+    container:
+      image: ${{ matrix.type.image }}
+
     steps:
-      - name: Get Clio repo
-        uses: actions/checkout@v3
+      - uses: actions/checkout@v3
         with:
-          path: clio_src
-          ref: 'develop-next'
+          path: clio
 
-      - name: Get Clio CI repo
+      - name: Clone Clio packaging repo
         uses: actions/checkout@v3
         with:
-          path: clio_ci
-          repository: 'XRPLF/clio-ci'
-
-      - name: Get GitHub actions repo
-        uses: actions/checkout@v3
-        with:
-          repository: XRPLF/clio-gha
-          path: gha # must be the same as defined in XRPLF/clio-gha
+          path: clio-packages
+          repository: XRPLF/clio-packages
 
       - name: Build
-        uses: XRPLF/clio-gha/build@main
+        shell: bash
+        run: |
+          export CLIO_ROOT=$(realpath clio)
+          if [ ${{ matrix.type.suffix }} == "rpm" ]; then
+            source /opt/rh/devtoolset-11/enable
+          fi
+          cmake -S clio-packages -B clio-packages/build -DCLIO_ROOT=$CLIO_ROOT
+          cmake --build clio-packages/build --parallel $(nproc)
+          cp ./clio-packages/build/clio-prefix/src/clio-build/clio_tests .
+          mv ./clio-packages/build/*.${{ matrix.type.suffix }} .
 
-      # - name: Artifact clio_tests
-      #   uses: actions/upload-artifact@v2
-      #   with:
-      #     name: clio_output
-      #     path: clio_src/build/clio_tests
+      - name: Artifact packages
+        uses: actions/upload-artifact@v3
+        with:
+          name: clio_${{ matrix.type.suffix }}_packages
+          path: ${{ github.workspace }}/*.${{ matrix.type.suffix }}
+
+      - name: Artifact clio_tests
+        uses: actions/upload-artifact@v3
+        with:
+          name: clio_tests-${{ matrix.type.suffix }}
+          path: ${{ github.workspace }}/clio_tests
+
+  sign:
+    name: Sign packages
+    needs: build_clio
+    runs-on: ubuntu-20.04
+    if: github.ref == 'refs/heads/master' || github.ref == 'refs/heads/release' || github.ref == 'refs/heads/develop'
+    env:
+      GPG_KEY_B64: ${{ secrets.GPG_KEY_B64 }}
+      GPG_KEY_PASS_B64: ${{ secrets.GPG_KEY_PASS_B64 }}
+    strategy:
+      fail-fast: false
+      matrix:
+        type:
+          - suffix: deb
+            image: ubuntu:20.04
+            script: dpkg
+          # - suffix: rpm
+          #   image: centos:7
+          #   script: rpm
+    container:
+      image: ${{ matrix.type.image }}
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install dpkg-sig
+        run: |
+          apt-get update && apt-get install -y dpkg-sig gnupg
+      - name: Get package artifact
+        uses: actions/download-artifact@v3
+        with:
+          name: clio_${{ matrix.type.suffix }}_packages
+
+      - name: find packages
+        run: find . -name "*.${{ matrix.type.suffix }}"
+
+      - name: Sign packages
+        uses: ./.github/actions/sign
+
+
+      - name: Verify the signature
+        run: |
+          set -e
+          for PKG in $(ls *.deb); do
+            gpg --verify "${PKG}"
+          done
+
+      - name: Get short SHA
+        id: shortsha
+        run: echo "::set-output name=sha8::$(echo ${GITHUB_SHA} | cut -c1-8)"
+
+      - name: Artifact signed packages
+        uses: actions/upload-artifact@v2
+        with:
+          name: signed-clio-deb-packages-${{ steps.shortsha.outputs.sha8 }}
+          path: ${{ github.workspace }}/*.deb
+
+  test_clio:
+    name: Test Clio
+    runs-on: [self-hosted, Linux]
+    needs: build_clio
+    strategy:
+      fail-fast: false
+      matrix:
+        suffix: [rpm, deb]
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Get clio_tests artifact
+        uses: actions/download-artifact@v3
+        with:
+          name: clio_tests-${{ matrix.suffix }}
+
+      - name: Run tests
+        timeout-minutes: 10
+        uses: ./.github/actions/test

.gitignore

@@ -1,2 +1,4 @@
+*clio*.log
 build/
+.vscode
 .python-version

CMake/ClioVersion.cmake

@@ -0,0 +1,15 @@
+#[===================================================================[
+   read version from source
+#]===================================================================]
+
+file (STRINGS src/main/impl/Build.cpp BUILD_INFO)
+foreach (line_ ${BUILD_INFO})
+  if (line_ MATCHES "versionString[ ]*=[ ]*\"(.+)\"")
+    set (clio_version ${CMAKE_MATCH_1})
+  endif ()
+endforeach ()
+if (clio_version)
+  message (STATUS "clio version: ${clio_version}")
+else ()
+  message (FATAL_ERROR "unable to determine clio version")
+endif ()

CMake/deps/Remove-bitset-operator.patch

@@ -0,0 +1,24 @@
+From 5cd9d09d960fa489a0c4379880cd7615b1c16e55 Mon Sep 17 00:00:00 2001
+From: CJ Cobb <ccobb@ripple.com>
+Date: Wed, 10 Aug 2022 12:30:01 -0400
+Subject: [PATCH] Remove bitset operator !=
+
+---
+ src/ripple/protocol/Feature.h | 1 -
+ 1 file changed, 1 deletion(-)
+
+diff --git a/src/ripple/protocol/Feature.h b/src/ripple/protocol/Feature.h
+index b3ecb099b..6424be411 100644
+--- a/src/ripple/protocol/Feature.h
++++ b/src/ripple/protocol/Feature.h
+@@ -126,7 +126,6 @@ class FeatureBitset : private std::bitset<detail::numFeatures>
+ public:
+     using base::bitset;
+     using base::operator==;
+-    using base::operator!=;
+ 
+     using base::all;
+     using base::any;
+-- 
+2.32.0
+

CMake/deps/cassandra.cmake

@@ -10,7 +10,7 @@ if(NOT cassandra)
         ExternalProject_Add(zlib_src
             PREFIX ${nih_cache_path}
             GIT_REPOSITORY https://github.com/madler/zlib.git
-            GIT_TAG master
+            GIT_TAG v1.2.12
             INSTALL_COMMAND ""
             BUILD_BYPRODUCTS <BINARY_DIR>/${CMAKE_STATIC_LIBRARY_PREFIX}z.a
             )
@@ -33,7 +33,7 @@ if(NOT cassandra)
         ExternalProject_Add(krb5_src
             PREFIX ${nih_cache_path}
             GIT_REPOSITORY https://github.com/krb5/krb5.git
-            GIT_TAG master
+            GIT_TAG krb5-1.20
             UPDATE_COMMAND ""
             CONFIGURE_COMMAND autoreconf src && CFLAGS=-fcommon ./src/configure --enable-static --disable-shared
             BUILD_IN_SOURCE 1
@@ -66,7 +66,7 @@ if(NOT cassandra)
         ExternalProject_Add(libuv_src
             PREFIX ${nih_cache_path}
             GIT_REPOSITORY https://github.com/libuv/libuv.git
-            GIT_TAG v1.x
+            GIT_TAG v1.44.1
             INSTALL_COMMAND ""
             BUILD_BYPRODUCTS <BINARY_DIR>/${CMAKE_STATIC_LIBRARY_PREFIX}uv_a.a
             )
@@ -89,7 +89,7 @@ if(NOT cassandra)
     ExternalProject_Add(cassandra_src
         PREFIX ${nih_cache_path}
         GIT_REPOSITORY https://github.com/datastax/cpp-driver.git
-        GIT_TAG master
+        GIT_TAG 2.16.2
         CMAKE_ARGS
         -DLIBUV_ROOT_DIR=${BINARY_DIR}
         -DLIBUV_INCLUDE_DIR=${SOURCE_DIR}/include

CMake/deps/rippled.cmake

@@ -1,11 +1,13 @@
 set(RIPPLED_REPO "https://github.com/ripple/rippled.git")
-set(RIPPLED_BRANCH "1.9.0")
+set(RIPPLED_BRANCH "1.9.2")
 set(NIH_CACHE_ROOT "${CMAKE_CURRENT_BINARY_DIR}" CACHE INTERNAL "")
+set(patch_command ! grep operator!= src/ripple/protocol/Feature.h || git apply < ${CMAKE_CURRENT_SOURCE_DIR}/CMake/deps/Remove-bitset-operator.patch)
 message(STATUS "Cloning ${RIPPLED_REPO} branch ${RIPPLED_BRANCH}")
 FetchContent_Declare(rippled
   GIT_REPOSITORY "${RIPPLED_REPO}"
   GIT_TAG "${RIPPLED_BRANCH}"
   GIT_SHALLOW ON
+  PATCH_COMMAND "${patch_command}"
 )
 
 FetchContent_GetProperties(rippled)

CMake/install/install.cmake

@@ -3,8 +3,14 @@ set(CMAKE_INSTALL_PREFIX ${CLIO_INSTALL_DIR})
 
 install(TARGETS clio_server DESTINATION bin)
 # install(TARGETS clio_tests DESTINATION bin) # NOTE: Do we want to install the tests?
-install(FILES example-config.json DESTINATION etc RENAME config.json)
+
+#install(FILES example-config.json DESTINATION etc RENAME config.json)
+file(READ example-config.json config)
+string(REGEX REPLACE "./clio_log" "/var/log/clio/" config "${config}")
+file(WRITE ${CMAKE_BINARY_DIR}/install-config.json "${config}")
+install(FILES ${CMAKE_BINARY_DIR}/install-config.json DESTINATION etc RENAME config.json)
 
 configure_file("${CMAKE_SOURCE_DIR}/CMake/install/clio.service.in" "${CMAKE_BINARY_DIR}/clio.service")
 
-install(FILES "${CMAKE_BINARY_DIR}/clio.service" DESTINATION /lib/systemd/system)
+install(FILES "${CMAKE_BINARY_DIR}/clio.service" DESTINATION /lib/systemd/system)
+

CMake/version-config.h

@@ -1 +0,0 @@
-#define VERSION "@PROJECT_VERSION@"

CMakeLists.txt

@@ -1,6 +1,10 @@
 cmake_minimum_required(VERSION 3.16.3)
 
-project(clio VERSION 0.2.0)
+project(clio)
+
+if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 11)
+  message(FATAL_ERROR "GCC 11+ required for building clio")
+endif()
 
 option(BUILD_TESTS "Build tests" TRUE)
 
@@ -10,6 +14,22 @@ if(VERBOSE)
   set(FETCHCONTENT_QUIET FALSE CACHE STRING "Verbose FetchContent()")
 endif()
 
+if(NOT GIT_COMMIT_HASH)
+  if(VERBOSE)
+    message("GIT_COMMIT_HASH not provided...looking for git")
+  endif()
+  find_package(Git)
+  if(Git_FOUND)
+      execute_process(COMMAND ${GIT_EXECUTABLE} describe --always --abbrev=8
+          OUTPUT_STRIP_TRAILING_WHITESPACE OUTPUT_VARIABLE gch)
+      if(gch)
+          set(GIT_COMMIT_HASH "${gch}")
+          message(STATUS "Git commit: ${GIT_COMMIT_HASH}")
+          add_definitions(-DCLIO_GIT_COMMIT_HASH="${GIT_COMMIT_HASH}")
+      endif()
+  endif()
+endif() #git
+
 add_library(clio)
 target_compile_features(clio PUBLIC cxx_std_20)
 target_include_directories(clio PUBLIC src)
@@ -17,23 +37,25 @@ target_include_directories(clio PUBLIC src)
 include(FetchContent)
 include(ExternalProject)
 include(CMake/settings.cmake)
+include(CMake/ClioVersion.cmake)
 include(CMake/deps/rippled.cmake)
 include(CMake/deps/Boost.cmake)
 include(CMake/deps/cassandra.cmake)
 include(CMake/deps/Postgres.cmake)
 
-# configure_file(CMake/version-config.h include/version.h) # NOTE: Not used, but an idea how to handle versioning.
-
 target_sources(clio PRIVATE
+  ## Main
+  src/main/impl/Build.cpp
   ## Backend
   src/backend/BackendInterface.cpp
   src/backend/CassandraBackend.cpp
-  src/backend/LayeredCache.cpp
   src/backend/Pg.cpp
   src/backend/PostgresBackend.cpp
   src/backend/SimpleCache.cpp
   ## ETL
   src/etl/ETLSource.cpp
+  src/etl/ProbingETLSource.cpp
+  src/etl/NFTHelpers.cpp
   src/etl/ReportingETL.cpp
   ## Subscriptions
   src/subscriptions/SubscriptionManager.cpp
@@ -41,6 +63,7 @@ target_sources(clio PRIVATE
   src/rpc/RPC.cpp
   src/rpc/RPCHelpers.cpp
   src/rpc/Counters.cpp
+  src/rpc/WorkQueue.cpp
   ## RPC Methods
   # Account
   src/rpc/handlers/AccountChannels.cpp
@@ -51,6 +74,8 @@ target_sources(clio PRIVATE
   src/rpc/handlers/AccountObjects.cpp
   src/rpc/handlers/GatewayBalances.cpp
   src/rpc/handlers/NoRippleCheck.cpp
+  # NFT
+  src/rpc/handlers/NFTInfo.cpp
   # Ledger
   src/rpc/handlers/Ledger.cpp
   src/rpc/handlers/LedgerData.cpp
@@ -61,7 +86,10 @@ target_sources(clio PRIVATE
   src/rpc/handlers/TransactionEntry.cpp
   src/rpc/handlers/AccountTx.cpp
   # Dex
+  src/rpc/handlers/BookChanges.cpp
   src/rpc/handlers/BookOffers.cpp
+  # NFT
+  src/rpc/handlers/NFTOffers.cpp
   # Payment Channel
   src/rpc/handlers/ChannelAuthorize.cpp
   src/rpc/handlers/ChannelVerify.cpp
@@ -72,7 +100,7 @@ target_sources(clio PRIVATE
   # Utility
   src/rpc/handlers/Random.cpp)
 
-add_executable(clio_server src/main.cpp)
+add_executable(clio_server src/main/main.cpp)
 target_link_libraries(clio_server PUBLIC clio)
 
 if(BUILD_TESTS)

CONTRIBUTING.md

@@ -0,0 +1,123 @@
+# Contributing
+Thank you for your interest in contributing to the `clio` project 🙏
+
+To contribute, please:
+1. Fork the repository under your own user.
+2. Create a new branch on which to write your changes.
+3. Write and test your code.
+4. Ensure that your code compiles with the provided build engine and update the provided build engine as part of your PR where needed and where appropriate.
+5. Where applicable, write test cases for your code and include those in `unittests`.
+6. Ensure your code passes automated checks (e.g. clang-format)
+7. Squash your commits (i.e. rebase) into as few commits as is reasonable to describe your changes at a high level (typically a single commit for a small change.). See below for more details.
+8. Open a PR to the main repository onto the _develop_ branch, and follow the provided template.
+
+> **Note:** Please make sure you read the [Style guide](#style-guide).
+
+## Git commands
+This sections offers a detailed look at the git commands you will need to use to get your PR submitted. 
+Please note that there are more than one way to do this and these commands are only  provided for your convenience.
+At this point it's assumed that you have already finished working on your feature/bug.
+
+> **Important:** Before you issue any of the commands below, please hit the `Sync fork` button and make sure your fork's `develop` branch is up to date with the main `clio` repository.
+
+``` bash
+# Create a backup of your branch
+git branch <your feature branch>_bk
+
+# Rebase and squash commits into one
+git checkout develop
+git pull origin develop
+git checkout <your feature branch>
+git rebase -i develop
+```
+For each commit in the list other than the first one please select `s` to squash.
+After this is done you will have the opportunity to write a message for the squashed commit.
+
+> **Hint:** Please use **imperative mood** commit message capitalizing the first word of the subject.
+
+``` bash
+# You should now have a single commit on top of a commit in `develop`
+git log
+```
+> **Todo:** In case there are merge conflicts, please resolve them now
+
+``` bash
+# Use the same commit message as you did above
+git commit -m 'Your message'
+git rebase --continue
+```
+
+> **Important:** If you have no GPG keys setup please follow [this tutorial](https://docs.github.com/en/authentication/managing-commit-signature-verification/adding-a-gpg-key-to-your-github-account)
+
+``` bash
+# Sign the commit with your GPG key and finally push your changes to the repo
+git commit --amend -S
+git push --force
+```
+
+## Fixing issues found during code review
+While your code is in review it's possible that some changes will be requested by the reviewer.
+This section describes the process of adding your fixes.
+
+We assume that you already made the required changes on your feature branch.
+
+``` bash
+# Add the changed code
+git add <paths to add>
+
+# Add a folded commit message (so you can squash them later)
+# while also signing it with your GPG key
+git commit -S -m "[FOLD] Your commit message"
+
+# And finally push your changes
+git push
+```
+## After code review
+Last but not least, when your PR is approved you still have to `Squash and merge` your code. 
+Luckily there is a button for that towards the bottom of the PR's page on github.
+
+> **Important:** Please leave the automatically generated link to PR in the subject line **and** in the description field please add `"Fixes #ISSUE_ID"` (replacing `ISSUE_ID` with yours).
+> **Note:** See [issues](https://github.com/XRPLF/clio/issues) to find the `ISSUE_ID` for the feature/bug you were working on.
+
+# Style guide
+This is a non-exhaustive list of recommended style guidelines. These are not always strictly enforced and serve as a way to keep the codebase coherent rather than a set of _thou shalt not_ commandments.
+
+## Formatting
+All code must conform to `clang-format` version 10, unless the result would be unreasonably difficult to read or maintain.
+To change your code to conform use `clang-format -i <your changed files>`.
+
+## Avoid
+* Proliferation of nearly identical code.
+* Proliferation of new files and classes unless it improves readability or/and compilation time.
+* Unmanaged memory allocation and raw pointers.
+* Macros (unless they add significant value.)
+* Lambda patterns (unless these add significant value.)
+* CPU or architecture-specific code unless there is a good reason to include it, and where it is used guard it with macros and provide explanatory comments.
+* Importing new libraries unless there is a very good reason to do so.
+
+## Seek to
+* Extend functionality of existing code rather than creating new code.
+* Prefer readability over terseness where important logic is concerned.
+* Inline functions that are not used or are not likely to be used elsewhere in the codebase.
+* Use clear and self-explanatory names for functions, variables, structs and classes.
+* Use TitleCase for classes, structs and filenames, camelCase for function and variable names, lower case for namespaces and folders.
+* Provide as many comments as you feel that a competent programmer would need to understand what your code does.
+
+# Maintainers
+Maintainers are ecosystem participants with elevated access to the repository. They are able to push new code, make decisions on when a release should be made, etc.
+
+## Code Review
+PRs must be reviewed by at least one of the maintainers.
+
+## Adding and Removing
+New maintainers can be proposed by two existing maintainers, subject to a vote by a quorum of the existing maintainers. A minimum of 50% support and a 50% participation is required. In the event of a tie vote, the addition of the new maintainer will be rejected.
+
+Existing maintainers can resign, or be subject to a vote for removal at the behest of two existing maintainers. A minimum of 60% agreement and 50% participation are required. The XRP Ledger Foundation will have the ability, for cause, to remove an existing maintainer without a vote.
+
+## Existing Maintainers
+
+* [cjcobb23](https://github.com/cjcobb23) (Ripple)
+* [natenichols](https://github.com/natenichols) (Ripple)
+* [legleux](https://github.com/legleux) (Ripple)
+* [undertome](https://github.com/undertome) (Ripple)
+* [godexsoft](https://github.com/godexsoft) (Ripple)

README.md

@@ -1,9 +1,6 @@
-**Status:** This software is in beta mode. We encourage anyone to try it out and
-report any issues they discover. Version 1.0 coming soon.
-
 # Clio
-Clio is an XRP Ledger API server. Clio is optimized for RPC calls, over websocket or JSON-RPC. Validated
-historical ledger and transaction data is stored in a more space efficient format,
+Clio is an XRP Ledger API server. Clio is optimized for RPC calls, over WebSocket or JSON-RPC. Validated
+historical ledger and transaction data are stored in a more space-efficient format,
 using up to 4 times less space than rippled. Clio can be configured to store data in Apache Cassandra or ScyllaDB,
 allowing for scalable read throughput. Multiple Clio nodes can share
 access to the same dataset, allowing for a highly available cluster of Clio nodes,
@@ -12,9 +9,9 @@ without the need for redundant data storage or computation.
 Clio offers the full rippled API, with the caveat that Clio by default only returns validated data.
 This means that `ledger_index` defaults to `validated` instead of `current` for all requests.
 Other non-validated data is also not returned, such as information about queued transactions.
-For requests that require access to the p2p network, such as `fee` or `submit`, Clio automatically forwards the request to a rippled node, and propagates the response back to the client. To access non-validated data for *any* request, simply add `ledger_index: "current"` to the request, and Clio will forward the request to rippled.
+For requests that require access to the p2p network, such as `fee` or `submit`, Clio automatically forwards the request to a rippled node and propagates the response back to the client. To access non-validated data for *any* request, simply add `ledger_index: "current"` to the request, and Clio will forward the request to rippled.
 
-Clio does not connect to the peer to peer network. Instead, Clio extracts data from a specified rippled node. Running Clio requires access to a rippled node
+Clio does not connect to the peer-to-peer network. Instead, Clio extracts data from a group of specified rippled nodes. Running Clio requires access to at least one rippled node
 from which data can be extracted. The rippled node does not need to be running on the same machine as Clio.
 
 
@@ -25,11 +22,11 @@ from which data can be extracted. The rippled node does not need to be running o
 
 ## Building
 
-Clio is built with cmake. Clio requires c++20, and boost 1.75.0 or later.
+Clio is built with CMake. Clio requires at least GCC-11 (C++20), and Boost 1.75.0 or later.
 
-Use these instructions to build a Clio executable from source. These instructions were tested on Ubuntu 20.04 LTS.
+Use these instructions to build a Clio executable from the source. These instructions were tested on Ubuntu 20.04 LTS.
 
-```
+```sh
 # Install dependencies
   sudo apt-get -y install git pkg-config protobuf-compiler libprotobuf-dev libssl-dev wget build-essential bison flex autoconf cmake
 
@@ -49,28 +46,30 @@ Use these instructions to build a Clio executable from source. These instruction
 ```
 
 ## Running
-`./clio_server config.json`
+```sh
+./clio_server config.json
+```
 
 Clio needs access to a rippled server. The config files of rippled and Clio need
 to match in a certain sense.
 Clio needs to know:
-- the ip of rippled
-- the port on which rippled is accepting unencrypted websocket connections
+- the IP of rippled
+- the port on which rippled is accepting unencrypted WebSocket connections
 - the port on which rippled is handling gRPC requests
 
 rippled needs to open:
 - a port to accept unencrypted websocket connections
-- a port to handle gRPC requests, with the ip(s) of Clio specified in the `secure_gateway` entry
+- a port to handle gRPC requests, with the IP(s) of Clio specified in the `secure_gateway` entry
 
-The example configs of rippled and Clio are setup such that minimal changes are
+The example configs of rippled and Clio are setups such that minimal changes are
 required. When running locally, the only change needed is to uncomment the `port_grpc`
 section of the rippled config. When running Clio and rippled on separate machines,
 in addition to uncommenting the `port_grpc` section, a few other steps must be taken:
-1. change the `ip` of the first entry of `etl_sources` to the ip where your rippled
+1. change the `ip` of the first entry of `etl_sources` to the IP where your rippled
 server is running
-2. open a public, unencrypted websocket port on your rippled server
-3. change the ip specified in `secure_gateway` of `port_grpc` section of the rippled config
-to the ip of your Clio server. This entry can take the form of a comma separated list if
+2. open a public, unencrypted WebSocket port on your rippled server
+3. change the IP specified in `secure_gateway` of `port_grpc` section of the rippled config
+to the IP of your Clio server. This entry can take the form of a comma-separated list if
 you are running multiple Clio nodes.
 
 Once your config files are ready, start rippled and Clio. It doesn't matter which you
@@ -84,7 +83,7 @@ the most recent ledger on the network, and then backfill. If Clio is extracting
 from rippled, and then rippled is stopped for a significant amount of time and then restarted, rippled
 will take time to backfill to the next ledger that Clio wants. The time it takes is proportional
 to the amount of time rippled was offline for. Also be aware that the amount rippled backfills
-is dependent on the online_delete and ledger_history config values; if these values
+are dependent on the online_delete and ledger_history config values; if these values
 are small, and rippled is stopped for a significant amount of time, rippled may never backfill
 to the ledger that Clio wants. To avoid this situation, it is advised to keep history
 proportional to the amount of time that you expect rippled to be offline. For example, if you
@@ -106,7 +105,7 @@ This can take some time, and depends on database throughput. With a moderately f
 database, this should take less than 10 minutes. If you did not properly set `secure_gateway`
 in the `port_grpc` section of rippled, this step will fail. Once the first ledger
 is fully downloaded, Clio only needs to extract the changed data for each ledger,
-so extraction is much faster and Clio can keep up with rippled in real time. Even under
+so extraction is much faster and Clio can keep up with rippled in real-time. Even under
 intense load, Clio should not lag behind the network, as Clio is not processing the data,
 and is simply writing to a database. The throughput of Clio is dependent on the throughput
 of your database, but a standard Cassandra or Scylla deployment can handle
@@ -140,3 +139,39 @@ are doing this, be aware that database traffic will be flowing across regions,
 which can cause high latencies. A possible alternative to this is to just deploy
 a database in each region, and the Clio nodes in each region use their region's database.
 This is effectively two systems.
+
+## Developing against `rippled` in standalone mode
+
+If you wish you develop against a `rippled` instance running in standalone
+mode there are a few quirks of both clio and rippled you need to keep in mind.
+You must:
+
+1. Advance the `rippled` ledger to at least ledger 256
+2. Wait 10 minutes before first starting clio against this standalone node.
+
+## Logging
+Clio provides several logging options, all are configurable via the config file and are detailed below.
+
+`log_level`: The minimum level of severity at which the log message will be outputted.
+Severity options are `trace`, `debug`, `info`, `warning`, `error`, `fatal`. Defaults to `info`.
+
+`log_to_console`: Enable/disable log output to console. Options are `true`/`false`. Defaults to true.
+
+`log_directory`: Path to the directory where log files are stored. If such directory doesn't exist, Clio will create it. If not specified, logs are not written to a file.
+
+`log_rotation_size`: The max size of the log file in **megabytes** before it will rotate into a smaller file. Defaults to 2GB.
+
+`log_directory_max_size`: The max size of the log directory in **megabytes** before old log files will be
+deleted to free up space. Defaults to 50GB.
+
+`log_rotation_hour_interval`: The time interval in **hours** after the last log rotation to automatically
+rotate the current log file. Defaults to 12 hours.
+
+Note, time-based log rotation occurs dependently on size-based log rotation, where if a
+size-based log rotation occurs, the timer for the time-based rotation will reset.
+
+## Cassandra / Scylla Administration
+
+Since Clio relies on either Cassandra or Scylla for its database backend, here are some important considerations:
+
+- Scylla, by default, will reserve all free RAM on a machine for itself. If you are running `rippled` or other services on the same machine, restrict its memory usage using the `--memory` argument: https://docs.scylladb.com/getting-started/scylla-in-a-shared-environment/

docker/centos/Dockerfile

@@ -0,0 +1,49 @@
+# FROM centos:7 as deps
+FROM centos:7 as build
+
+ENV CLIO_DIR=/opt/clio/
+# ENV OPENSSL_DIR=/opt/openssl
+
+RUN yum -y install git epel-release centos-release-scl perl-IPC-Cmd openssl
+RUN yum install -y devtoolset-11
+ENV version=3.16
+ENV build=3
+# RUN curl -OJL https://cmake.org/files/v$version/cmake-$version.$build.tar.gz
+COPY docker/shared/install_cmake.sh /install_cmake.sh
+RUN /install_cmake.sh 3.16.3 /usr/local
+RUN source /opt/rh/devtoolset-11/enable
+WORKDIR /tmp
+# RUN mkdir $OPENSSL_DIR && cd $OPENSSL_DIR
+COPY docker/centos/build_git_centos7.sh build_git_centos7.sh
+
+RUN ./build_git_centos7.sh
+RUN git clone https://github.com/openssl/openssl
+WORKDIR /tmp/openssl
+RUN git checkout OpenSSL_1_1_1q
+#--prefix=/usr --openssldir=/etc/ssl --libdir=lib no-shared zlib-dynamic
+RUN SSLDIR=$(openssl version -d | cut -d: -f2 | tr -d [:space:]\") && ./config -fPIC --prefix=/usr --openssldir=${SSLDIR} zlib shared && \
+    make -j $(nproc) && \
+    make install_sw
+WORKDIR /tmp
+# FROM centos:7 as build
+
+RUN git clone https://github.com/xrplf/clio.git
+COPY docker/shared/build_boost.sh build_boost.sh
+ENV OPENSSL_ROOT=/opt/local/openssl
+ENV BOOST_ROOT=/boost
+RUN source scl_source enable devtoolset-11 && /tmp/build_boost.sh 1.75.0
+RUN yum install -y bison flex
+RUN yum install -y rpmdevtools rpmlint
+RUN source /opt/rh/devtoolset-11/enable && cd /tmp/clio && \
+    cmake -B build -DBUILD_TESTS=1 && \
+    cmake --build build --parallel $(nproc)
+RUN mkdir output
+RUN strip clio/build/clio_server && strip clio/build/clio_tests
+RUN cp clio/build/clio_tests output/ && cp clio/build/clio_server output/
+RUN cp clio/example-config.json output/example-config.json
+
+FROM centos:7
+COPY --from=build /tmp/output /clio
+RUN mkdir -p /opt/clio/etc && mv /clio/example-config.json /opt/clio/etc/config.json
+
+CMD ["/clio/clio_server", "/opt/clio/etc/config.json"]

docker/centos/build_git_centos7.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+
+set -ex
+GIT_VERSION="2.37.1"
+curl -OJL https://github.com/git/git/archive/refs/tags/v${GIT_VERSION}.tar.gz
+tar zxvf git-${GIT_VERSION}.tar.gz
+cd git-${GIT_VERSION}
+
+yum install -y centos-release-scl epel-release
+yum update -y
+yum install -y devtoolset-11 autoconf gnu-getopt gettext zlib-devel  libcurl-devel
+
+source /opt/rh/devtoolset-11/enable
+make configure
+./configure
+make git -j$(nproc)
+make install git
+git  --version | cut -d ' ' -f3

docker/centos/install_cmake.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+set -eo pipefail
+
+CMAKE_VERSION=${1:-"3.16.3"}
+cd /tmp
+URL="https://github.com/Kitware/CMake/releases/download/v${CMAKE_VERSION}/cmake-${CMAKE_VERSION}-linux-x86_64.tar.gz"
+curl -OJLs $URL
+tar xzvf cmake-${CMAKE_VERSION}-Linux-x86_64.tar.gz
+mv cmake-${CMAKE_VERSION}-Linux-x86_64 /opt/
+ln -s /opt/cmake-${CMAKE_VERSION}-Linux-x86_64/bin/cmake /usr/local/bin/cmake

docker/clio_docker/centos/build_boost.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -exu
+
+#yum install wget lz4 lz4-devel git llvm13-static.x86_64 llvm13-devel.x86_64 devtoolset-11-binutils zlib-static
+# it's either those or link=static that halves the failures. probably link=static
+BOOST_VERSION=$1
+BOOST_VERSION_=$(echo ${BOOST_VERSION} | tr . _)
+echo "BOOST_VERSION: ${BOOST_VERSION}"
+echo "BOOST_VERSION_: ${BOOST_VERSION_}"
+curl -OJLs "https://boostorg.jfrog.io/artifactory/main/release/${BOOST_VERSION}/source/boost_${BOOST_VERSION_}.tar.gz"
+tar zxf "boost_${BOOST_VERSION_}.tar.gz"
+cd boost_${BOOST_VERSION_} && ./bootstrap.sh && ./b2 --without-python link=static -j$(nproc)
+mkdir -p /boost && mv boost /boost && mv stage /boost

docker/clio_docker/centos/build_git_centos7.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+
+set -ex
+GIT_VERSION="2.37.1"
+curl -OJL https://github.com/git/git/archive/refs/tags/v${GIT_VERSION}.tar.gz
+tar zxvf git-${GIT_VERSION}.tar.gz
+cd git-${GIT_VERSION}
+
+yum install -y centos-release-scl epel-release
+yum update -y
+yum install -y devtoolset-11 autoconf gnu-getopt gettext zlib-devel  libcurl-devel
+
+source /opt/rh/devtoolset-11/enable
+make configure
+./configure
+make git -j$(nproc)
+make install git
+git  --version | cut -d ' ' -f3

docker/clio_docker/centos/dockerfile

@@ -0,0 +1,34 @@
+FROM centos:7
+
+ENV CLIO_DIR=/opt/clio/
+# ENV OPENSSL_DIR=/opt/openssl
+
+RUN yum -y install git epel-release centos-release-scl perl-IPC-Cmd openssl
+RUN yum install -y devtoolset-11
+ENV version=3.16
+ENV build=3
+# RUN curl -OJL https://cmake.org/files/v$version/cmake-$version.$build.tar.gz
+COPY install_cmake.sh /install_cmake.sh
+RUN /install_cmake.sh 3.16.3 /usr/local
+RUN source /opt/rh/devtoolset-11/enable
+WORKDIR /tmp
+# RUN mkdir $OPENSSL_DIR && cd $OPENSSL_DIR
+COPY build_git_centos7.sh build_git_centos7.sh
+
+RUN ./build_git_centos7.sh
+RUN git clone https://github.com/openssl/openssl
+WORKDIR /tmp/openssl
+RUN git checkout OpenSSL_1_1_1q
+#--prefix=/usr --openssldir=/etc/ssl --libdir=lib no-shared zlib-dynamic
+RUN SSLDIR=$(openssl version -d | cut -d: -f2 | tr -d [:space:]\") && ./config -fPIC --prefix=/usr --openssldir=${SSLDIR} zlib shared && \
+    make -j $(nproc) && \
+    make install_sw
+WORKDIR /tmp
+RUN git clone https://github.com/xrplf/clio.git
+COPY build_boost.sh build_boost.sh
+ENV OPENSSL_ROOT=/opt/local/openssl
+ENV BOOST_ROOT=/boost
+RUN source scl_source enable devtoolset-11 && /tmp/build_boost.sh 1.75.0
+RUN yum install -y bison flex
+RUN source /opt/rh/devtoolset-11/enable && \
+    cd /tmp/clio && cmake -B build -Dtests=0 -Dlocal_libarchive=1 -Dunity=0 -DBUILD_TESTS=0 && cmake --build build --parallel $(nproc)

docker/clio_docker/centos/install_cmake.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+set -eo pipefail
+
+CMAKE_VERSION=${1:-"3.16.3"}
+cd /tmp
+URL="https://github.com/Kitware/CMake/releases/download/v${CMAKE_VERSION}/cmake-${CMAKE_VERSION}-linux-x86_64.tar.gz"
+curl -OJLs $URL
+tar xzvf cmake-${CMAKE_VERSION}-Linux-x86_64.tar.gz
+mv cmake-${CMAKE_VERSION}-Linux-x86_64 /opt/
+ln -s /opt/cmake-${CMAKE_VERSION}-Linux-x86_64/bin/cmake /usr/local/bin/cmake

docker/shared/build_boost.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -exu
+
+#yum install wget lz4 lz4-devel git llvm13-static.x86_64 llvm13-devel.x86_64 devtoolset-11-binutils zlib-static
+# it's either those or link=static that halves the failures. probably link=static
+BOOST_VERSION=$1
+BOOST_VERSION_=$(echo ${BOOST_VERSION} | tr . _)
+echo "BOOST_VERSION: ${BOOST_VERSION}"
+echo "BOOST_VERSION_: ${BOOST_VERSION_}"
+curl -OJLs "https://boostorg.jfrog.io/artifactory/main/release/${BOOST_VERSION}/source/boost_${BOOST_VERSION_}.tar.gz"
+tar zxf "boost_${BOOST_VERSION_}.tar.gz"
+cd boost_${BOOST_VERSION_} && ./bootstrap.sh && ./b2 --without-python link=static -j$(nproc)
+mkdir -p /boost && mv boost /boost && mv stage /boost

docker/shared/install_cmake.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+set -eo pipefail
+
+CMAKE_VERSION=${1:-"3.16.3"}
+cd /tmp
+URL="https://github.com/Kitware/CMake/releases/download/v${CMAKE_VERSION}/cmake-${CMAKE_VERSION}-linux-x86_64.tar.gz"
+curl -OJLs $URL
+tar xzvf cmake-${CMAKE_VERSION}-Linux-x86_64.tar.gz
+mv cmake-${CMAKE_VERSION}-Linux-x86_64 /opt/
+ln -s /opt/cmake-${CMAKE_VERSION}-Linux-x86_64/bin/cmake /usr/local/bin/cmake

docker/shared/install_openssl.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+set -e

docker/ubuntu/Dockerfile

@@ -0,0 +1,24 @@
+FROM ubuntu:20.04 AS boost
+
+RUN apt-get update && apt-get install -y build-essential
+ARG BOOST_VERSION_=1_75_0
+ARG BOOST_VERSION=1.75.0
+COPY docker/shared/build_boost.sh .
+RUN apt install -y curl
+RUN ./build_boost.sh ${BOOST_VERSION}
+ENV BOOST_ROOT=/boost
+
+FROM ubuntu:20.04 AS build
+ENV BOOST_ROOT=/boost
+COPY --from=boost /boost /boost
+ENV DEBIAN_FRONTEND=noninteractive
+RUN apt-get update && apt-get install --no-install-recommends -y build-essential software-properties-common pkg-config libssl-dev wget curl gpg git zlib1g-dev bison flex autoconf lsb-release
+RUN apt install -y gpg-agent
+RUN wget https://apt.llvm.org/llvm.sh
+RUN chmod +x llvm.sh && ./llvm.sh 14 && ./llvm.sh 15
+# COPY . /clio
+## Install cmake
+ARG CMAKE_VERSION=3.16.3
+COPY docker/shared/install_cmake.sh .
+RUN ./install_cmake.sh ${CMAKE_VERSION}
+ENV PATH="/opt/local/cmake/bin:$PATH"

example-config.json

@@ -30,8 +30,11 @@
         "port":51233
     },
     "log_level":"debug",
-    "log_file":"./clio.log",
-    "online_delete":0,
+    "log_to_console": true,
+    "log_directory":"./clio_log",
+    "log_rotation_size": 2048,
+    "log_directory_max_size": 51200,
+    "log_rotation_hour_interval": 12,
     "extractor_threads":8,
     "read_only":false
 }

src/backend/BackendInterface.cpp

@@ -19,7 +19,6 @@ BackendInterface::writeLedgerObject(
     std::string&& blob)
 {
     assert(key.size() == sizeof(ripple::uint256));
-    ripple::uint256 key256 = ripple::uint256::fromVoid(key.data());
     doWriteLedgerObject(std::move(key), seq, std::move(blob));
 }
 
@@ -259,7 +258,8 @@ BackendInterface::fetchLedgerPage(
         ripple::uint256 const& curCursor = keys.size() ? keys.back()
             : cursor                                   ? *cursor
                                                        : firstKey;
-        uint32_t seq = outOfOrder ? range->maxSequence : ledgerSequence;
+        std::uint32_t const seq =
+            outOfOrder ? range->maxSequence : ledgerSequence;
         auto succ = fetchSuccessorKey(curCursor, seq, yield);
         if (!succ)
             reachedEnd = true;
@@ -275,7 +275,8 @@ BackendInterface::fetchLedgerPage(
         else if (!outOfOrder)
         {
             BOOST_LOG_TRIVIAL(error)
-                << __func__ << " incorrect successor table. key = "
+                << __func__
+                << " deleted or non-existent object in successor table. key = "
                 << ripple::strHex(keys[i]) << " - seq = " << ledgerSequence;
             std::stringstream msg;
             for (size_t j = 0; j < objects.size(); ++j)
@@ -283,7 +284,6 @@ BackendInterface::fetchLedgerPage(
                 msg << " - " << ripple::strHex(keys[j]);
             }
             BOOST_LOG_TRIVIAL(error) << __func__ << msg.str();
-            assert(false);
         }
     }
     if (keys.size() && !reachedEnd)

src/backend/BackendInterface.h

@@ -162,12 +162,12 @@ public:
         std::vector<ripple::uint256> const& hashes,
         boost::asio::yield_context& yield) const = 0;
 
-    virtual AccountTransactions
+    virtual TransactionsAndCursor
     fetchAccountTransactions(
         ripple::AccountID const& account,
         std::uint32_t const limit,
         bool forward,
-        std::optional<AccountTransactionsCursor> const& cursor,
+        std::optional<TransactionsCursor> const& cursor,
         boost::asio::yield_context& yield) const = 0;
 
     virtual std::vector<TransactionAndMetadata>
@@ -180,6 +180,21 @@ public:
         std::uint32_t const ledgerSequence,
         boost::asio::yield_context& yield) const = 0;
 
+    // *** NFT methods
+    virtual std::optional<NFT>
+    fetchNFT(
+        ripple::uint256 const& tokenID,
+        std::uint32_t const ledgerSequence,
+        boost::asio::yield_context& yield) const = 0;
+
+    virtual TransactionsAndCursor
+    fetchNFTTransactions(
+        ripple::uint256 const& tokenID,
+        std::uint32_t const limit,
+        bool const forward,
+        std::optional<TransactionsCursor> const& cursorIn,
+        boost::asio::yield_context& yield) const = 0;
+
     // *** state data methods
     std::optional<Blob>
     fetchLedgerObject(
@@ -285,9 +300,15 @@ public:
         std::string&& transaction,
         std::string&& metadata) = 0;
 
+    virtual void
+    writeNFTs(std::vector<NFTsData>&& data) = 0;
+
     virtual void
     writeAccountTransactions(std::vector<AccountTransactionsData>&& data) = 0;
 
+    virtual void
+    writeNFTTransactions(std::vector<NFTTransactionsData>&& data) = 0;
+
     virtual void
     writeSuccessor(
         std::string&& key,

src/backend/CassandraBackend.cpp

@@ -1,7 +1,9 @@
+#include <ripple/app/tx/impl/details/NFTokenUtils.h>
 #include <backend/CassandraBackend.h>
 #include <backend/DBHelpers.h>
 #include <functional>
 #include <unordered_map>
+
 namespace Backend {
 
 // Type alias for async completion handlers
@@ -178,7 +180,7 @@ CassandraBackend::doWriteLedgerObject(
     if (range)
         makeAndExecuteAsyncWrite(
             this,
-            std::move(std::make_tuple(seq, key)),
+            std::make_tuple(seq, key),
             [this](auto& params) {
                 auto& [sequence, key] = params.data;
 
@@ -190,7 +192,7 @@ CassandraBackend::doWriteLedgerObject(
             "ledger_diff");
     makeAndExecuteAsyncWrite(
         this,
-        std::move(std::make_tuple(std::move(key), seq, std::move(blob))),
+        std::make_tuple(std::move(key), seq, std::move(blob)),
         [this](auto& params) {
             auto& [key, sequence, blob] = params.data;
 
@@ -215,7 +217,7 @@ CassandraBackend::writeSuccessor(
     assert(successor.size() != 0);
     makeAndExecuteAsyncWrite(
         this,
-        std::move(std::make_tuple(std::move(key), seq, std::move(successor))),
+        std::make_tuple(std::move(key), seq, std::move(successor)),
         [this](auto& params) {
             auto& [key, sequence, successor] = params.data;
 
@@ -234,7 +236,7 @@ CassandraBackend::writeLedger(
 {
     makeAndExecuteAsyncWrite(
         this,
-        std::move(std::make_tuple(ledgerInfo.seq, std::move(header))),
+        std::make_tuple(ledgerInfo.seq, std::move(header)),
         [this](auto& params) {
             auto& [sequence, header] = params.data;
             CassandraStatement statement{insertLedgerHeader_};
@@ -245,7 +247,7 @@ CassandraBackend::writeLedger(
         "ledger");
     makeAndExecuteAsyncWrite(
         this,
-        std::move(std::make_tuple(ledgerInfo.hash, ledgerInfo.seq)),
+        std::make_tuple(ledgerInfo.hash, ledgerInfo.seq),
         [this](auto& params) {
             auto& [hash, sequence] = params.data;
             CassandraStatement statement{insertLedgerHash_};
@@ -256,6 +258,7 @@ CassandraBackend::writeLedger(
         "ledger_hash");
     ledgerSequence_ = ledgerInfo.seq;
 }
+
 void
 CassandraBackend::writeAccountTransactions(
     std::vector<AccountTransactionsData>&& data)
@@ -266,11 +269,11 @@ CassandraBackend::writeAccountTransactions(
         {
             makeAndExecuteAsyncWrite(
                 this,
-                std::move(std::make_tuple(
+                std::make_tuple(
                     std::move(account),
                     record.ledgerSequence,
                     record.transactionIndex,
-                    record.txHash)),
+                    record.txHash),
                 [this](auto& params) {
                     CassandraStatement statement(insertAccountTx_);
                     auto& [account, lgrSeq, txnIdx, hash] = params.data;
@@ -283,6 +286,31 @@ CassandraBackend::writeAccountTransactions(
         }
     }
 }
+
+void
+CassandraBackend::writeNFTTransactions(std::vector<NFTTransactionsData>&& data)
+{
+    for (NFTTransactionsData const& record : data)
+    {
+        makeAndExecuteAsyncWrite(
+            this,
+            std::make_tuple(
+                record.tokenID,
+                record.ledgerSequence,
+                record.transactionIndex,
+                record.txHash),
+            [this](auto const& params) {
+                CassandraStatement statement(insertNFTTx_);
+                auto const& [tokenID, lgrSeq, txnIdx, txHash] = params.data;
+                statement.bindNextBytes(tokenID);
+                statement.bindNextIntTuple(lgrSeq, txnIdx);
+                statement.bindNextBytes(txHash);
+                return statement;
+            },
+            "nf_token_transactions");
+    }
+}
+
 void
 CassandraBackend::writeTransaction(
     std::string&& hash,
@@ -296,7 +324,7 @@ CassandraBackend::writeTransaction(
 
     makeAndExecuteAsyncWrite(
         this,
-        std::move(std::make_pair(seq, hash)),
+        std::make_pair(seq, hash),
         [this](auto& params) {
             CassandraStatement statement{insertLedgerTransaction_};
             statement.bindNextInt(params.data.first);
@@ -306,12 +334,12 @@ CassandraBackend::writeTransaction(
         "ledger_transaction");
     makeAndExecuteAsyncWrite(
         this,
-        std::move(std::make_tuple(
+        std::make_tuple(
             std::move(hash),
             seq,
             date,
             std::move(transaction),
-            std::move(metadata))),
+            std::move(metadata)),
         [this](auto& params) {
             CassandraStatement statement{insertTransaction_};
             auto& [hash, sequence, date, transaction, metadata] = params.data;
@@ -325,6 +353,43 @@ CassandraBackend::writeTransaction(
         "transaction");
 }
 
+void
+CassandraBackend::writeNFTs(std::vector<NFTsData>&& data)
+{
+    for (NFTsData const& record : data)
+    {
+        makeAndExecuteAsyncWrite(
+            this,
+            std::make_tuple(
+                record.tokenID,
+                record.ledgerSequence,
+                record.owner,
+                record.isBurned),
+            [this](auto const& params) {
+                CassandraStatement statement{insertNFT_};
+                auto const& [tokenID, lgrSeq, owner, isBurned] = params.data;
+                statement.bindNextBytes(tokenID);
+                statement.bindNextInt(lgrSeq);
+                statement.bindNextBytes(owner);
+                statement.bindNextBoolean(isBurned);
+                return statement;
+            },
+            "nf_tokens");
+
+        makeAndExecuteAsyncWrite(
+            this,
+            std::make_tuple(record.tokenID),
+            [this](auto const& params) {
+                CassandraStatement statement{insertIssuerNFT_};
+                auto const& [tokenID] = params.data;
+                statement.bindNextBytes(ripple::nft::getIssuer(tokenID));
+                statement.bindNextBytes(tokenID);
+                return statement;
+            },
+            "issuer_nf_tokens");
+    }
+}
+
 std::optional<LedgerRange>
 CassandraBackend::hardFetchLedgerRange(boost::asio::yield_context& yield) const
 {
@@ -502,21 +567,119 @@ CassandraBackend::fetchAllTransactionHashesInLedger(
     return hashes;
 }
 
-AccountTransactions
+std::optional<NFT>
+CassandraBackend::fetchNFT(
+    ripple::uint256 const& tokenID,
+    std::uint32_t const ledgerSequence,
+    boost::asio::yield_context& yield) const
+{
+    CassandraStatement statement{selectNFT_};
+    statement.bindNextBytes(tokenID);
+    statement.bindNextInt(ledgerSequence);
+    CassandraResult response = executeAsyncRead(statement, yield);
+    if (!response)
+        return {};
+
+    NFT result;
+    result.tokenID = tokenID;
+    result.ledgerSequence = response.getUInt32();
+    result.owner = response.getBytes();
+    result.isBurned = response.getBool();
+    return result;
+}
+
+TransactionsAndCursor
+CassandraBackend::fetchNFTTransactions(
+    ripple::uint256 const& tokenID,
+    std::uint32_t const limit,
+    bool const forward,
+    std::optional<TransactionsCursor> const& cursorIn,
+    boost::asio::yield_context& yield) const
+{
+    auto cursor = cursorIn;
+    auto rng = fetchLedgerRange();
+    if (!rng)
+        return {{}, {}};
+
+    CassandraStatement statement = forward
+        ? CassandraStatement(selectNFTTxForward_)
+        : CassandraStatement(selectNFTTx_);
+
+    statement.bindNextBytes(tokenID);
+
+    if (cursor)
+    {
+        statement.bindNextIntTuple(
+            cursor->ledgerSequence, cursor->transactionIndex);
+        BOOST_LOG_TRIVIAL(debug) << " token_id = " << ripple::strHex(tokenID)
+                                 << " tuple = " << cursor->ledgerSequence
+                                 << " : " << cursor->transactionIndex;
+    }
+    else
+    {
+        int const seq = forward ? rng->minSequence : rng->maxSequence;
+        int const placeHolder =
+            forward ? 0 : std::numeric_limits<std::uint32_t>::max();
+
+        statement.bindNextIntTuple(placeHolder, placeHolder);
+        BOOST_LOG_TRIVIAL(debug)
+            << " token_id = " << ripple::strHex(tokenID) << " idx = " << seq
+            << " tuple = " << placeHolder;
+    }
+
+    statement.bindNextUInt(limit);
+
+    CassandraResult result = executeAsyncRead(statement, yield);
+
+    if (!result.hasResult())
+    {
+        BOOST_LOG_TRIVIAL(debug) << __func__ << " - no rows returned";
+        return {};
+    }
+
+    std::vector<ripple::uint256> hashes = {};
+    auto numRows = result.numRows();
+    BOOST_LOG_TRIVIAL(info) << "num_rows = " << numRows;
+    do
+    {
+        hashes.push_back(result.getUInt256());
+        if (--numRows == 0)
+        {
+            BOOST_LOG_TRIVIAL(debug) << __func__ << " setting cursor";
+            auto const [lgrSeq, txnIdx] = result.getInt64Tuple();
+            cursor = {
+                static_cast<std::uint32_t>(lgrSeq),
+                static_cast<std::uint32_t>(txnIdx)};
+
+            if (forward)
+                ++cursor->transactionIndex;
+        }
+    } while (result.nextRow());
+
+    auto txns = fetchTransactions(hashes, yield);
+    BOOST_LOG_TRIVIAL(debug) << __func__ << " txns = " << txns.size();
+
+    if (txns.size() == limit)
+    {
+        BOOST_LOG_TRIVIAL(debug) << __func__ << " returning cursor";
+        return {txns, cursor};
+    }
+
+    return {txns, {}};
+}
+
+TransactionsAndCursor
 CassandraBackend::fetchAccountTransactions(
     ripple::AccountID const& account,
     std::uint32_t const limit,
     bool const forward,
-    std::optional<AccountTransactionsCursor> const& cursorIn,
+    std::optional<TransactionsCursor> const& cursorIn,
     boost::asio::yield_context& yield) const
 {
     auto rng = fetchLedgerRange();
     if (!rng)
         return {{}, {}};
 
-    auto keylet = ripple::keylet::account(account);
-    auto cursor = cursorIn;
-
     CassandraStatement statement = [this, forward]() {
         if (forward)
             return CassandraStatement{selectAccountTxForward_};
@@ -524,6 +687,7 @@ CassandraBackend::fetchAccountTransactions(
             return CassandraStatement{selectAccountTx_};
     }();
 
+    auto cursor = cursorIn;
     statement.bindNextBytes(account);
     if (cursor)
     {
@@ -535,8 +699,8 @@ CassandraBackend::fetchAccountTransactions(
     }
     else
     {
-        int seq = forward ? rng->minSequence : rng->maxSequence;
-        int placeHolder =
+        int const seq = forward ? rng->minSequence : rng->maxSequence;
+        int const placeHolder =
             forward ? 0 : std::numeric_limits<std::uint32_t>::max();
 
         statement.bindNextIntTuple(placeHolder, placeHolder);
@@ -584,6 +748,7 @@ CassandraBackend::fetchAccountTransactions(
 
     return {txns, {}};
 }
+
 std::optional<ripple::uint256>
 CassandraBackend::doFetchSuccessorKey(
     ripple::uint256 key,
@@ -895,8 +1060,8 @@ CassandraBackend::open(bool readOnly)
         cass_cluster_set_credentials(
             cluster, username.c_str(), getString("password").c_str());
     }
-    int threads = getInt("threads") ? *getInt("threads")
-                                    : std::thread::hardware_concurrency();
+    int threads =
+        getInt("threads").value_or(std::thread::hardware_concurrency());
 
     rc = cass_cluster_set_num_threads_io(cluster, threads);
     if (rc != CASS_OK)
@@ -1179,6 +1344,64 @@ CassandraBackend::open(bool readOnly)
               << " LIMIT 1";
         if (!executeSimpleStatement(query.str()))
             continue;
+
+        query.str("");
+        query << "CREATE TABLE IF NOT EXISTS " << tablePrefix << "nf_tokens"
+              << "  ("
+              << "    token_id blob,"
+              << "    sequence bigint,"
+              << "    owner blob,"
+              << "    is_burned boolean,"
+              << "    PRIMARY KEY (token_id, sequence)"
+              << "  )"
+              << "  WITH CLUSTERING ORDER BY (sequence DESC)"
+              << "    AND default_time_to_live = " << ttl;
+        if (!executeSimpleStatement(query.str()))
+            continue;
+
+        query.str("");
+        query << "SELECT * FROM " << tablePrefix << "nf_tokens"
+              << " LIMIT 1";
+        if (!executeSimpleStatement(query.str()))
+            continue;
+
+        query.str("");
+        query << "CREATE TABLE IF NOT EXISTS " << tablePrefix
+              << "issuer_nf_tokens"
+              << "  ("
+              << "    issuer blob,"
+              << "    token_id blob,"
+              << "    PRIMARY KEY (issuer, token_id)"
+              << "  )";
+        if (!executeSimpleStatement(query.str()))
+            continue;
+
+        query.str("");
+        query << "SELECT * FROM " << tablePrefix << "issuer_nf_tokens"
+              << " LIMIT 1";
+        if (!executeSimpleStatement(query.str()))
+            continue;
+
+        query.str("");
+        query << "CREATE TABLE IF NOT EXISTS " << tablePrefix
+              << "nf_token_transactions"
+              << "  ("
+              << "    token_id blob,"
+              << "    seq_idx tuple<bigint, bigint>,"
+              << "    hash blob,"
+              << "    PRIMARY KEY (token_id, seq_idx)"
+              << "  )"
+              << "  WITH CLUSTERING ORDER BY (seq_idx DESC)"
+              << "    AND default_time_to_live = " << ttl;
+        if (!executeSimpleStatement(query.str()))
+            continue;
+
+        query.str("");
+        query << "SELECT * FROM " << tablePrefix << "nf_token_transactions"
+              << " LIMIT 1";
+        if (!executeSimpleStatement(query.str()))
+            continue;
+
         setupSessionAndTable = true;
     }
 
@@ -1296,6 +1519,57 @@ CassandraBackend::open(bool readOnly)
         if (!selectAccountTxForward_.prepareStatement(query, session_.get()))
             continue;
 
+        query.str("");
+        query << "INSERT INTO " << tablePrefix << "nf_tokens"
+              << " (token_id,sequence,owner,is_burned)"
+              << " VALUES (?,?,?,?)";
+        if (!insertNFT_.prepareStatement(query, session_.get()))
+            continue;
+
+        query.str("");
+        query << "SELECT sequence,owner,is_burned"
+              << " FROM " << tablePrefix << "nf_tokens WHERE"
+              << " token_id = ? AND"
+              << " sequence <= ?"
+              << " ORDER BY sequence DESC"
+              << " LIMIT 1";
+        if (!selectNFT_.prepareStatement(query, session_.get()))
+            continue;
+
+        query.str("");
+        query << "INSERT INTO " << tablePrefix << "issuer_nf_tokens"
+              << " (issuer,token_id)"
+              << " VALUES (?,?)";
+        if (!insertIssuerNFT_.prepareStatement(query, session_.get()))
+            continue;
+
+        query.str("");
+        query << "INSERT INTO " << tablePrefix << "nf_token_transactions"
+              << " (token_id,seq_idx,hash)"
+              << " VALUES (?,?,?)";
+        if (!insertNFTTx_.prepareStatement(query, session_.get()))
+            continue;
+
+        query.str("");
+        query << "SELECT hash,seq_idx"
+              << " FROM " << tablePrefix << "nf_token_transactions WHERE"
+              << " token_id = ? AND"
+              << " seq_idx < ?"
+              << " ORDER BY seq_idx DESC"
+              << " LIMIT ?";
+        if (!selectNFTTx_.prepareStatement(query, session_.get()))
+            continue;
+
+        query.str("");
+        query << "SELECT hash,seq_idx"
+              << " FROM " << tablePrefix << "nf_token_transactions WHERE"
+              << " token_id = ? AND"
+              << " seq_idx >= ?"
+              << " ORDER BY seq_idx ASC"
+              << " LIMIT ?";
+        if (!selectNFTTxForward_.prepareStatement(query, session_.get()))
+            continue;
+
         query.str("");
         query << " INSERT INTO " << tablePrefix << "ledgers "
               << " (sequence, header) VALUES(?,?)";

src/backend/CassandraBackend.h

@@ -115,7 +115,7 @@ public:
             throw std::runtime_error(
                 "CassandraStatement::bindNextBoolean - statement_ is null");
         CassError rc = cass_statement_bind_bool(
-            statement_, 1, static_cast<cass_bool_t>(val));
+            statement_, curBindingIndex_, static_cast<cass_bool_t>(val));
         if (rc != CASS_OK)
         {
             std::stringstream ss;
@@ -481,6 +481,33 @@ public:
         return {first, second};
     }
 
+    // TODO: should be replaced with a templated implementation as is very
+    // similar to other getters
+    bool
+    getBool()
+    {
+        if (!row_)
+        {
+            std::stringstream msg;
+            msg << __func__ << " - no result";
+            BOOST_LOG_TRIVIAL(error) << msg.str();
+            throw std::runtime_error(msg.str());
+        }
+        cass_bool_t val;
+        CassError rc =
+            cass_value_get_bool(cass_row_get_column(row_, curGetIndex_), &val);
+        if (rc != CASS_OK)
+        {
+            std::stringstream msg;
+            msg << __func__ << " - error getting value: " << rc << ", "
+                << cass_error_desc(rc);
+            BOOST_LOG_TRIVIAL(error) << msg.str();
+            throw std::runtime_error(msg.str());
+        }
+        ++curGetIndex_;
+        return val;
+    }
+
     ~CassandraResult()
     {
         if (result_ != nullptr)
@@ -599,6 +626,12 @@ private:
     CassandraPreparedStatement insertAccountTx_;
     CassandraPreparedStatement selectAccountTx_;
     CassandraPreparedStatement selectAccountTxForward_;
+    CassandraPreparedStatement insertNFT_;
+    CassandraPreparedStatement selectNFT_;
+    CassandraPreparedStatement insertIssuerNFT_;
+    CassandraPreparedStatement insertNFTTx_;
+    CassandraPreparedStatement selectNFTTx_;
+    CassandraPreparedStatement selectNFTTxForward_;
     CassandraPreparedStatement insertLedgerHeader_;
     CassandraPreparedStatement insertLedgerHash_;
     CassandraPreparedStatement updateLedgerRange_;
@@ -615,9 +648,6 @@ private:
     // maximum number of concurrent in flight requests. New requests will wait
     // for earlier requests to finish if this limit is exceeded
     std::uint32_t maxRequestsOutstanding = 10000;
-    // we keep this small because the indexer runs in the background, and we
-    // don't want the database to be swamped when the indexer is running
-    std::uint32_t indexerMaxRequestsOutstanding = 10;
     mutable std::atomic_uint32_t numRequestsOutstanding_ = 0;
 
     // mutex and condition_variable to limit the number of concurrent in flight
@@ -683,12 +713,12 @@ public:
         open_ = false;
     }
 
-    AccountTransactions
+    TransactionsAndCursor
     fetchAccountTransactions(
         ripple::AccountID const& account,
         std::uint32_t const limit,
         bool forward,
-        std::optional<AccountTransactionsCursor> const& cursor,
+        std::optional<TransactionsCursor> const& cursor,
         boost::asio::yield_context& yield) const override;
 
     bool
@@ -852,6 +882,20 @@ public:
         std::uint32_t const ledgerSequence,
         boost::asio::yield_context& yield) const override;
 
+    std::optional<NFT>
+    fetchNFT(
+        ripple::uint256 const& tokenID,
+        std::uint32_t const ledgerSequence,
+        boost::asio::yield_context& yield) const override;
+
+    TransactionsAndCursor
+    fetchNFTTransactions(
+        ripple::uint256 const& tokenID,
+        std::uint32_t const limit,
+        bool const forward,
+        std::optional<TransactionsCursor> const& cursorIn,
+        boost::asio::yield_context& yield) const override;
+
     // Synchronously fetch the object with key key, as of ledger with sequence
     // sequence
     std::optional<Blob>
@@ -941,6 +985,9 @@ public:
     writeAccountTransactions(
         std::vector<AccountTransactionsData>&& data) override;
 
+    void
+    writeNFTTransactions(std::vector<NFTTransactionsData>&& data) override;
+
     void
     writeTransaction(
         std::string&& hash,
@@ -949,6 +996,9 @@ public:
         std::string&& transaction,
         std::string&& metadata) override;
 
+    void
+    writeNFTs(std::vector<NFTsData>&& data) override;
+
     void
     startWrites() const override
     {
@@ -1014,6 +1064,7 @@ public:
     {
         return numRequestsOutstanding_ < maxRequestsOutstanding;
     }
+
     inline bool
     finishedAllRequests() const
     {

src/backend/DBHelpers.h

@@ -9,8 +9,8 @@
 #include <backend/Pg.h>
 #include <backend/Types.h>
 
-/// Struct used to keep track of what to write to transactions and
-/// account_transactions tables in Postgres
+/// Struct used to keep track of what to write to
+/// account_transactions/account_tx tables
 struct AccountTransactionsData
 {
     boost::container::flat_set<ripple::AccountID> accounts;
@@ -32,6 +32,57 @@ struct AccountTransactionsData
     AccountTransactionsData() = default;
 };
 
+/// Represents a link from a tx to an NFT that was targeted/modified/created
+/// by it. Gets written to nf_token_transactions table and the like.
+struct NFTTransactionsData
+{
+    ripple::uint256 tokenID;
+    std::uint32_t ledgerSequence;
+    std::uint32_t transactionIndex;
+    ripple::uint256 txHash;
+
+    NFTTransactionsData(
+        ripple::uint256 const& tokenID,
+        ripple::TxMeta const& meta,
+        ripple::uint256 const& txHash)
+        : tokenID(tokenID)
+        , ledgerSequence(meta.getLgrSeq())
+        , transactionIndex(meta.getIndex())
+        , txHash(txHash)
+    {
+    }
+};
+
+/// Represents an NFT state at a particular ledger. Gets written to nf_tokens
+/// table and the like.
+struct NFTsData
+{
+    ripple::uint256 tokenID;
+    std::uint32_t ledgerSequence;
+
+    // The transaction index is only stored because we want to store only the
+    // final state of an NFT per ledger. Since we pull this from transactions
+    // we keep track of which tx index created this so we can de-duplicate, as
+    // it is possible for one ledger to have multiple txs that change the
+    // state of the same NFT.
+    std::uint32_t transactionIndex;
+    ripple::AccountID owner;
+    bool isBurned;
+
+    NFTsData(
+        ripple::uint256 const& tokenID,
+        ripple::AccountID const& owner,
+        ripple::TxMeta const& meta,
+        bool isBurned)
+        : tokenID(tokenID)
+        , ledgerSequence(meta.getLgrSeq())
+        , transactionIndex(meta.getIndex())
+        , owner(owner)
+        , isBurned(isBurned)
+    {
+    }
+};
+
 template <class T>
 inline bool
 isOffer(T const& object)

src/backend/LayeredCache.cpp

@@ -1,110 +0,0 @@
-#include <backend/LayeredCache.h>
-namespace Backend {
-
-void
-LayeredCache::insert(
-    ripple::uint256 const& key,
-    Blob const& value,
-    uint32_t seq)
-{
-    auto entry = map_[key];
-    // stale insert, do nothing
-    if (seq <= entry.recent.seq)
-        return;
-    entry.old = entry.recent;
-    entry.recent = {seq, value};
-    if (value.empty())
-        pendingDeletes_.push_back(key);
-    if (!entry.old.blob.empty())
-        pendingSweeps_.push_back(key);
-}
-
-std::optional<Blob>
-LayeredCache::select(CacheEntry const& entry, uint32_t seq) const
-{
-    if (seq < entry.old.seq)
-        return {};
-    if (seq < entry.recent.seq && !entry.old.blob.empty())
-        return entry.old.blob;
-    if (!entry.recent.blob.empty())
-        return entry.recent.blob;
-    return {};
-}
-void
-LayeredCache::update(std::vector<LedgerObject> const& blobs, uint32_t seq)
-{
-    std::unique_lock lck{mtx_};
-    if (seq > mostRecentSequence_)
-        mostRecentSequence_ = seq;
-    for (auto const& k : pendingSweeps_)
-    {
-        auto e = map_[k];
-        e.old = {};
-    }
-    for (auto const& k : pendingDeletes_)
-    {
-        map_.erase(k);
-    }
-    for (auto const& b : blobs)
-    {
-        insert(b.key, b.blob, seq);
-    }
-}
-std::optional<LedgerObject>
-LayeredCache::getSuccessor(ripple::uint256 const& key, uint32_t seq) const
-{
-    ripple::uint256 curKey = key;
-    while (true)
-    {
-        std::shared_lock lck{mtx_};
-        if (seq < mostRecentSequence_ - 1)
-            return {};
-        auto e = map_.upper_bound(curKey);
-        if (e == map_.end())
-            return {};
-        auto const& entry = e->second;
-        auto blob = select(entry, seq);
-        if (!blob)
-        {
-            curKey = e->first;
-            continue;
-        }
-        else
-            return {{e->first, *blob}};
-    }
-}
-std::optional<LedgerObject>
-LayeredCache::getPredecessor(ripple::uint256 const& key, uint32_t seq) const
-{
-    ripple::uint256 curKey = key;
-    std::shared_lock lck{mtx_};
-    while (true)
-    {
-        if (seq < mostRecentSequence_ - 1)
-            return {};
-        auto e = map_.lower_bound(curKey);
-        --e;
-        if (e == map_.begin())
-            return {};
-        auto const& entry = e->second;
-        auto blob = select(entry, seq);
-        if (!blob)
-        {
-            curKey = e->first;
-            continue;
-        }
-        else
-            return {{e->first, *blob}};
-    }
-}
-std::optional<Blob>
-LayeredCache::get(ripple::uint256 const& key, uint32_t seq) const
-{
-    std::shared_lock lck{mtx_};
-    auto e = map_.find(key);
-    if (e == map_.end())
-        return {};
-    auto const& entry = e->second;
-    return select(entry, seq);
-}
-}  // namespace Backend

src/backend/LayeredCache.h

@@ -1,73 +0,0 @@
-#ifndef CLIO_LAYEREDCACHE_H_INCLUDED
-#define CLIO_LAYEREDCACHE_H_INCLUDED
-
-#include <ripple/basics/base_uint.h>
-#include <backend/Types.h>
-#include <map>
-#include <mutex>
-#include <shared_mutex>
-#include <utility>
-#include <vector>
-namespace Backend {
-class LayeredCache
-{
-    struct SeqBlobPair
-    {
-        uint32_t seq;
-        Blob blob;
-    };
-    struct CacheEntry
-    {
-        SeqBlobPair recent;
-        SeqBlobPair old;
-    };
-
-    std::map<ripple::uint256, CacheEntry> map_;
-    std::vector<ripple::uint256> pendingDeletes_;
-    std::vector<ripple::uint256> pendingSweeps_;
-    mutable std::shared_mutex mtx_;
-    uint32_t mostRecentSequence_;
-
-    void
-    insert(ripple::uint256 const& key, Blob const& value, uint32_t seq);
-
-    /*
-    void
-    insert(ripple::uint256 const& key, Blob const& value, uint32_t seq)
-    {
-        map_.emplace(key,{{seq,value,{}});
-    }
-    void
-    update(ripple::uint256 const& key, Blob const& value, uint32_t seq)
-    {
-            auto& entry = map_.find(key);
-            entry.old = entry.recent;
-            entry.recent = {seq, value};
-            pendingSweeps_.push_back(key);
-    }
-    void
-    erase(ripple::uint256 const& key, uint32_t seq)
-    {
-            update(key, {}, seq);
-            pendingDeletes_.push_back(key);
-    }
-    */
-    std::optional<Blob>
-    select(CacheEntry const& entry, uint32_t seq) const;
-
-public:
-    void
-    update(std::vector<LedgerObject> const& blobs, uint32_t seq);
-
-    std::optional<Blob>
-    get(ripple::uint256 const& key, uint32_t seq) const;
-
-    std::optional<LedgerObject>
-    getSuccessor(ripple::uint256 const& key, uint32_t seq) const;
-
-    std::optional<LedgerObject>
-    getPredecessor(ripple::uint256 const& key, uint32_t seq) const;
-};
-
-}  // namespace Backend
-#endif

src/backend/Pg.cpp

@@ -833,7 +833,7 @@ PgPool::checkout()
         else if (connections_ < config_.max_connections)
         {
             ++connections_;
-            ret = std::make_unique<Pg>(config_, ioc_, stop_, mutex_);
+            ret = std::make_unique<Pg>(config_, ioc_);
         }
         // Otherwise, wait until a connection becomes available or we stop.
         else
@@ -1680,7 +1680,6 @@ getLedger(
         whichLedger,
     std::shared_ptr<PgPool>& pgPool)
 {
-    ripple::LedgerInfo lgrInfo;
     std::stringstream sql;
     sql << "SELECT ledger_hash, prev_hash, account_set_hash, trans_set_hash, "
            "total_coins, closing_time, prev_closing_time, close_time_res, "

src/backend/Pg.h

@@ -262,8 +262,6 @@ class Pg
 
     PgConfig const& config_;
     boost::asio::io_context::strand strand_;
-    bool& stop_;
-    std::mutex& mutex_;
 
     asio_socket_type socket_{nullptr, [](boost::asio::ip::tcp::socket*) {}};
 
@@ -364,14 +362,9 @@ public:
      *
      * @param config Config parameters.
      * @param j Logger object.
-     * @param stop Reference to connection pool's stop flag.
-     * @param mutex Reference to connection pool's mutex.
      */
-    Pg(PgConfig const& config,
-       boost::asio::io_context& ctx,
-       bool& stop,
-       std::mutex& mutex)
-        : config_(config), strand_(ctx), stop_(stop), mutex_(mutex)
+    Pg(PgConfig const& config, boost::asio::io_context& ctx)
+        : config_(config), strand_(ctx)
     {
     }
 };

src/backend/PostgresBackend.cpp

@@ -2,6 +2,7 @@
 #include <boost/format.hpp>
 #include <backend/PostgresBackend.h>
 #include <thread>
+
 namespace Backend {
 
 // Type alias for async completion handlers
@@ -77,6 +78,12 @@ PostgresBackend::writeAccountTransactions(
     }
 }
 
+void
+PostgresBackend::writeNFTTransactions(std::vector<NFTTransactionsData>&& data)
+{
+    throw std::runtime_error("Not implemented");
+}
+
 void
 PostgresBackend::doWriteLedgerObject(
     std::string&& key,
@@ -152,6 +159,12 @@ PostgresBackend::writeTransaction(
                         << '\t' << "\\\\x" << ripple::strHex(metadata) << '\n';
 }
 
+void
+PostgresBackend::writeNFTs(std::vector<NFTsData>&& data)
+{
+    throw std::runtime_error("Not implemented");
+}
+
 std::uint32_t
 checkResult(PgResult const& res, std::uint32_t const numFieldsExpected)
 {
@@ -419,6 +432,15 @@ PostgresBackend::fetchAllTransactionHashesInLedger(
     return {};
 }
 
+std::optional<NFT>
+PostgresBackend::fetchNFT(
+    ripple::uint256 const& tokenID,
+    std::uint32_t const ledgerSequence,
+    boost::asio::yield_context& yield) const
+{
+    throw std::runtime_error("Not implemented");
+}
+
 std::optional<ripple::uint256>
 PostgresBackend::doFetchSuccessorKey(
     ripple::uint256 key,
@@ -637,12 +659,25 @@ PostgresBackend::fetchLedgerDiff(
     return {};
 }
 
-AccountTransactions
+// TODO this implementation and fetchAccountTransactions should be
+// generalized
+TransactionsAndCursor
+PostgresBackend::fetchNFTTransactions(
+    ripple::uint256 const& tokenID,
+    std::uint32_t const limit,
+    bool forward,
+    std::optional<TransactionsCursor> const& cursor,
+    boost::asio::yield_context& yield) const
+{
+    throw std::runtime_error("Not implemented");
+}
+
+TransactionsAndCursor
 PostgresBackend::fetchAccountTransactions(
     ripple::AccountID const& account,
     std::uint32_t const limit,
     bool forward,
-    std::optional<AccountTransactionsCursor> const& cursor,
+    std::optional<TransactionsCursor> const& cursor,
     boost::asio::yield_context& yield) const
 {
     PgQuery pgQuery(pgPool_);

src/backend/PostgresBackend.h

@@ -62,6 +62,20 @@ public:
         std::uint32_t const ledgerSequence,
         boost::asio::yield_context& yield) const override;
 
+    std::optional<NFT>
+    fetchNFT(
+        ripple::uint256 const& tokenID,
+        std::uint32_t const ledgerSequence,
+        boost::asio::yield_context& yield) const override;
+
+    TransactionsAndCursor
+    fetchNFTTransactions(
+        ripple::uint256 const& tokenID,
+        std::uint32_t const limit,
+        bool const forward,
+        std::optional<TransactionsCursor> const& cursorIn,
+        boost::asio::yield_context& yield) const override;
+
     std::vector<LedgerObject>
     fetchLedgerDiff(
         std::uint32_t const ledgerSequence,
@@ -87,12 +101,12 @@ public:
         std::uint32_t const sequence,
         boost::asio::yield_context& yield) const override;
 
-    AccountTransactions
+    TransactionsAndCursor
     fetchAccountTransactions(
         ripple::AccountID const& account,
         std::uint32_t const limit,
         bool forward,
-        std::optional<AccountTransactionsCursor> const& cursor,
+        std::optional<TransactionsCursor> const& cursor,
         boost::asio::yield_context& yield) const override;
 
     void
@@ -120,10 +134,16 @@ public:
         std::string&& transaction,
         std::string&& metadata) override;
 
+    void
+    writeNFTs(std::vector<NFTsData>&& data) override;
+
     void
     writeAccountTransactions(
         std::vector<AccountTransactionsData>&& data) override;
 
+    void
+    writeNFTTransactions(std::vector<NFTTransactionsData>&& data) override;
+
     void
     open(bool readOnly) override;
 

src/backend/README.md

@@ -1,174 +1,132 @@
-The data model used by clio is different than that used by rippled.
-rippled uses what is known as a SHAMap, which is a tree structure, with
-actual ledger and transaction data at the leaves of the tree. Looking up a record
-is a tree traversal, where the key is used to determine the path to the proper
-leaf node. The path from root to leaf is used as a proof-tree on the p2p network,
-where nodes can prove that a piece of data is present in a ledger by sending
-the path from root to leaf. Other nodes can verify this path and be certain
-that the data does actually exist in the ledger in question.
+# Clio Backend
+## Background
+The backend of Clio is responsible for handling the proper reading and writing of past ledger data from and to a given database. As of right now, Cassandra is the only supported database that is production-ready. However, support for more databases like PostgreSQL and DynamoDB may be added in future versions. Support for database types can be easily extended by creating new implementations which implements the virtual methods of `BackendInterface.h`. Then, use the Factory Object Design Pattern to simply add logic statements to `BackendFactory.h` that return the new database interface for a specific `type` in Clio's configuration file. 
 
-clio instead flattens the data model, so lookups are O(1). This results in time
-and space savings. This is possible because clio does not participate in the peer
-to peer protocol, and thus does not need to verify any data. clio fully trusts the
-rippled nodes that are being used as a data source.
+## Data Model
+The data model used by Clio to read and write ledger data is different from what Rippled uses. Rippled uses a novel data structure named [*SHAMap*](https://github.com/ripple/rippled/blob/master/src/ripple/shamap/README.md), which is a combination of a Merkle Tree and a Radix Trie. In a SHAMap, ledger objects are stored in the root vertices of the tree. Thus, looking up a record located at the leaf node of the SHAMap executes a tree search, where the path from the root node to the leaf node is the key of the record. Rippled nodes can also generate a proof-tree by forming a subtree with all the path nodes and their neighbors, which can then be used to prove the existnce of the leaf node data to other Rippled nodes. In short, the main purpose of the SHAMap data structure is to facilitate the fast validation of data integrity between different decentralized Rippled nodes.
 
-clio uses certain features of database query languages to make this happen. Many
-databases provide the necessary features to implement the clio data model. At the
-time of writing, the data model is implemented in PostgreSQL and CQL (the query
-language used by Apache Cassandra and ScyllaDB).
+Since Clio only extracts past validated ledger data from a group of trusted Rippled nodes, it can be safely assumed that these ledger data are correct without the need to validate with other  nodes in the XRP peer-to-peer network. Because of this, Clio is able to use a flattened data model to store the past validated ledger data, which allows for direct record lookup with much faster constant time operations. 
 
-The below examples are a sort of pseudo query language
+There are three main types of data in each XRP ledger version, they are [Ledger Header](https://xrpl.org/ledger-header.html), [Transaction Set](https://xrpl.org/transaction-formats.html) and [State Data](https://xrpl.org/ledger-object-types.html). Due to the structural differences of the different types of databases, Clio may choose to represent these data using a different schema for each unique database type. 
 
-## Ledgers
+**Keywords**  
+*Sequence*: A unique incrementing identification number used to label the different ledger versions.  
+*Hash*: The SHA512-half (calculate SHA512 and take the first 256 bits) hash of various ledger data like the entire ledger or specific ledger objects.
+*Ledger Object*: The [binary-encoded](https://xrpl.org/serialization.html) STObject containing specific data (i.e. metadata, transaction data).  
+*Metadata*: The data containing [detailed information](https://xrpl.org/transaction-metadata.html#transaction-metadata) of the outcome of a specific transaction, regardless of whether the transaction was successful.  
+*Transaction data*: The data containing the [full details](https://xrpl.org/transaction-common-fields.html) of a specific transaction.  
+*Object Index*: The pseudo-random unique identifier of a ledger object, created by hashing the data of the object.  
 
-We store ledger headers in a ledgers table. In PostgreSQL, we store
-the headers in their deserialized form, so we can look up by sequence or hash.
+## Cassandra Implementation
+Cassandra is a distributed wide-column NoSQL database designed to handle large data throughput with high availability and no single point of failure. By leveraging Cassandra, Clio will be able to quickly and reliably scale up when needed simply by adding more Cassandra nodes to the Cassandra cluster configuration.
 
-In Cassandra, we store the headers as blobs. The primary table maps a ledger sequence
-to the blob, and a secondary table maps a ledger hash to a ledger sequence.
+In Cassandra, Clio will be creating 9 tables to store the ledger data, they are `ledger_transactions`, `transactions`, `ledger_hashes`, `ledger_range`, `objects`, `ledgers`, `diff`, `account_tx`, and `successor`.  Their schemas and how they work are detailed below.
 
-## Transactions
-Transactions are stored in a very basic table, with a schema like so:
+*Note, if you would like visually explore the data structure of the Cassandra database, you can first run Clio server with database `type` configured as `cassandra` to fill ledger data from Rippled nodes into Cassandra, then use a GUI database management tool like [Datastax's Opcenter](https://docs.datastax.com/en/install/6.0/install/opscInstallOpsc.html) to interactively view it.* 
 
+
+### `ledger_transactions`
 ```
-CREATE TABLE transactions (
-hash blob,
-ledger_sequence int,
-transaction blob,
-PRIMARY KEY(hash))
+CREATE TABLE clio.ledger_transactions (  
+	ledger_sequence bigint,  # The sequence number of the ledger version
+	hash blob,               # Hash of all the transactions on this ledger version
+	PRIMARY KEY (ledger_sequence, hash)  
+) WITH CLUSTERING ORDER BY (hash ASC) ...
+ ```
+This table stores the hashes of all transactions in a given ledger sequence ordered by the hash value in ascending order. 
+
+### `transactions`
 ```
-The primary key is the hash.
+CREATE TABLE clio.transactions (  
+	hash blob PRIMARY KEY,   # The transaction hash
+	date bigint,             # Date of the transaction
+	ledger_sequence bigint,  # The sequence that the transaction was validated
+	metadata blob,           # Metadata of the transaction
+	transaction blob         # Data of the transaction
+) ...
+ ```
+This table stores the full transaction and metadata of each ledger version with the transaction hash as the primary key.
 
-A common query pattern is fetching all transactions in a ledger. In PostgreSQL,
-nothing special is needed for this. We just query:
+To look up all the transactions that were validated in a ledger version with sequence `n`, one can first get the all the transaction hashes in that ledger version by querying `SELECT * FROM ledger_transactions WHERE ledger_sequence = n;`. Then, iterate through the list of hashes and query `SELECT * FROM transactions WHERE hash = one_of_the_hash_from_the_list;` to get the detailed transaction data.  
+
+### `ledger_hashes`
 ```
-SELECT * FROM transactions WHERE ledger_sequence = s;
+CREATE TABLE clio.ledger_hashes (
+	hash blob PRIMARY KEY,  # Hash of entire ledger version's data
+	sequence bigint         # The sequence of the ledger version
+) ...
+ ```
+This table stores the hash of all ledger versions by their sequences. 
+### `ledger_range`
 ```
-Cassandra doesn't handle queries like this well, since `ledger_sequence` is not
-the primary key, so we use a second table that maps a ledger sequence number
-to all of the hashes in that ledger:
+CREATE TABLE clio.ledger_range (
+	is_latest boolean PRIMARY KEY,  # Whether this sequence is the stopping range
+	sequence bigint                 # The sequence number of the starting/stopping range
+) ...
+ ```
+This table marks the range of ledger versions that is stored on this specific Cassandra node. Because of its nature, there are only two records in this table with `false` and `true` values for `is_latest`, marking the starting and ending sequence of the ledger range. 
 
+### `objects`
 ```
-CREATE TABLE transaction_hashes (
-ledger_sequence int,
-hash blob,
-PRIMARY KEY(ledger_sequence, blob))
+CREATE TABLE clio.objects (
+	key blob,         # Object index of the object
+	sequence bigint,  # The sequence this object was last updated
+	object blob,      # Data of the object
+	PRIMARY KEY (key, sequence)
+) WITH CLUSTERING ORDER BY (sequence DESC) ...
+ ```
+This table stores the specific data of all objects that ever existed on the XRP network, even if they are deleted (which is represented with a special `0x` value). The records are ordered by descending sequence, where the newest validated ledger objects are at the top. 
+
+This table is updated when all data for a given ledger sequence has been written to the various tables in the database. For each ledger, many associated records are written to different tables. This table is used as a synchronization mechanism, to prevent the application from reading data from a ledger for which all data has not yet been fully written.
+
+### `ledgers`
 ```
-This table uses a compound primary key, so we can have multiple records with
-the same ledger sequence but different hash. Looking up all of the transactions
-in a given ledger then requires querying the transaction_hashes table to get the hashes of
-all of the transactions in the ledger, and then using those hashes to query the
-transactions table. Sometimes we only want the hashes though.
-
-## Ledger data
-
-Ledger data is more complicated than transaction data. Objects have different versions,
-where applying transactions in a particular ledger changes an object with a given
-key. A basic example is an account root object: the balance changes with every
-transaction sent or received, though the key (object ID) for this object remains the same.
-
-Ledger data then is modeled like so:
+CREATE TABLE clio.ledgers (
+	sequence bigint PRIMARY KEY,  # Sequence of the ledger version
+	header blob                   # Data of the header
+) ...
+ ```
+This table stores the ledger header data of specific ledger versions by their sequence.
 
+### `diff`
 ```
-CREATE TABLE objects (
-id blob,
-ledger_sequence int,
-object blob,
-PRIMARY KEY(key,ledger_sequence))
+CREATE TABLE clio.diff (
+	seq bigint,  # Sequence of the ledger version
+	key blob,    # Hash of changes in the ledger version
+	PRIMARY KEY (seq, key)
+) WITH CLUSTERING ORDER BY (key ASC) ...
+ ```
+This table stores the object index of all the changes in each ledger version.
+
+### `account_tx`
 ```
+CREATE TABLE clio.account_tx (
+	account blob,
+	seq_idx frozen<tuple<bigint, bigint>>,  # Tuple of (ledger_index, transaction_index)
+	hash blob,                              # Hash of the transaction
+	PRIMARY KEY (account, seq_idx)
+) WITH CLUSTERING ORDER BY (seq_idx DESC) ...
+ ```
+This table stores the list of transactions affecting a given account. This includes transactions made by the account, as well as transactions received.
 
-The `objects` table has a compound primary key. This is essential. Looking up
-a ledger object as of a given ledger then is just:
+
+### `successor`
 ```
-SELECT object FROM objects WHERE id = ? and ledger_sequence <= ?
-    ORDER BY ledger_sequence DESC LIMIT 1;
-```
-This gives us the most recent ledger object written at or before a specified ledger.
+CREATE TABLE clio.successor (
+	key blob,    # Object index
+	seq bigint,  # The sequnce that this ledger object's predecessor and successor was updated
+	next blob,   # Index of the next object that existed in this sequence
+	PRIMARY KEY (key, seq)
+) WITH CLUSTERING ORDER BY (seq ASC) ...
+  ```
+This table is the important backbone of how histories of ledger objects are stored in Cassandra. The successor table stores the object index of all ledger objects that were validated on the XRP network along with the ledger sequence that the object was upated on. Due to the unique nature of the table with each key being ordered by the sequence, by tracing through the table with a specific sequence number, Clio can recreate a Linked List data structure that represents all the existing ledger object at that ledger sequence. The special value of `0x00...00` and `0xFF...FF` are used to label the head and tail of the Linked List in the successor table. The diagram below showcases how tracing through the same table but with different sequence parameter filtering can result in different Linked List data representing the corresponding past state of the ledger objects. A query like `SELECT * FROM successor WHERE key = ? AND seq <= n ORDER BY seq DESC LIMIT 1;` can effectively trace through the successor table and get the Linked List of a specific sequence `n`.
 
-When a ledger object is deleted, we write a record where `object` is just an empty blob.
+![Successor Table Trace Diagram](https://raw.githubusercontent.com/Shoukozumi/clio/9b2ea3efb6b164b02e9a5f0ef6717065a70f078c/src/backend/README.png)
+*P.S.: The `diff` is `(DELETE 0x00...02, CREATE 0x00...03)` for `seq=1001` and `(CREATE 0x00...04)` for `seq=1002`, which is both accurately reflected with the Linked List trace*
 
-### Next
-Generally RPCs that read ledger data will just use the above query pattern. However,
-a few RPCs (`book_offers` and `ledger_data`) make use of a certain tree operation
-called `successor`, which takes in an object id and ledger sequence, and returns
-the id of the successor object in the ledger. This is the object in the ledger with the smallest id
-greater than the input id.
-
-This problem is quite difficult for clio's data model, since computing this
-generally requires the inner nodes of the tree, which clio doesn't store. A naive
-way to do this with PostgreSQL is like so:
-```
-SELECT * FROM objects WHERE id > ? AND ledger_sequence <= s ORDER BY id ASC, ledger_sequence DESC LIMIT 1;
-```
-This query is not really possible with Cassandra, unless you use ALLOW FILTERING, which
-is an anti pattern (for good reason!). It would require contacting basically every node
-in the entire cluster.
-
-But even with Postgres, this query is not scalable. Why? Consider what the query
-is doing at the database level. The database starts at the input id, and begins scanning
-the table in ascending order of id. It needs to skip over any records that don't actually
-exist in the desired ledger, which are objects that have been deleted, or objects that
-were created later. As ledger history grows, this query skips over more and more records,
-which results in the query taking longer and longer. The time this query takes grows
-unbounded then, as ledger history just keeps growing. With under a million ledgers, this
-query is usable, but as we approach 10 million ledgers are more, the query starts to become very slow.
-
-To alleviate this issue, the data model uses a checkpointing method. We create a second
-table called keys, like so:
-```
-CREATE TABLE keys (
-ledger_sequence int,
-id blob,
-PRIMARY KEY(ledger_sequence, id)
-)
-```
-However, this table does not have an entry for every ledger sequence. Instead,
-this table has an entry for rougly every 1 million ledgers. We call these ledgers
-flag ledgers. For each flag ledger, the keys table contains every object id in that
-ledger, as well as every object id that existed in any ledger between the last flag
-ledger and this one. This is a lot of keys, but not every key that ever existed (which
-is what the naive attempt at implementing successor was iterating over). In this manner,
-the performance is bounded. If we wanted to increase the performance of the successor operation,
-we can increase the frequency of flag ledgers. However, this will use more space. 1 million
-was chosen as a reasonable tradeoff to bound the performance, but not use too much space,
-especially since this is only needed for two RPC calls.
-
-We write to this table every ledger, for each new key. However, we also need to handle
-keys that existed in the previous flag ledger. To do that, at each flag ledger, we
-iterate through the previous flag ledger, and write any keys that are still present
-in the new flag ledger. This is done asynchronously.
-
-## Account Transactions
-rippled offers a RPC called `account_tx`. This RPC returns all transactions that
-affect a given account, and allows users to page backwards or forwards in time.
-Generally, this is a modeled with a table like so:
-```
-CREATE TABLE account_tx (
-account blob,
-ledger_sequence int,
-transaction_index int,
-hash blob,
-PRIMARY KEY(account,ledger_sequence,transaction_index))
-```
-
-An example of looking up from this table going backwards in time is:
-```
-SELECT hash FROM account_tx WHERE account = ? 
-    AND ledger_sequence <= ? and transaction_index <= ? 
-    ORDER BY ledger_sequence DESC, transaction_index DESC;
-```
-
-This query returns the hashes, and then we use those hashes to read from the 
-transactions table.
-
-## Comments
-There are various nuances around how these data models are tuned and optimized
-for each database implementation. Cassandra and PostgreSQL are very different,
-so some slight modifications are needed. However, the general model outlined here
-is implemented by both databases, and when adding a new database, this general model
-should be followed, unless there is a good reason not to. Generally, a database will be
-decently similar to either PostgreSQL or Cassandra, so using those as a basis should
-be sufficient.
-
-Whatever database is used, clio requires strong consistency, and durability. For this
-reason, any replication strategy needs to maintain strong consistency.
+In each new ledger version with sequence `n`, a ledger object `v` can either be **created**, **modified**, or **deleted**. For all three of these operations, the procedure to update the successor table can be broken down in to two steps: 
+ 1. Trace through the Linked List of the previous sequence to to find the ledger object `e` with the greatest object index smaller or equal than the `v`'s index. Save `e`'s `next` value (the index of the next ledger object) as `w`.
+ 2. If `v` is...
+	 1. Being **created**, add two new records of `seq=n` with one being `e` pointing to `v`, and `v` pointing to `w` (Linked List insertion operation).
+	 2. Being **modified**, do nothing.
+	 3. Being **deleted**, add a record of `seq=n` with `e` pointing to `v`'s `next` value (Linked List deletion operation).

src/backend/SimpleCache.cpp

@@ -1,5 +1,6 @@
 #include <backend/SimpleCache.h>
 namespace Backend {
+
 uint32_t
 SimpleCache::latestLedgerSequence() const
 {
@@ -13,6 +14,9 @@ SimpleCache::update(
     uint32_t seq,
     bool isBackground)
 {
+    if (disabled_)
+        return;
+
     {
         std::unique_lock lck{mtx_};
         if (seq > latestSeq_)
@@ -26,6 +30,7 @@ SimpleCache::update(
             {
                 if (isBackground && deletes_.count(obj.key))
                     continue;
+
                 auto& e = map_[obj.key];
                 if (seq > e.seq)
                 {
@@ -41,19 +46,23 @@ SimpleCache::update(
         }
     }
 }
+
 std::optional<LedgerObject>
 SimpleCache::getSuccessor(ripple::uint256 const& key, uint32_t seq) const
 {
     if (!full_)
         return {};
     std::shared_lock{mtx_};
+    successorReqCounter_++;
     if (seq != latestSeq_)
         return {};
     auto e = map_.upper_bound(key);
     if (e == map_.end())
         return {};
+    successorHitCounter_++;
     return {{e->first, e->second.blob}};
 }
+
 std::optional<LedgerObject>
 SimpleCache::getPredecessor(ripple::uint256 const& key, uint32_t seq) const
 {
@@ -74,17 +83,28 @@ SimpleCache::get(ripple::uint256 const& key, uint32_t seq) const
     if (seq > latestSeq_)
         return {};
     std::shared_lock lck{mtx_};
+    objectReqCounter_++;
     auto e = map_.find(key);
     if (e == map_.end())
         return {};
     if (seq < e->second.seq)
         return {};
+    objectHitCounter_++;
     return {e->second.blob};
 }
 
+void
+SimpleCache::setDisabled()
+{
+    disabled_ = true;
+}
+
 void
 SimpleCache::setFull()
 {
+    if (disabled_)
+        return;
+
     full_ = true;
     std::unique_lock lck{mtx_};
     deletes_.clear();
@@ -101,4 +121,18 @@ SimpleCache::size() const
     std::shared_lock lck{mtx_};
     return map_.size();
 }
+float
+SimpleCache::getObjectHitRate() const
+{
+    if (!objectReqCounter_)
+        return 1;
+    return ((float)objectHitCounter_) / objectReqCounter_;
+}
+float
+SimpleCache::getSuccessorHitRate() const
+{
+    if (!successorReqCounter_)
+        return 1;
+    return ((float)successorHitCounter_) / successorReqCounter_;
+}
 }  // namespace Backend

src/backend/SimpleCache.h

@@ -17,10 +17,19 @@ class SimpleCache
         uint32_t seq = 0;
         Blob blob;
     };
+
+    // counters for fetchLedgerObject(s) hit rate
+    mutable std::atomic_uint32_t objectReqCounter_;
+    mutable std::atomic_uint32_t objectHitCounter_;
+    // counters for fetchSuccessorKey hit rate
+    mutable std::atomic_uint32_t successorReqCounter_;
+    mutable std::atomic_uint32_t successorHitCounter_;
+
     std::map<ripple::uint256, CacheEntry> map_;
     mutable std::shared_mutex mtx_;
     uint32_t latestSeq_ = 0;
     std::atomic_bool full_ = false;
+    std::atomic_bool disabled_ = false;
     // temporary set to prevent background thread from writing already deleted
     // data. not used when cache is full
     std::unordered_set<ripple::uint256, ripple::hardened_hash<>> deletes_;
@@ -45,6 +54,9 @@ public:
     std::optional<LedgerObject>
     getPredecessor(ripple::uint256 const& key, uint32_t seq) const;
 
+    void
+    setDisabled();
+
     void
     setFull();
 
@@ -57,6 +69,12 @@ public:
 
     size_t
     size() const;
+
+    float
+    getObjectHitRate() const;
+
+    float
+    getSuccessorHitRate() const;
 };
 
 }  // namespace Backend

src/backend/Types.h

@@ -1,6 +1,7 @@
 #ifndef CLIO_TYPES_H_INCLUDED
 #define CLIO_TYPES_H_INCLUDED
 #include <ripple/basics/base_uint.h>
+#include <ripple/protocol/AccountID.h>
 #include <optional>
 #include <string>
 #include <vector>
@@ -46,16 +47,34 @@ struct TransactionAndMetadata
     }
 };
 
-struct AccountTransactionsCursor
+struct TransactionsCursor
 {
     std::uint32_t ledgerSequence;
     std::uint32_t transactionIndex;
 };
 
-struct AccountTransactions
+struct TransactionsAndCursor
 {
     std::vector<TransactionAndMetadata> txns;
-    std::optional<AccountTransactionsCursor> cursor;
+    std::optional<TransactionsCursor> cursor;
+};
+
+struct NFT
+{
+    ripple::uint256 tokenID;
+    std::uint32_t ledgerSequence;
+    ripple::AccountID owner;
+    bool isBurned;
+
+    // clearly two tokens are the same if they have the same ID, but this
+    // struct stores the state of a given token at a given ledger sequence, so
+    // we also need to compare with ledgerSequence
+    bool
+    operator==(NFT const& other) const
+    {
+        return tokenID == other.tokenID &&
+            ledgerSequence == other.ledgerSequence;
+    }
 };
 
 struct LedgerRange

src/etl/ETLHelpers.h

@@ -23,8 +23,6 @@ class NetworkValidatedLedgers
 
     std::condition_variable cv_;
 
-    bool stopping_ = false;
-
 public:
     static std::shared_ptr<NetworkValidatedLedgers>
     make_ValidatedLedgers()
@@ -174,4 +172,4 @@ getMarkers(size_t numMarkers)
     return markers;
 }
 
-#endif  // RIPPLE_APP_REPORTING_ETLHELPERS_H_INCLUDED
+#endif  // RIPPLE_APP_REPORTING_ETLHELPERS_H_INCLUDED

src/etl/ETLSource.cpp

@@ -8,59 +8,91 @@
 #include <boost/log/trivial.hpp>
 #include <backend/DBHelpers.h>
 #include <etl/ETLSource.h>
+#include <etl/ProbingETLSource.h>
 #include <etl/ReportingETL.h>
+#include <rpc/RPCHelpers.h>
 #include <thread>
 
-// Create ETL source without grpc endpoint
-// Fetch ledger and load initial ledger will fail for this source
-// Primarly used in read-only mode, to monitor when ledgers are validated
-template <class Derived>
-ETLSourceImpl<Derived>::ETLSourceImpl(
-    boost::json::object const& config,
-    boost::asio::io_context& ioContext,
-    std::shared_ptr<BackendInterface> backend,
-    std::shared_ptr<SubscriptionManager> subscriptions,
-    std::shared_ptr<NetworkValidatedLedgers> networkValidatedLedgers,
-    ETLLoadBalancer& balancer)
-    : resolver_(boost::asio::make_strand(ioContext))
-    , networkValidatedLedgers_(networkValidatedLedgers)
-    , backend_(backend)
-    , subscriptions_(subscriptions)
-    , balancer_(balancer)
-    , ioc_(ioContext)
-    , timer_(ioContext)
+void
+ForwardCache::freshen()
 {
-    if (config.contains("ip"))
+    BOOST_LOG_TRIVIAL(trace) << "Freshening ForwardCache";
+
+    auto numOutstanding =
+        std::make_shared<std::atomic_uint>(latestForwarded_.size());
+
+    for (auto const& cacheEntry : latestForwarded_)
     {
-        auto ipJs = config.at("ip").as_string();
-        ip_ = {ipJs.c_str(), ipJs.size()};
+        boost::asio::spawn(
+            strand_,
+            [this, numOutstanding, command = cacheEntry.first](
+                boost::asio::yield_context yield) {
+                boost::json::object request = {{"command", command}};
+                auto resp = source_.requestFromRippled(request, {}, yield);
+
+                if (!resp || resp->contains("error"))
+                    resp = {};
+
+                {
+                    std::unique_lock lk(mtx_);
+                    latestForwarded_[command] = resp;
+                }
+            });
     }
-    if (config.contains("ws_port"))
+}
+
+void
+ForwardCache::clear()
+{
+    std::unique_lock lk(mtx_);
+    for (auto& cacheEntry : latestForwarded_)
+        latestForwarded_[cacheEntry.first] = {};
+}
+
+std::optional<boost::json::object>
+ForwardCache::get(boost::json::object const& request) const
+{
+    std::optional<std::string> command = {};
+    if (request.contains("command") && !request.contains("method") &&
+        request.at("command").is_string())
+        command = request.at("command").as_string().c_str();
+    else if (
+        request.contains("method") && !request.contains("command") &&
+        request.at("method").is_string())
+        command = request.at("method").as_string().c_str();
+
+    if (!command)
+        return {};
+    if (RPC::specifiesCurrentOrClosedLedger(request))
+        return {};
+
+    std::shared_lock lk(mtx_);
+    if (!latestForwarded_.contains(*command))
+        return {};
+
+    return {latestForwarded_.at(*command)};
+}
+
+static boost::beast::websocket::stream_base::timeout
+make_TimeoutOption()
+{
+    // See #289 for details.
+    // TODO: investigate the issue and find if there is a solution other than
+    // introducing artificial timeouts.
+    if (true)
     {
-        auto portjs = config.at("ws_port").as_string();
-        wsPort_ = {portjs.c_str(), portjs.size()};
+        // The only difference between this and the suggested client role is
+        // that idle_timeout is set to 20 instead of none()
+        auto opt = boost::beast::websocket::stream_base::timeout{};
+        opt.handshake_timeout = std::chrono::seconds(30);
+        opt.idle_timeout = std::chrono::seconds(20);
+        opt.keep_alive_pings = false;
+        return opt;
     }
-    if (config.contains("grpc_port"))
+    else
     {
-        auto portjs = config.at("grpc_port").as_string();
-        grpcPort_ = {portjs.c_str(), portjs.size()};
-        try
-        {
-            boost::asio::ip::tcp::endpoint endpoint{
-                boost::asio::ip::make_address(ip_), std::stoi(grpcPort_)};
-            std::stringstream ss;
-            ss << endpoint;
-            stub_ = org::xrpl::rpc::v1::XRPLedgerAPIService::NewStub(
-                grpc::CreateChannel(
-                    ss.str(), grpc::InsecureChannelCredentials()));
-            BOOST_LOG_TRIVIAL(debug) << "Made stub for remote = " << toString();
-        }
-        catch (std::exception const& e)
-        {
-            BOOST_LOG_TRIVIAL(debug)
-                << "Exception while creating stub = " << e.what()
-                << " . Remote = " << toString();
-        }
+        return boost::beast::websocket::stream_base::timeout::suggested(
+            boost::beast::role_type::client);
     }
 }
 
@@ -68,6 +100,12 @@ template <class Derived>
 void
 ETLSourceImpl<Derived>::reconnect(boost::beast::error_code ec)
 {
+    if (paused_)
+        return;
+
+    if (connected_)
+        hooks_.onDisconnected(ec);
+
     connected_ = false;
     // These are somewhat normal errors. operation_aborted occurs on shutdown,
     // when the timer is cancelled. connection_refused will occur repeatedly
@@ -136,11 +174,21 @@ PlainETLSource::close(bool startAgain)
                     }
                     closing_ = false;
                     if (startAgain)
+                    {
+                        ws_ = std::make_unique<boost::beast::websocket::stream<
+                            boost::beast::tcp_stream>>(
+                            boost::asio::make_strand(ioc_));
+
                         run();
+                    }
                 });
         }
         else if (startAgain)
         {
+            ws_ = std::make_unique<
+                boost::beast::websocket::stream<boost::beast::tcp_stream>>(
+                boost::asio::make_strand(ioc_));
+
             run();
         }
     });
@@ -235,21 +283,17 @@ PlainETLSource::onConnect(
         // own timeout system
         boost::beast::get_lowest_layer(derived().ws()).expires_never();
 
-        // Set suggested timeout settings for the websocket
-        derived().ws().set_option(
-            boost::beast::websocket::stream_base::timeout::suggested(
-                boost::beast::role_type::client));
+        // Set a desired timeout for the websocket stream
+        derived().ws().set_option(make_TimeoutOption());
 
         // Set a decorator to change the User-Agent of the handshake
         derived().ws().set_option(
             boost::beast::websocket::stream_base::decorator(
                 [](boost::beast::websocket::request_type& req) {
                     req.set(
-                        boost::beast::http::field::user_agent,
-                        std::string(BOOST_BEAST_VERSION_STRING) +
-                            " clio-client");
+                        boost::beast::http::field::user_agent, "clio-client");
 
-                    req.set("X-User", "coro-client");
+                    req.set("X-User", "clio-client");
                 }));
 
         // Update the host_ string. This will provide the value of the
@@ -281,21 +325,17 @@ SslETLSource::onConnect(
         // own timeout system
         boost::beast::get_lowest_layer(derived().ws()).expires_never();
 
-        // Set suggested timeout settings for the websocket
-        derived().ws().set_option(
-            boost::beast::websocket::stream_base::timeout::suggested(
-                boost::beast::role_type::client));
+        // Set a desired timeout for the websocket stream
+        derived().ws().set_option(make_TimeoutOption());
 
         // Set a decorator to change the User-Agent of the handshake
         derived().ws().set_option(
             boost::beast::websocket::stream_base::decorator(
                 [](boost::beast::websocket::request_type& req) {
                     req.set(
-                        boost::beast::http::field::user_agent,
-                        std::string(BOOST_BEAST_VERSION_STRING) +
-                            " clio-client");
+                        boost::beast::http::field::user_agent, "clio-client");
 
-                    req.set("X-User", "coro-client");
+                    req.set("X-User", "clio-client");
                 }));
 
         // Update the host_ string. This will provide the value of the
@@ -333,6 +373,10 @@ ETLSourceImpl<Derived>::onHandshake(boost::beast::error_code ec)
 {
     BOOST_LOG_TRIVIAL(trace)
         << __func__ << " : ec = " << ec << " - " << toString();
+    if (auto action = hooks_.onConnected(ec);
+        action == ETLSourceHooks::Action::STOP)
+        return;
+
     if (ec)
     {
         // start over
@@ -475,6 +519,7 @@ ETLSourceImpl<Derived>::handleMessage()
             {
                 if (response.contains("transaction"))
                 {
+                    forwardCache_.freshen();
                     subscriptions_->forwardProposedTransaction(response);
                 }
                 else if (
@@ -863,8 +908,6 @@ ETLSourceImpl<Derived>::fetchLedger(
                "correctly on the ETL source. source = "
             << toString() << " status = " << status.error_message();
     }
-    // BOOST_LOG_TRIVIAL(debug)
-    //    << __func__ << " Message size = " << response.ByteSizeLong();
     return {status, std::move(response)};
 }
 
@@ -872,34 +915,18 @@ static std::unique_ptr<ETLSource>
 make_ETLSource(
     boost::json::object const& config,
     boost::asio::io_context& ioContext,
-    std::optional<std::reference_wrapper<boost::asio::ssl::context>> sslCtx,
     std::shared_ptr<BackendInterface> backend,
     std::shared_ptr<SubscriptionManager> subscriptions,
     std::shared_ptr<NetworkValidatedLedgers> networkValidatedLedgers,
     ETLLoadBalancer& balancer)
 {
-    std::unique_ptr<ETLSource> src = nullptr;
-    if (sslCtx)
-    {
-        src = std::make_unique<SslETLSource>(
-            config,
-            ioContext,
-            sslCtx,
-            backend,
-            subscriptions,
-            networkValidatedLedgers,
-            balancer);
-    }
-    else
-    {
-        src = std::make_unique<PlainETLSource>(
-            config,
-            ioContext,
-            backend,
-            subscriptions,
-            networkValidatedLedgers,
-            balancer);
-    }
+    auto src = std::make_unique<ProbingETLSource>(
+        config,
+        ioContext,
+        backend,
+        subscriptions,
+        networkValidatedLedgers,
+        balancer);
 
     src->run();
 
@@ -909,7 +936,6 @@ make_ETLSource(
 ETLLoadBalancer::ETLLoadBalancer(
     boost::json::object const& config,
     boost::asio::io_context& ioContext,
-    std::optional<std::reference_wrapper<boost::asio::ssl::context>> sslCtx,
     std::shared_ptr<BackendInterface> backend,
     std::shared_ptr<SubscriptionManager> subscriptions,
     std::shared_ptr<NetworkValidatedLedgers> nwvl)
@@ -928,13 +954,7 @@ ETLLoadBalancer::ETLLoadBalancer(
     for (auto& entry : config.at("etl_sources").as_array())
     {
         std::unique_ptr<ETLSource> source = make_ETLSource(
-            entry.as_object(),
-            ioContext,
-            sslCtx,
-            backend,
-            subscriptions,
-            nwvl,
-            *this);
+            entry.as_object(), ioContext, backend, subscriptions, nwvl, *this);
 
         sources_.push_back(std::move(source));
         BOOST_LOG_TRIVIAL(info) << __func__ << " : added etl source - "
@@ -973,7 +993,7 @@ ETLLoadBalancer::fetchLedger(
             auto [status, data] = source->fetchLedger(
                 ledgerSequence, getObjects, getObjectNeighbors);
             response = std::move(data);
-            if (status.ok() && (response.validated() || true))
+            if (status.ok() && response.validated())
             {
                 BOOST_LOG_TRIVIAL(info)
                     << "Successfully fetched ledger = " << ledgerSequence
@@ -1026,7 +1046,23 @@ ETLSourceImpl<Derived>::forwardToRippled(
     std::string const& clientIp,
     boost::asio::yield_context& yield) const
 {
-    BOOST_LOG_TRIVIAL(debug) << "Attempting to forward request to tx. "
+    if (auto resp = forwardCache_.get(request); resp)
+    {
+        BOOST_LOG_TRIVIAL(debug) << "request hit forwardCache";
+        return resp;
+    }
+
+    return requestFromRippled(request, clientIp, yield);
+}
+
+template <class Derived>
+std::optional<boost::json::object>
+ETLSourceImpl<Derived>::requestFromRippled(
+    boost::json::object const& request,
+    std::string const& clientIp,
+    boost::asio::yield_context& yield) const
+{
+    BOOST_LOG_TRIVIAL(trace) << "Attempting to forward request to tx. "
                              << "request = " << boost::json::serialize(request);
 
     boost::json::object response;
@@ -1047,7 +1083,7 @@ ETLSourceImpl<Derived>::forwardToRippled(
         // These objects perform our I/O
         tcp::resolver resolver{ioc_};
 
-        BOOST_LOG_TRIVIAL(debug) << "Creating websocket";
+        BOOST_LOG_TRIVIAL(trace) << "Creating websocket";
         auto ws = std::make_unique<websocket::stream<beast::tcp_stream>>(ioc_);
 
         // Look up the domain name
@@ -1057,7 +1093,7 @@ ETLSourceImpl<Derived>::forwardToRippled(
 
         ws->next_layer().expires_after(std::chrono::seconds(3));
 
-        BOOST_LOG_TRIVIAL(debug) << "Connecting websocket";
+        BOOST_LOG_TRIVIAL(trace) << "Connecting websocket";
         // Make the connection on the IP address we get from a lookup
         ws->next_layer().async_connect(results, yield[ec]);
         if (ec)
@@ -1076,15 +1112,15 @@ ETLSourceImpl<Derived>::forwardToRippled(
                         " websocket-client-coro");
                 req.set(http::field::forwarded, "for=" + clientIp);
             }));
-        BOOST_LOG_TRIVIAL(debug) << "client ip: " << clientIp;
+        BOOST_LOG_TRIVIAL(trace) << "client ip: " << clientIp;
 
-        BOOST_LOG_TRIVIAL(debug) << "Performing websocket handshake";
+        BOOST_LOG_TRIVIAL(trace) << "Performing websocket handshake";
         // Perform the websocket handshake
         ws->async_handshake(ip_, "/", yield[ec]);
         if (ec)
             return {};
 
-        BOOST_LOG_TRIVIAL(debug) << "Sending request";
+        BOOST_LOG_TRIVIAL(trace) << "Sending request";
         // Send the message
         ws->async_write(
             net::buffer(boost::json::serialize(request)), yield[ec]);
@@ -1106,7 +1142,7 @@ ETLSourceImpl<Derived>::forwardToRippled(
                 << "Error parsing response: " << std::string{begin, end};
             return {};
         }
-        BOOST_LOG_TRIVIAL(debug) << "Successfully forward request";
+        BOOST_LOG_TRIVIAL(trace) << "Successfully forward request";
 
         response = parsed.as_object();
 

src/etl/ETLSource.h

@@ -15,6 +15,8 @@
 #include <grpcpp/grpcpp.h>
 
 class ETLLoadBalancer;
+class ETLSource;
+class ProbingETLSource;
 class SubscriptionManager;
 
 /// This class manages a connection to a single ETL source. This is almost
@@ -24,6 +26,64 @@ class SubscriptionManager;
 /// has. This class also has methods for extracting said ledgers. Lastly this
 /// class forwards transactions received on the transactions_proposed streams to
 /// any subscribers.
+class ForwardCache
+{
+    using response_type = std::optional<boost::json::object>;
+
+    mutable std::atomic_bool stopping_ = false;
+    mutable std::shared_mutex mtx_;
+    std::unordered_map<std::string, response_type> latestForwarded_;
+
+    boost::asio::io_context::strand strand_;
+    boost::asio::steady_timer timer_;
+    ETLSource const& source_;
+    std::uint32_t duration_ = 10;
+
+    void
+    clear();
+
+public:
+    ForwardCache(
+        boost::json::object const& config,
+        boost::asio::io_context& ioc,
+        ETLSource const& source)
+        : strand_(ioc), timer_(strand_), source_(source)
+    {
+        if (config.contains("cache") && !config.at("cache").is_array())
+            throw std::runtime_error("ETLSource cache must be array");
+
+        if (config.contains("cache_duration") &&
+            !config.at("cache_duration").is_int64())
+            throw std::runtime_error(
+                "ETLSource cache_duration must be a number");
+
+        duration_ = config.contains("cache_duration")
+            ? config.at("cache_duration").as_int64()
+            : 10;
+
+        auto commands = config.contains("cache") ? config.at("cache").as_array()
+                                                 : boost::json::array{};
+
+        for (auto const& command : commands)
+        {
+            if (!command.is_string())
+                throw std::runtime_error(
+                    "ETLSource forward command must be array of strings");
+
+            latestForwarded_[command.as_string().c_str()] = {};
+        }
+    }
+
+    // This is to be called every freshenDuration_ seconds.
+    // It will request information from this etlSource, and
+    // will populate the cache with the latest value. If the
+    // request fails, it will evict that value from the cache.
+    void
+    freshen();
+
+    std::optional<boost::json::object>
+    get(boost::json::object const& command) const;
+};
 
 class ETLSource
 {
@@ -37,6 +97,12 @@ public:
     virtual void
     run() = 0;
 
+    virtual void
+    pause() = 0;
+
+    virtual void
+    resume() = 0;
+
     virtual std::string
     toString() const = 0;
 
@@ -64,6 +130,24 @@ public:
     virtual ~ETLSource()
     {
     }
+
+private:
+    friend ForwardCache;
+    friend ProbingETLSource;
+
+    virtual std::optional<boost::json::object>
+    requestFromRippled(
+        boost::json::object const& request,
+        std::string const& clientIp,
+        boost::asio::yield_context& yield) const = 0;
+};
+
+struct ETLSourceHooks
+{
+    enum class Action { STOP, PROCEED };
+
+    std::function<Action(boost::beast::error_code)> onConnected;
+    std::function<Action(boost::beast::error_code)> onDisconnected;
 };
 
 template <class Derived>
@@ -105,6 +189,14 @@ class ETLSourceImpl : public ETLSource
     std::shared_ptr<SubscriptionManager> subscriptions_;
     ETLLoadBalancer& balancer_;
 
+    ForwardCache forwardCache_;
+
+    std::optional<boost::json::object>
+    requestFromRippled(
+        boost::json::object const& request,
+        std::string const& clientIp,
+        boost::asio::yield_context& yield) const override;
+
 protected:
     Derived&
     derived()
@@ -123,6 +215,10 @@ protected:
 
     std::atomic_bool closing_{false};
 
+    std::atomic_bool paused_{false};
+
+    ETLSourceHooks hooks_;
+
     void
     run() override
     {
@@ -139,7 +235,7 @@ protected:
 public:
     ~ETLSourceImpl()
     {
-        close(false);
+        derived().close(false);
     }
 
     bool
@@ -171,7 +267,54 @@ public:
         std::shared_ptr<BackendInterface> backend,
         std::shared_ptr<SubscriptionManager> subscriptions,
         std::shared_ptr<NetworkValidatedLedgers> networkValidatedLedgers,
-        ETLLoadBalancer& balancer);
+        ETLLoadBalancer& balancer,
+        ETLSourceHooks hooks)
+        : resolver_(boost::asio::make_strand(ioContext))
+        , networkValidatedLedgers_(networkValidatedLedgers)
+        , backend_(backend)
+        , subscriptions_(subscriptions)
+        , balancer_(balancer)
+        , forwardCache_(config, ioContext, *this)
+        , ioc_(ioContext)
+        , timer_(ioContext)
+        , hooks_(hooks)
+    {
+        if (config.contains("ip"))
+        {
+            auto ipJs = config.at("ip").as_string();
+            ip_ = {ipJs.c_str(), ipJs.size()};
+        }
+        if (config.contains("ws_port"))
+        {
+            auto portjs = config.at("ws_port").as_string();
+            wsPort_ = {portjs.c_str(), portjs.size()};
+        }
+        if (config.contains("grpc_port"))
+        {
+            auto portjs = config.at("grpc_port").as_string();
+            grpcPort_ = {portjs.c_str(), portjs.size()};
+            try
+            {
+                boost::asio::ip::tcp::endpoint endpoint{
+                    boost::asio::ip::make_address(ip_), std::stoi(grpcPort_)};
+                std::stringstream ss;
+                ss << endpoint;
+                grpc::ChannelArguments chArgs;
+                chArgs.SetMaxReceiveMessageSize(-1);
+                stub_ = org::xrpl::rpc::v1::XRPLedgerAPIService::NewStub(
+                    grpc::CreateCustomChannel(
+                        ss.str(), grpc::InsecureChannelCredentials(), chArgs));
+                BOOST_LOG_TRIVIAL(debug)
+                    << "Made stub for remote = " << toString();
+            }
+            catch (std::exception const& e)
+            {
+                BOOST_LOG_TRIVIAL(debug)
+                    << "Exception while creating stub = " << e.what()
+                    << " . Remote = " << toString();
+            }
+        }
+    }
 
     /// @param sequence ledger sequence to check for
     /// @return true if this source has the desired ledger
@@ -295,6 +438,22 @@ public:
     void
     reconnect(boost::beast::error_code ec);
 
+    /// Pause the source effectively stopping it from trying to reconnect
+    void
+    pause() override
+    {
+        paused_ = true;
+        derived().close(false);
+    }
+
+    /// Resume the source allowing it to reconnect again
+    void
+    resume() override
+    {
+        paused_ = false;
+        derived().close(true);
+    }
+
     /// Callback
     void
     onResolve(
@@ -344,8 +503,16 @@ public:
         std::shared_ptr<BackendInterface> backend,
         std::shared_ptr<SubscriptionManager> subscriptions,
         std::shared_ptr<NetworkValidatedLedgers> nwvl,
-        ETLLoadBalancer& balancer)
-        : ETLSourceImpl(config, ioc, backend, subscriptions, nwvl, balancer)
+        ETLLoadBalancer& balancer,
+        ETLSourceHooks hooks)
+        : ETLSourceImpl(
+              config,
+              ioc,
+              backend,
+              subscriptions,
+              nwvl,
+              balancer,
+              std::move(hooks))
         , ws_(std::make_unique<
               boost::beast::websocket::stream<boost::beast::tcp_stream>>(
               boost::asio::make_strand(ioc)))
@@ -386,8 +553,16 @@ public:
         std::shared_ptr<BackendInterface> backend,
         std::shared_ptr<SubscriptionManager> subscriptions,
         std::shared_ptr<NetworkValidatedLedgers> nwvl,
-        ETLLoadBalancer& balancer)
-        : ETLSourceImpl(config, ioc, backend, subscriptions, nwvl, balancer)
+        ETLLoadBalancer& balancer,
+        ETLSourceHooks hooks)
+        : ETLSourceImpl(
+              config,
+              ioc,
+              backend,
+              subscriptions,
+              nwvl,
+              balancer,
+              std::move(hooks))
         , sslCtx_(sslCtx)
         , ws_(std::make_unique<boost::beast::websocket::stream<
                   boost::beast::ssl_stream<boost::beast::tcp_stream>>>(
@@ -437,7 +612,6 @@ public:
     ETLLoadBalancer(
         boost::json::object const& config,
         boost::asio::io_context& ioContext,
-        std::optional<std::reference_wrapper<boost::asio::ssl::context>> sslCtx,
         std::shared_ptr<BackendInterface> backend,
         std::shared_ptr<SubscriptionManager> subscriptions,
         std::shared_ptr<NetworkValidatedLedgers> nwvl);
@@ -446,13 +620,12 @@ public:
     make_ETLLoadBalancer(
         boost::json::object const& config,
         boost::asio::io_context& ioc,
-        std::optional<std::reference_wrapper<boost::asio::ssl::context>> sslCtx,
         std::shared_ptr<BackendInterface> backend,
         std::shared_ptr<SubscriptionManager> subscriptions,
         std::shared_ptr<NetworkValidatedLedgers> validatedLedgers)
     {
         return std::make_shared<ETLLoadBalancer>(
-            config, ioc, sslCtx, backend, subscriptions, validatedLedgers);
+            config, ioc, backend, subscriptions, validatedLedgers);
     }
 
     ~ETLLoadBalancer()

src/etl/NFTHelpers.cpp

@@ -0,0 +1,370 @@
+#include <ripple/app/tx/impl/details/NFTokenUtils.h>
+#include <ripple/protocol/STBase.h>
+#include <ripple/protocol/STTx.h>
+#include <ripple/protocol/TxMeta.h>
+#include <vector>
+
+#include <backend/BackendInterface.h>
+#include <backend/DBHelpers.h>
+#include <backend/Types.h>
+
+std::pair<std::vector<NFTTransactionsData>, std::optional<NFTsData>>
+getNFTokenMintData(ripple::TxMeta const& txMeta, ripple::STTx const& sttx)
+{
+    // To find the minted token ID, we put all tokenIDs referenced in the
+    // metadata from prior to the tx application into one vector, then all
+    // tokenIDs referenced in the metadata from after the tx application into
+    // another, then find the one tokenID that was added by this tx
+    // application.
+    std::vector<ripple::uint256> prevIDs;
+    std::vector<ripple::uint256> finalIDs;
+
+    // The owner is not necessarily the issuer, if using authorized minter
+    // flow. Determine owner from the ledger object ID of the NFTokenPages
+    // that were changed.
+    std::optional<ripple::AccountID> owner;
+
+    for (ripple::STObject const& node : txMeta.getNodes())
+    {
+        if (node.getFieldU16(ripple::sfLedgerEntryType) !=
+            ripple::ltNFTOKEN_PAGE)
+            continue;
+
+        if (!owner)
+            owner = ripple::AccountID::fromVoid(
+                node.getFieldH256(ripple::sfLedgerIndex).data());
+
+        if (node.getFName() == ripple::sfCreatedNode)
+        {
+            ripple::STArray const& toAddNFTs =
+                node.peekAtField(ripple::sfNewFields)
+                    .downcast<ripple::STObject>()
+                    .getFieldArray(ripple::sfNFTokens);
+            std::transform(
+                toAddNFTs.begin(),
+                toAddNFTs.end(),
+                std::back_inserter(finalIDs),
+                [](ripple::STObject const& nft) {
+                    return nft.getFieldH256(ripple::sfNFTokenID);
+                });
+        }
+        // Else it's modified, as there should never be a deleted NFToken page
+        // as a result of a mint.
+        else
+        {
+            // When a mint results in splitting an existing page,
+            // it results in a created page and a modified node. Sometimes,
+            // the created node needs to be linked to a third page, resulting
+            // in modifying that third page's PreviousPageMin or NextPageMin
+            // field changing, but no NFTs within that page changing. In this
+            // case, there will be no previous NFTs and we need to skip.
+            // However, there will always be NFTs listed in the final fields,
+            // as rippled outputs all fields in final fields even if they were
+            // not changed.
+            ripple::STObject const& previousFields =
+                node.peekAtField(ripple::sfPreviousFields)
+                    .downcast<ripple::STObject>();
+            if (!previousFields.isFieldPresent(ripple::sfNFTokens))
+                continue;
+
+            ripple::STArray const& toAddNFTs =
+                previousFields.getFieldArray(ripple::sfNFTokens);
+            std::transform(
+                toAddNFTs.begin(),
+                toAddNFTs.end(),
+                std::back_inserter(prevIDs),
+                [](ripple::STObject const& nft) {
+                    return nft.getFieldH256(ripple::sfNFTokenID);
+                });
+
+            ripple::STArray const& toAddFinalNFTs =
+                node.peekAtField(ripple::sfFinalFields)
+                    .downcast<ripple::STObject>()
+                    .getFieldArray(ripple::sfNFTokens);
+            std::transform(
+                toAddFinalNFTs.begin(),
+                toAddFinalNFTs.end(),
+                std::back_inserter(finalIDs),
+                [](ripple::STObject const& nft) {
+                    return nft.getFieldH256(ripple::sfNFTokenID);
+                });
+        }
+    }
+
+    std::sort(finalIDs.begin(), finalIDs.end());
+    std::sort(prevIDs.begin(), prevIDs.end());
+    std::vector<ripple::uint256> tokenIDResult;
+    std::set_difference(
+        finalIDs.begin(),
+        finalIDs.end(),
+        prevIDs.begin(),
+        prevIDs.end(),
+        std::inserter(tokenIDResult, tokenIDResult.begin()));
+    if (tokenIDResult.size() == 1 && owner)
+        return {
+            {NFTTransactionsData(
+                tokenIDResult.front(), txMeta, sttx.getTransactionID())},
+            NFTsData(tokenIDResult.front(), *owner, txMeta, false)};
+
+    std::stringstream msg;
+    msg << __func__ << " - unexpected NFTokenMint data in tx "
+        << sttx.getTransactionID();
+    throw std::runtime_error(msg.str());
+}
+
+std::pair<std::vector<NFTTransactionsData>, std::optional<NFTsData>>
+getNFTokenBurnData(ripple::TxMeta const& txMeta, ripple::STTx const& sttx)
+{
+    ripple::uint256 const tokenID = sttx.getFieldH256(ripple::sfNFTokenID);
+    std::vector<NFTTransactionsData> const txs = {
+        NFTTransactionsData(tokenID, txMeta, sttx.getTransactionID())};
+
+    // Determine who owned the token when it was burned by finding an
+    // NFTokenPage that was deleted or modified that contains this
+    // tokenID.
+    for (ripple::STObject const& node : txMeta.getNodes())
+    {
+        if (node.getFieldU16(ripple::sfLedgerEntryType) !=
+                ripple::ltNFTOKEN_PAGE ||
+            node.getFName() == ripple::sfCreatedNode)
+            continue;
+
+        // NFT burn can result in an NFTokenPage being modified to no longer
+        // include the target, or an NFTokenPage being deleted. If this is
+        // modified, we want to look for the target in the fields prior to
+        // modification. If deleted, it's possible that the page was modified
+        // to remove the target NFT prior to the entire page being deleted. In
+        // this case, we need to look in the PreviousFields. Otherwise, the
+        // page was not modified prior to deleting and we need to look in the
+        // FinalFields.
+        std::optional<ripple::STArray> prevNFTs;
+
+        if (node.isFieldPresent(ripple::sfPreviousFields))
+        {
+            ripple::STObject const& previousFields =
+                node.peekAtField(ripple::sfPreviousFields)
+                    .downcast<ripple::STObject>();
+            if (previousFields.isFieldPresent(ripple::sfNFTokens))
+                prevNFTs = previousFields.getFieldArray(ripple::sfNFTokens);
+        }
+        else if (!prevNFTs && node.getFName() == ripple::sfDeletedNode)
+            prevNFTs = node.peekAtField(ripple::sfFinalFields)
+                           .downcast<ripple::STObject>()
+                           .getFieldArray(ripple::sfNFTokens);
+
+        if (!prevNFTs)
+            continue;
+
+        auto const nft = std::find_if(
+            prevNFTs->begin(),
+            prevNFTs->end(),
+            [&tokenID](ripple::STObject const& candidate) {
+                return candidate.getFieldH256(ripple::sfNFTokenID) == tokenID;
+            });
+        if (nft != prevNFTs->end())
+            return std::make_pair(
+                txs,
+                NFTsData(
+                    tokenID,
+                    ripple::AccountID::fromVoid(
+                        node.getFieldH256(ripple::sfLedgerIndex).data()),
+                    txMeta,
+                    true));
+    }
+
+    std::stringstream msg;
+    msg << __func__ << " - could not determine owner at burntime for tx "
+        << sttx.getTransactionID();
+    throw std::runtime_error(msg.str());
+}
+
+std::pair<std::vector<NFTTransactionsData>, std::optional<NFTsData>>
+getNFTokenAcceptOfferData(
+    ripple::TxMeta const& txMeta,
+    ripple::STTx const& sttx)
+{
+    // If we have the buy offer from this tx, we can determine the owner
+    // more easily by just looking at the owner of the accepted NFTokenOffer
+    // object.
+    if (sttx.isFieldPresent(ripple::sfNFTokenBuyOffer))
+    {
+        auto const affectedBuyOffer = std::find_if(
+            txMeta.getNodes().begin(),
+            txMeta.getNodes().end(),
+            [&sttx](ripple::STObject const& node) {
+                return node.getFieldH256(ripple::sfLedgerIndex) ==
+                    sttx.getFieldH256(ripple::sfNFTokenBuyOffer);
+            });
+        if (affectedBuyOffer == txMeta.getNodes().end())
+        {
+            std::stringstream msg;
+            msg << __func__ << " - unexpected NFTokenAcceptOffer data in tx "
+                << sttx.getTransactionID();
+            throw std::runtime_error(msg.str());
+        }
+
+        ripple::uint256 const tokenID =
+            affectedBuyOffer->peekAtField(ripple::sfFinalFields)
+                .downcast<ripple::STObject>()
+                .getFieldH256(ripple::sfNFTokenID);
+
+        ripple::AccountID const owner =
+            affectedBuyOffer->peekAtField(ripple::sfFinalFields)
+                .downcast<ripple::STObject>()
+                .getAccountID(ripple::sfOwner);
+        return {
+            {NFTTransactionsData(tokenID, txMeta, sttx.getTransactionID())},
+            NFTsData(tokenID, owner, txMeta, false)};
+    }
+
+    // Otherwise we have to infer the new owner from the affected nodes.
+    auto const affectedSellOffer = std::find_if(
+        txMeta.getNodes().begin(),
+        txMeta.getNodes().end(),
+        [&sttx](ripple::STObject const& node) {
+            return node.getFieldH256(ripple::sfLedgerIndex) ==
+                sttx.getFieldH256(ripple::sfNFTokenSellOffer);
+        });
+    if (affectedSellOffer == txMeta.getNodes().end())
+    {
+        std::stringstream msg;
+        msg << __func__ << " - unexpected NFTokenAcceptOffer data in tx "
+            << sttx.getTransactionID();
+        throw std::runtime_error(msg.str());
+    }
+
+    ripple::uint256 const tokenID =
+        affectedSellOffer->peekAtField(ripple::sfFinalFields)
+            .downcast<ripple::STObject>()
+            .getFieldH256(ripple::sfNFTokenID);
+
+    ripple::AccountID const seller =
+        affectedSellOffer->peekAtField(ripple::sfFinalFields)
+            .downcast<ripple::STObject>()
+            .getAccountID(ripple::sfOwner);
+
+    for (ripple::STObject const& node : txMeta.getNodes())
+    {
+        if (node.getFieldU16(ripple::sfLedgerEntryType) !=
+                ripple::ltNFTOKEN_PAGE ||
+            node.getFName() == ripple::sfDeletedNode)
+            continue;
+
+        ripple::AccountID const nodeOwner = ripple::AccountID::fromVoid(
+            node.getFieldH256(ripple::sfLedgerIndex).data());
+        if (nodeOwner == seller)
+            continue;
+
+        ripple::STArray const& nfts = [&node] {
+            if (node.getFName() == ripple::sfCreatedNode)
+                return node.peekAtField(ripple::sfNewFields)
+                    .downcast<ripple::STObject>()
+                    .getFieldArray(ripple::sfNFTokens);
+            return node.peekAtField(ripple::sfFinalFields)
+                .downcast<ripple::STObject>()
+                .getFieldArray(ripple::sfNFTokens);
+        }();
+
+        auto const nft = std::find_if(
+            nfts.begin(),
+            nfts.end(),
+            [&tokenID](ripple::STObject const& candidate) {
+                return candidate.getFieldH256(ripple::sfNFTokenID) == tokenID;
+            });
+        if (nft != nfts.end())
+            return {
+                {NFTTransactionsData(tokenID, txMeta, sttx.getTransactionID())},
+                NFTsData(tokenID, nodeOwner, txMeta, false)};
+    }
+
+    std::stringstream msg;
+    msg << __func__ << " - unexpected NFTokenAcceptOffer data in tx "
+        << sttx.getTransactionID();
+    throw std::runtime_error(msg.str());
+}
+
+// This is the only transaction where there can be more than 1 element in
+// the returned vector, because you can cancel multiple offers in one
+// transaction using this feature. This transaction also never returns an
+// NFTsData because it does not change the state of an NFT itself.
+std::pair<std::vector<NFTTransactionsData>, std::optional<NFTsData>>
+getNFTokenCancelOfferData(
+    ripple::TxMeta const& txMeta,
+    ripple::STTx const& sttx)
+{
+    std::vector<NFTTransactionsData> txs;
+    for (ripple::STObject const& node : txMeta.getNodes())
+    {
+        if (node.getFieldU16(ripple::sfLedgerEntryType) !=
+            ripple::ltNFTOKEN_OFFER)
+            continue;
+
+        ripple::uint256 const tokenID = node.peekAtField(ripple::sfFinalFields)
+                                            .downcast<ripple::STObject>()
+                                            .getFieldH256(ripple::sfNFTokenID);
+        txs.emplace_back(tokenID, txMeta, sttx.getTransactionID());
+    }
+
+    // Deduplicate any transactions based on tokenID/txIdx combo. Can't just
+    // use txIdx because in this case one tx can cancel offers for several
+    // NFTs.
+    std::sort(
+        txs.begin(),
+        txs.end(),
+        [](NFTTransactionsData const& a, NFTTransactionsData const& b) {
+            return a.tokenID < b.tokenID &&
+                a.transactionIndex < b.transactionIndex;
+        });
+    auto last = std::unique(
+        txs.begin(),
+        txs.end(),
+        [](NFTTransactionsData const& a, NFTTransactionsData const& b) {
+            return a.tokenID == b.tokenID &&
+                a.transactionIndex == b.transactionIndex;
+        });
+    txs.erase(last, txs.end());
+    return {txs, {}};
+}
+
+// This transaction never returns an NFTokensData because it does not
+// change the state of an NFT itself.
+std::pair<std::vector<NFTTransactionsData>, std::optional<NFTsData>>
+getNFTokenCreateOfferData(
+    ripple::TxMeta const& txMeta,
+    ripple::STTx const& sttx)
+{
+    return {
+        {NFTTransactionsData(
+            sttx.getFieldH256(ripple::sfNFTokenID),
+            txMeta,
+            sttx.getTransactionID())},
+        {}};
+}
+
+std::pair<std::vector<NFTTransactionsData>, std::optional<NFTsData>>
+getNFTData(ripple::TxMeta const& txMeta, ripple::STTx const& sttx)
+{
+    if (txMeta.getResultTER() != ripple::tesSUCCESS)
+        return {{}, {}};
+
+    switch (sttx.getTxnType())
+    {
+        case ripple::TxType::ttNFTOKEN_MINT:
+            return getNFTokenMintData(txMeta, sttx);
+
+        case ripple::TxType::ttNFTOKEN_BURN:
+            return getNFTokenBurnData(txMeta, sttx);
+
+        case ripple::TxType::ttNFTOKEN_ACCEPT_OFFER:
+            return getNFTokenAcceptOfferData(txMeta, sttx);
+
+        case ripple::TxType::ttNFTOKEN_CANCEL_OFFER:
+            return getNFTokenCancelOfferData(txMeta, sttx);
+
+        case ripple::TxType::ttNFTOKEN_CREATE_OFFER:
+            return getNFTokenCreateOfferData(txMeta, sttx);
+
+        default:
+            return {{}, {}};
+    }
+}

src/etl/ProbingETLSource.cpp

@@ -0,0 +1,190 @@
+#include <etl/ProbingETLSource.h>
+
+ProbingETLSource::ProbingETLSource(
+    boost::json::object const& config,
+    boost::asio::io_context& ioc,
+    std::shared_ptr<BackendInterface> backend,
+    std::shared_ptr<SubscriptionManager> subscriptions,
+    std::shared_ptr<NetworkValidatedLedgers> nwvl,
+    ETLLoadBalancer& balancer,
+    boost::asio::ssl::context sslCtx)
+    : ioc_{ioc}
+    , sslCtx_{std::move(sslCtx)}
+    , sslSrc_{make_shared<SslETLSource>(
+          config,
+          ioc,
+          std::ref(sslCtx_),
+          backend,
+          subscriptions,
+          nwvl,
+          balancer,
+          make_SSLHooks())}
+    , plainSrc_{make_shared<PlainETLSource>(
+          config,
+          ioc,
+          backend,
+          subscriptions,
+          nwvl,
+          balancer,
+          make_PlainHooks())}
+{
+}
+
+void
+ProbingETLSource::run()
+{
+    sslSrc_->run();
+    plainSrc_->run();
+}
+
+void
+ProbingETLSource::pause()
+{
+    sslSrc_->pause();
+    plainSrc_->pause();
+}
+
+void
+ProbingETLSource::resume()
+{
+    sslSrc_->resume();
+    plainSrc_->resume();
+}
+
+bool
+ProbingETLSource::isConnected() const
+{
+    return currentSrc_ && currentSrc_->isConnected();
+}
+
+bool
+ProbingETLSource::hasLedger(uint32_t sequence) const
+{
+    if (!currentSrc_)
+        return false;
+    return currentSrc_->hasLedger(sequence);
+}
+
+boost::json::object
+ProbingETLSource::toJson() const
+{
+    if (!currentSrc_)
+        return {};
+    return currentSrc_->toJson();
+}
+
+std::string
+ProbingETLSource::toString() const
+{
+    if (!currentSrc_)
+        return "{ probing }";
+    return currentSrc_->toString();
+}
+
+bool
+ProbingETLSource::loadInitialLedger(
+    std::uint32_t ledgerSequence,
+    std::uint32_t numMarkers,
+    bool cacheOnly)
+{
+    if (!currentSrc_)
+        return false;
+    return currentSrc_->loadInitialLedger(
+        ledgerSequence, numMarkers, cacheOnly);
+}
+
+std::pair<grpc::Status, org::xrpl::rpc::v1::GetLedgerResponse>
+ProbingETLSource::fetchLedger(
+    uint32_t ledgerSequence,
+    bool getObjects,
+    bool getObjectNeighbors)
+{
+    if (!currentSrc_)
+        return {};
+    return currentSrc_->fetchLedger(
+        ledgerSequence, getObjects, getObjectNeighbors);
+}
+
+std::optional<boost::json::object>
+ProbingETLSource::forwardToRippled(
+    boost::json::object const& request,
+    std::string const& clientIp,
+    boost::asio::yield_context& yield) const
+{
+    if (!currentSrc_)
+        return {};
+    return currentSrc_->forwardToRippled(request, clientIp, yield);
+}
+
+std::optional<boost::json::object>
+ProbingETLSource::requestFromRippled(
+    boost::json::object const& request,
+    std::string const& clientIp,
+    boost::asio::yield_context& yield) const
+{
+    if (!currentSrc_)
+        return {};
+    return currentSrc_->requestFromRippled(request, clientIp, yield);
+}
+
+ETLSourceHooks
+ProbingETLSource::make_SSLHooks() noexcept
+{
+    return {// onConnected
+            [this](auto ec) {
+                std::lock_guard lck(mtx_);
+                if (currentSrc_)
+                    return ETLSourceHooks::Action::STOP;
+
+                if (!ec)
+                {
+                    plainSrc_->pause();
+                    currentSrc_ = sslSrc_;
+                    BOOST_LOG_TRIVIAL(info)
+                        << "Selected WSS as the main source: "
+                        << currentSrc_->toString();
+                }
+                return ETLSourceHooks::Action::PROCEED;
+            },
+            // onDisconnected
+            [this](auto ec) {
+                std::lock_guard lck(mtx_);
+                if (currentSrc_)
+                {
+                    currentSrc_ = nullptr;
+                    plainSrc_->resume();
+                }
+                return ETLSourceHooks::Action::STOP;
+            }};
+}
+
+ETLSourceHooks
+ProbingETLSource::make_PlainHooks() noexcept
+{
+    return {// onConnected
+            [this](auto ec) {
+                std::lock_guard lck(mtx_);
+                if (currentSrc_)
+                    return ETLSourceHooks::Action::STOP;
+
+                if (!ec)
+                {
+                    sslSrc_->pause();
+                    currentSrc_ = plainSrc_;
+                    BOOST_LOG_TRIVIAL(info)
+                        << "Selected Plain WS as the main source: "
+                        << currentSrc_->toString();
+                }
+                return ETLSourceHooks::Action::PROCEED;
+            },
+            // onDisconnected
+            [this](auto ec) {
+                std::lock_guard lck(mtx_);
+                if (currentSrc_)
+                {
+                    currentSrc_ = nullptr;
+                    sslSrc_->resume();
+                }
+                return ETLSourceHooks::Action::STOP;
+            }};
+}

src/etl/ProbingETLSource.h

@@ -0,0 +1,91 @@
+#ifndef RIPPLE_APP_REPORTING_PROBINGETLSOURCE_H_INCLUDED
+#define RIPPLE_APP_REPORTING_PROBINGETLSOURCE_H_INCLUDED
+
+#include <boost/asio.hpp>
+#include <boost/beast/core.hpp>
+#include <boost/beast/core/string.hpp>
+#include <boost/beast/ssl.hpp>
+#include <boost/beast/websocket.hpp>
+#include <etl/ETLSource.h>
+#include <mutex>
+
+/// This ETLSource implementation attempts to connect over both secure websocket
+/// and plain websocket. First to connect pauses the other and the probing is
+/// considered done at this point. If however the connected source loses
+/// connection the probing is kickstarted again.
+class ProbingETLSource : public ETLSource
+{
+    std::mutex mtx_;
+    boost::asio::io_context& ioc_;
+    boost::asio::ssl::context sslCtx_;
+    std::shared_ptr<ETLSource> sslSrc_;
+    std::shared_ptr<ETLSource> plainSrc_;
+    std::shared_ptr<ETLSource> currentSrc_;
+
+public:
+    ProbingETLSource(
+        boost::json::object const& config,
+        boost::asio::io_context& ioc,
+        std::shared_ptr<BackendInterface> backend,
+        std::shared_ptr<SubscriptionManager> subscriptions,
+        std::shared_ptr<NetworkValidatedLedgers> nwvl,
+        ETLLoadBalancer& balancer,
+        boost::asio::ssl::context sslCtx = boost::asio::ssl::context{
+            boost::asio::ssl::context::tlsv12});
+
+    ~ProbingETLSource() = default;
+
+    void
+    run() override;
+
+    void
+    pause() override;
+
+    void
+    resume() override;
+
+    bool
+    isConnected() const override;
+
+    bool
+    hasLedger(uint32_t sequence) const override;
+
+    boost::json::object
+    toJson() const override;
+
+    std::string
+    toString() const override;
+
+    bool
+    loadInitialLedger(
+        std::uint32_t ledgerSequence,
+        std::uint32_t numMarkers,
+        bool cacheOnly = false) override;
+
+    std::pair<grpc::Status, org::xrpl::rpc::v1::GetLedgerResponse>
+    fetchLedger(
+        uint32_t ledgerSequence,
+        bool getObjects = true,
+        bool getObjectNeighbors = false) override;
+
+    std::optional<boost::json::object>
+    forwardToRippled(
+        boost::json::object const& request,
+        std::string const& clientIp,
+        boost::asio::yield_context& yield) const override;
+
+private:
+    std::optional<boost::json::object>
+    requestFromRippled(
+        boost::json::object const& request,
+        std::string const& clientIp,
+        boost::asio::yield_context& yield) const override;
+
+    ETLSourceHooks
+    make_SSLHooks() noexcept;
+
+    ETLSourceHooks
+    make_PlainHooks() noexcept;
+};
+
+#endif

src/etl/ReportingETL.cpp

@@ -28,12 +28,13 @@ toString(ripple::LedgerInfo const& info)
 }
 }  // namespace detail
 
-std::vector<AccountTransactionsData>
+FormattedTransactionsData
 ReportingETL::insertTransactions(
     ripple::LedgerInfo const& ledger,
     org::xrpl::rpc::v1::GetLedgerResponse& data)
 {
-    std::vector<AccountTransactionsData> accountTxData;
+    FormattedTransactionsData result;
+
     for (auto& txn :
          *(data.mutable_transactions_list()->mutable_transactions()))
     {
@@ -42,21 +43,22 @@ ReportingETL::insertTransactions(
         ripple::SerialIter it{raw->data(), raw->size()};
         ripple::STTx sttx{it};
 
-        auto txSerializer =
-            std::make_shared<ripple::Serializer>(sttx.getSerializer());
-
-        ripple::TxMeta txMeta{
-            sttx.getTransactionID(), ledger.seq, txn.metadata_blob()};
-
-        auto metaSerializer = std::make_shared<ripple::Serializer>(
-            txMeta.getAsObject().getSerializer());
-
         BOOST_LOG_TRIVIAL(trace)
             << __func__ << " : "
             << "Inserting transaction = " << sttx.getTransactionID();
 
+        ripple::TxMeta txMeta{
+            sttx.getTransactionID(), ledger.seq, txn.metadata_blob()};
+
+        auto const [nftTxs, maybeNFT] = getNFTData(txMeta, sttx);
+        result.nfTokenTxData.insert(
+            result.nfTokenTxData.end(), nftTxs.begin(), nftTxs.end());
+        if (maybeNFT)
+            result.nfTokensData.push_back(*maybeNFT);
+
         auto journal = ripple::debugLog();
-        accountTxData.emplace_back(txMeta, sttx.getTransactionID(), journal);
+        result.accountTxData.emplace_back(
+            txMeta, sttx.getTransactionID(), journal);
         std::string keyStr{(const char*)sttx.getTransactionID().data(), 32};
         backend_->writeTransaction(
             std::move(keyStr),
@@ -65,7 +67,27 @@ ReportingETL::insertTransactions(
             std::move(*raw),
             std::move(*txn.mutable_metadata_blob()));
     }
-    return accountTxData;
+
+    // Remove all but the last NFTsData for each id. unique removes all
+    // but the first of a group, so we want to reverse sort by transaction
+    // index
+    std::sort(
+        result.nfTokensData.begin(),
+        result.nfTokensData.end(),
+        [](NFTsData const& a, NFTsData const& b) {
+            return a.tokenID > b.tokenID &&
+                a.transactionIndex > b.transactionIndex;
+        });
+    // Now we can unique the NFTs by tokenID.
+    auto last = std::unique(
+        result.nfTokensData.begin(),
+        result.nfTokensData.end(),
+        [](NFTsData const& a, NFTsData const& b) {
+            return a.tokenID == b.tokenID;
+        });
+    result.nfTokensData.erase(last, result.nfTokensData.end());
+
+    return result;
 }
 
 std::optional<ripple::LedgerInfo>
@@ -106,7 +128,7 @@ ReportingETL::loadInitialLedger(uint32_t startingSequence)
         lgrInfo, std::move(*ledgerData->mutable_ledger_header()));
 
     BOOST_LOG_TRIVIAL(debug) << __func__ << " wrote ledger";
-    std::vector<AccountTransactionsData> accountTxData =
+    FormattedTransactionsData insertTxResult =
         insertTransactions(lgrInfo, *ledgerData);
     BOOST_LOG_TRIVIAL(debug) << __func__ << " inserted txns";
 
@@ -119,8 +141,12 @@ ReportingETL::loadInitialLedger(uint32_t startingSequence)
     BOOST_LOG_TRIVIAL(debug) << __func__ << " loaded initial ledger";
 
     if (!stopping_)
-        backend_->writeAccountTransactions(std::move(accountTxData));
-
+    {
+        backend_->writeAccountTransactions(
+            std::move(insertTxResult.accountTxData));
+        backend_->writeNFTs(std::move(insertTxResult.nfTokensData));
+        backend_->writeNFTTransactions(std::move(insertTxResult.nfTokenTxData));
+    }
     backend_->finishWrites(startingSequence);
 
     auto end = std::chrono::system_clock::now();
@@ -147,11 +173,9 @@ ReportingETL::publishLedger(ripple::LedgerInfo const& lgrInfo)
         backend_->cache().update(diff, lgrInfo.seq);
         backend_->updateRange(lgrInfo.seq);
     }
-    auto now = std::chrono::duration_cast<std::chrono::seconds>(
-                   std::chrono::system_clock::now().time_since_epoch())
-                   .count();
-    auto closeTime = lgrInfo.closeTime.time_since_epoch().count();
-    auto age = now - (rippleEpochStart + closeTime);
+
+    setLastClose(lgrInfo.closeTime);
+    auto age = lastCloseAgeSeconds();
     // if the ledger closed over 10 minutes ago, assume we are still
     // catching up and don't publish
     if (age < 600)
@@ -513,15 +537,15 @@ ReportingETL::buildNextLedger(org::xrpl::rpc::v1::GetLedgerResponse& rawData)
         << __func__ << " : "
         << "Inserted/modified/deleted all objects. Number of objects = "
         << rawData.ledger_objects().objects_size();
-    std::vector<AccountTransactionsData> accountTxData{
-        insertTransactions(lgrInfo, rawData)};
+    FormattedTransactionsData insertTxResult =
+        insertTransactions(lgrInfo, rawData);
     BOOST_LOG_TRIVIAL(debug)
         << __func__ << " : "
         << "Inserted all transactions. Number of transactions  = "
         << rawData.transactions_list().transactions_size();
-
-    backend_->writeAccountTransactions(std::move(accountTxData));
-
+    backend_->writeAccountTransactions(std::move(insertTxResult.accountTxData));
+    backend_->writeNFTs(std::move(insertTxResult.nfTokensData));
+    backend_->writeNFTTransactions(std::move(insertTxResult.nfTokenTxData));
     BOOST_LOG_TRIVIAL(debug) << __func__ << " : "
                              << "wrote account_tx";
     auto start = std::chrono::system_clock::now();
@@ -670,8 +694,6 @@ ReportingETL::runETLPipeline(uint32_t startSequence, int numExtractors)
         beast::setCurrentThreadName("rippled: ReportingETL transform");
         uint32_t currentSequence = startSequence;
 
-        auto begin = std::chrono::system_clock::now();
-
         while (!writeConflict)
         {
             std::optional<org::xrpl::rpc::v1::GetLedgerResponse> fetchResponse{
@@ -894,6 +916,7 @@ ReportingETL::loadCache(uint32_t seq)
 {
     if (cacheLoadStyle_ == CacheLoadStyle::NOT_AT_ALL)
     {
+        backend_->cache().setDisabled();
         BOOST_LOG_TRIVIAL(warning) << "Cache is disabled. Not loading";
         return;
     }
@@ -915,7 +938,7 @@ ReportingETL::loadCache(uint32_t seq)
         a.insert(std::end(a), std::begin(b), std::end(b));
     };
 
-    for (size_t i = 0; i < numDiffs_; ++i)
+    for (size_t i = 0; i < numCacheDiffs_; ++i)
     {
         append(diff, Backend::synchronousAndRetryOnTimeout([&](auto yield) {
                    return backend_->fetchLedgerDiff(seq - i, yield);
@@ -950,55 +973,74 @@ ReportingETL::loadCache(uint32_t seq)
         << "Loading cache. num cursors = " << cursors.size() - 1;
     BOOST_LOG_TRIVIAL(debug) << __func__ << " cursors = " << cursorStr.str();
 
-    std::atomic_uint* numRemaining = new std::atomic_uint{cursors.size() - 1};
-
-    auto startTime = std::chrono::system_clock::now();
-    for (size_t i = 0; i < cursors.size() - 1; ++i)
-    {
-        std::optional<ripple::uint256> start = cursors[i];
-        std::optional<ripple::uint256> end = cursors[i + 1];
-        boost::asio::spawn(
-            ioContext_,
-            [this, seq, start, end, numRemaining, startTime](
-                boost::asio::yield_context yield) {
-                std::optional<ripple::uint256> cursor = start;
-                while (true)
-                {
-                    auto res =
-                        Backend::retryOnTimeout([this, seq, &cursor, &yield]() {
-                            return backend_->fetchLedgerPage(
-                                cursor, seq, 256, false, yield);
-                        });
-                    backend_->cache().update(res.objects, seq, true);
-                    if (!res.cursor || (end && *(res.cursor) > *end))
-                        break;
+    cacheDownloader_ = std::thread{[this, seq, cursors]() {
+        auto startTime = std::chrono::system_clock::now();
+        auto markers = std::make_shared<std::atomic_int>(0);
+        auto numRemaining =
+            std::make_shared<std::atomic_int>(cursors.size() - 1);
+        for (size_t i = 0; i < cursors.size() - 1; ++i)
+        {
+            std::optional<ripple::uint256> start = cursors[i];
+            std::optional<ripple::uint256> end = cursors[i + 1];
+            markers->wait(numCacheMarkers_);
+            ++(*markers);
+            boost::asio::spawn(
+                ioContext_,
+                [this, seq, start, end, numRemaining, startTime, markers](
+                    boost::asio::yield_context yield) {
+                    std::optional<ripple::uint256> cursor = start;
+                    std::string cursorStr = cursor.has_value()
+                        ? ripple::strHex(cursor.value())
+                        : ripple::strHex(Backend::firstKey);
                     BOOST_LOG_TRIVIAL(debug)
-                        << "Loading cache. cache size = "
-                        << backend_->cache().size()
-                        << " - cursor = " << ripple::strHex(res.cursor.value());
-                    cursor = std::move(res.cursor);
-                }
-                if (--(*numRemaining) == 0)
-                {
-                    auto endTime = std::chrono::system_clock::now();
-                    auto duration =
-                        std::chrono::duration_cast<std::chrono::seconds>(
-                            endTime - startTime);
-                    BOOST_LOG_TRIVIAL(info)
-                        << "Finished loading cache. cache size = "
-                        << backend_->cache().size() << ". Took "
-                        << duration.count() << " seconds";
-                    backend_->cache().setFull();
-                    delete numRemaining;
-                }
-                else
-                {
-                    BOOST_LOG_TRIVIAL(info)
-                        << "Finished a cursor. num remaining = "
-                        << *numRemaining;
-                }
-            });
-    }
+                        << "Starting a cursor: " << cursorStr
+                        << " markers = " << *markers;
+
+                    while (!stopping_)
+                    {
+                        auto res = Backend::retryOnTimeout([this,
+                                                            seq,
+                                                            &cursor,
+                                                            &yield]() {
+                            return backend_->fetchLedgerPage(
+                                cursor, seq, cachePageFetchSize_, false, yield);
+                        });
+                        backend_->cache().update(res.objects, seq, true);
+                        if (!res.cursor || (end && *(res.cursor) > *end))
+                            break;
+                        BOOST_LOG_TRIVIAL(debug)
+                            << "Loading cache. cache size = "
+                            << backend_->cache().size() << " - cursor = "
+                            << ripple::strHex(res.cursor.value())
+                            << " start = " << cursorStr
+                            << " markers = " << *markers;
+
+                        cursor = std::move(res.cursor);
+                    }
+                    --(*markers);
+                    markers->notify_one();
+                    if (--(*numRemaining) == 0)
+                    {
+                        auto endTime = std::chrono::system_clock::now();
+                        auto duration =
+                            std::chrono::duration_cast<std::chrono::seconds>(
+                                endTime - startTime);
+                        BOOST_LOG_TRIVIAL(info)
+                            << "Finished loading cache. cache size = "
+                            << backend_->cache().size() << ". Took "
+                            << duration.count() << " seconds";
+                        backend_->cache().setFull();
+                    }
+                    else
+                    {
+                        BOOST_LOG_TRIVIAL(info)
+                            << "Finished a cursor. num remaining = "
+                            << *numRemaining << " start = " << cursorStr
+                            << " markers = " << *markers;
+                    }
+                });
+        }
+    }};
     // If loading synchronously, poll cache until full
     while (cacheLoadStyle_ == CacheLoadStyle::SYNC &&
            !backend_->cache().isFull())
@@ -1108,9 +1150,12 @@ ReportingETL::ReportingETL(
             if (entry == "none" || entry == "no")
                 cacheLoadStyle_ = CacheLoadStyle::NOT_AT_ALL;
         }
-        if (cache.contains("num_diffs") && cache.at("num_diffs").as_int64())
-        {
-            numDiffs_ = cache.at("num_diffs").as_int64();
-        }
+        if (cache.contains("num_diffs") && cache.at("num_diffs").is_int64())
+            numCacheDiffs_ = cache.at("num_diffs").as_int64();
+        if (cache.contains("num_markers") && cache.at("num_markers").is_int64())
+            numCacheMarkers_ = cache.at("num_markers").as_int64();
+        if (cache.contains("page_fetch_size") &&
+            cache.at("page_fetch_size").is_int64())
+            cachePageFetchSize_ = cache.at("page_fetch_size").as_int64();
     }
 }

src/etl/ReportingETL.h

@@ -19,7 +19,22 @@
 
 #include <chrono>
 
+/**
+ * Helper function for the ReportingETL, implemented in NFTHelpers.cpp, to
+ * pull to-write data out of a transaction that relates to NFTs.
+ */
+std::pair<std::vector<NFTTransactionsData>, std::optional<NFTsData>>
+getNFTData(ripple::TxMeta const& txMeta, ripple::STTx const& sttx);
+
 struct AccountTransactionsData;
+struct NFTTransactionsData;
+struct NFTsData;
+struct FormattedTransactionsData
+{
+    std::vector<AccountTransactionsData> accountTxData;
+    std::vector<NFTTransactionsData> nfTokenTxData;
+    std::vector<NFTsData> nfTokensData;
+};
 class SubscriptionManager;
 
 /**
@@ -52,7 +67,15 @@ private:
 
     // number of diffs to use to generate cursors to traverse the ledger in
     // parallel during initial cache download
-    size_t numDiffs_ = 1;
+    size_t numCacheDiffs_ = 32;
+    // number of markers to use at one time to traverse the ledger in parallel
+    // during initial cache download
+    size_t numCacheMarkers_ = 48;
+    // number of ledger objects to fetch concurrently per marker during cache
+    // download
+    size_t cachePageFetchSize_ = 512;
+    // thread responsible for syncing the cache on startup
+    std::thread cacheDownloader_;
 
     std::thread worker_;
     boost::asio::io_context& ioContext_;
@@ -86,18 +109,6 @@ private:
     // deletion
     std::atomic_bool deleting_ = false;
 
-    /// Used to determine when to write to the database during the initial
-    /// ledger download. By default, the software downloads an entire ledger and
-    /// then writes to the database. If flushInterval_ is non-zero, the software
-    /// will write to the database as new ledger data (SHAMap leaf nodes)
-    /// arrives. It is not neccesarily more effient to write the data as it
-    /// arrives, as different SHAMap leaf nodes share the same SHAMap inner
-    /// nodes; flushing prematurely can result in the same SHAMap inner node
-    /// being written to the database more than once. It is recommended to use
-    /// the default value of 0 for this variable; however, different values can
-    /// be experimented with if better performance is desired.
-    size_t flushInterval_ = 0;
-
     /// This variable controls the number of GetLedgerData calls that will be
     /// executed in parallel during the initial ledger download. GetLedgerData
     /// allows clients to page through a ledger over many RPC calls.
@@ -123,29 +134,33 @@ private:
     std::optional<uint32_t> startSequence_;
     std::optional<uint32_t> finishSequence_;
 
-    size_t accumTxns_ = 0;
     size_t txnThreshold_ = 0;
 
     /// The time that the most recently published ledger was published. Used by
     /// server_info
     std::chrono::time_point<std::chrono::system_clock> lastPublish_;
 
-    mutable std::mutex publishTimeMtx_;
-
-    std::chrono::time_point<std::chrono::system_clock>
-    getLastPublish() const
-    {
-        std::unique_lock<std::mutex> lck(publishTimeMtx_);
-        return lastPublish_;
-    }
+    mutable std::shared_mutex publishTimeMtx_;
 
     void
     setLastPublish()
     {
-        std::unique_lock<std::mutex> lck(publishTimeMtx_);
+        std::unique_lock lck(publishTimeMtx_);
         lastPublish_ = std::chrono::system_clock::now();
     }
 
+    /// The time that the most recently published ledger was closed.
+    std::chrono::time_point<ripple::NetClock> lastCloseTime_;
+
+    mutable std::shared_mutex closeTimeMtx_;
+
+    void
+    setLastClose(std::chrono::time_point<ripple::NetClock> lastCloseTime)
+    {
+        std::unique_lock lck(closeTimeMtx_);
+        lastCloseTime_ = lastCloseTime;
+    }
+
     /// Download a ledger with specified sequence in full, via GetLedgerData,
     /// and write the data to the databases. This takes several minutes or
     /// longer.
@@ -208,14 +223,16 @@ private:
     std::optional<org::xrpl::rpc::v1::GetLedgerResponse>
     fetchLedgerDataAndDiff(uint32_t sequence);
 
-    /// Insert all of the extracted transactions into the ledger
+    /// Insert all of the extracted transactions into the ledger, returning
+    /// transactions related to accounts, transactions related to NFTs, and
+    /// NFTs themselves for later processsing.
     /// @param ledger ledger to insert transactions into
     /// @param data data extracted from an ETL source
     /// @return struct that contains the neccessary info to write to the
-    /// transctions and account_transactions tables in Postgres (mostly
-    /// transaction hashes, corresponding nodestore hashes and affected
+    /// account_transactions/account_tx and nft_token_transactions tables
+    /// (mostly transaction hashes, corresponding nodestore hashes and affected
     /// accounts)
-    std::vector<AccountTransactionsData>
+    FormattedTransactionsData
     insertTransactions(
         ripple::LedgerInfo const& ledger,
         org::xrpl::rpc::v1::GetLedgerResponse& data);
@@ -308,6 +325,8 @@ public:
 
         if (worker_.joinable())
             worker_.join();
+        if (cacheDownloader_.joinable())
+            cacheDownloader_.join();
 
         BOOST_LOG_TRIVIAL(debug) << "Joined ReportingETL worker thread";
     }
@@ -322,13 +341,38 @@ public:
         result["read_only"] = readOnly_;
         auto last = getLastPublish();
         if (last.time_since_epoch().count() != 0)
-            result["last_publish_age_seconds"] = std::to_string(
-                std::chrono::duration_cast<std::chrono::seconds>(
-                    std::chrono::system_clock::now() - getLastPublish())
-                    .count());
-
+            result["last_publish_age_seconds"] =
+                std::to_string(lastPublishAgeSeconds());
         return result;
     }
+
+    std::chrono::time_point<std::chrono::system_clock>
+    getLastPublish() const
+    {
+        std::shared_lock lck(publishTimeMtx_);
+        return lastPublish_;
+    }
+
+    std::uint32_t
+    lastPublishAgeSeconds() const
+    {
+        return std::chrono::duration_cast<std::chrono::seconds>(
+                   std::chrono::system_clock::now() - getLastPublish())
+            .count();
+    }
+
+    std::uint32_t
+    lastCloseAgeSeconds() const
+    {
+        std::shared_lock lck(closeTimeMtx_);
+        auto now = std::chrono::duration_cast<std::chrono::seconds>(
+                       std::chrono::system_clock::now().time_since_epoch())
+                       .count();
+        auto closeTime = lastCloseTime_.time_since_epoch().count();
+        if (now < (rippleEpochStart + closeTime))
+            return 0;
+        return now - (rippleEpochStart + closeTime);
+    }
 };
 
 #endif

src/main/Build.h

@@ -0,0 +1,16 @@
+#ifndef CLIO_BUILD_INFO_H
+#define CLIO_BUILD_INFO_H
+
+#include <string>
+
+namespace Build {
+
+std::string const&
+getClioVersionString();
+
+std::string const&
+getClioFullVersionString();
+
+}  // namespace Build
+
+#endif  // CLIO_BUILD_INFO_H

src/main/impl/Build.cpp

@@ -0,0 +1,59 @@
+#include <ripple/beast/core/SemanticVersion.h>
+#include <boost/preprocessor/stringize.hpp>
+#include <algorithm>
+#include <main/Build.h>
+#include <optional>
+#include <stdexcept>
+
+namespace Build {
+
+//--------------------------------------------------------------------------
+//  The build version number. You must edit this for each release
+//  and follow the format described at http://semver.org/
+//------------------------------------------------------------------------------
+// clang-format off
+char const* const versionString = "1.0.3"
+// clang-format on
+
+#if defined(DEBUG) || defined(SANITIZER)
+    "+"
+#ifdef CLIO_GIT_COMMIT_HASH
+    CLIO_GIT_COMMIT_HASH
+    "."
+#endif
+#ifdef DEBUG
+    "DEBUG"
+#ifdef SANITIZER
+    "."
+#endif
+#endif
+
+#ifdef SANITIZER
+    BOOST_PP_STRINGIZE(SANITIZER)
+#endif
+#endif
+
+    //--------------------------------------------------------------------------
+    ;
+
+std::string const&
+getClioVersionString()
+{
+    static std::string const value = [] {
+        std::string const s = versionString;
+        beast::SemanticVersion v;
+        if (!v.parse(s) || v.print() != s)
+            throw std::runtime_error(s + ": Bad server version string");
+        return s;
+    }();
+    return value;
+}
+
+std::string const&
+getClioFullVersionString()
+{
+    static std::string const value = "clio-" + getClioVersionString();
+    return value;
+}
+
+}  // namespace Build

src/main/main.cpp

@@ -28,6 +28,7 @@
 #include <fstream>
 #include <functional>
 #include <iostream>
+#include <main/Build.h>
 #include <memory>
 #include <sstream>
 #include <string>
@@ -103,45 +104,85 @@ parse_certs(boost::json::object const& config)
 void
 initLogging(boost::json::object const& config)
 {
+    namespace src = boost::log::sources;
+    namespace keywords = boost::log::keywords;
+    namespace sinks = boost::log::sinks;
+    namespace trivial = boost::log::trivial;
     boost::log::add_common_attributes();
     std::string format = "[%TimeStamp%] [%ThreadID%] [%Severity%] %Message%";
-    boost::log::add_console_log(
-        std::cout, boost::log::keywords::format = format);
-    if (config.contains("log_file"))
+    if (!config.contains("log_to_console") ||
+        config.at("log_to_console").as_bool())
     {
-        boost::log::add_file_log(
-            config.at("log_file").as_string().c_str(),
-            boost::log::keywords::format = format,
-            boost::log::keywords::open_mode = std::ios_base::app);
+        boost::log::add_console_log(std::cout, keywords::format = format);
+    }
+    if (config.contains("log_directory"))
+    {
+        if (!config.at("log_directory").is_string())
+            throw std::runtime_error("log directory must be a string");
+        boost::filesystem::path dirPath{
+            config.at("log_directory").as_string().c_str()};
+        if (!boost::filesystem::exists(dirPath))
+            boost::filesystem::create_directories(dirPath);
+        const int64_t rotationSize = config.contains("log_rotation_size")
+            ? config.at("log_rotation_size").as_int64() * 1024 * 1024u
+            : 2 * 1024 * 1024 * 1024u;
+        if (rotationSize <= 0)
+            throw std::runtime_error(
+                "log rotation size must be greater than 0");
+        const int64_t rotationPeriod =
+            config.contains("log_rotation_hour_interval")
+            ? config.at("log_rotation_hour_interval").as_int64()
+            : 12u;
+        if (rotationPeriod <= 0)
+            throw std::runtime_error(
+                "log rotation time interval must be greater than 0");
+        const int64_t dirSize = config.contains("log_directory_max_size")
+            ? config.at("log_directory_max_size").as_int64() * 1024 * 1024u
+            : 50 * 1024 * 1024 * 1024u;
+        if (dirSize <= 0)
+            throw std::runtime_error(
+                "log rotation directory max size must be greater than 0");
+        auto fileSink = boost::log::add_file_log(
+            keywords::file_name = dirPath / "clio.log",
+            keywords::target_file_name = dirPath / "clio_%Y-%m-%d_%H-%M-%S.log",
+            keywords::auto_flush = true,
+            keywords::format = format,
+            keywords::open_mode = std::ios_base::app,
+            keywords::rotation_size = rotationSize,
+            keywords::time_based_rotation =
+                sinks::file::rotation_at_time_interval(
+                    boost::posix_time::hours(rotationPeriod)));
+        fileSink->locked_backend()->set_file_collector(
+            sinks::file::make_collector(
+                keywords::target = dirPath, keywords::max_size = dirSize));
+        fileSink->locked_backend()->scan_for_files();
     }
     auto const logLevel = config.contains("log_level")
         ? config.at("log_level").as_string()
         : "info";
     if (boost::iequals(logLevel, "trace"))
         boost::log::core::get()->set_filter(
-            boost::log::trivial::severity >= boost::log::trivial::trace);
+            trivial::severity >= trivial::trace);
     else if (boost::iequals(logLevel, "debug"))
         boost::log::core::get()->set_filter(
-            boost::log::trivial::severity >= boost::log::trivial::debug);
+            trivial::severity >= trivial::debug);
     else if (boost::iequals(logLevel, "info"))
-        boost::log::core::get()->set_filter(
-            boost::log::trivial::severity >= boost::log::trivial::info);
+        boost::log::core::get()->set_filter(trivial::severity >= trivial::info);
     else if (
         boost::iequals(logLevel, "warning") || boost::iequals(logLevel, "warn"))
         boost::log::core::get()->set_filter(
-            boost::log::trivial::severity >= boost::log::trivial::warning);
+            trivial::severity >= trivial::warning);
     else if (boost::iequals(logLevel, "error"))
         boost::log::core::get()->set_filter(
-            boost::log::trivial::severity >= boost::log::trivial::error);
+            trivial::severity >= trivial::error);
     else if (boost::iequals(logLevel, "fatal"))
         boost::log::core::get()->set_filter(
-            boost::log::trivial::severity >= boost::log::trivial::fatal);
+            trivial::severity >= trivial::fatal);
     else
     {
         BOOST_LOG_TRIVIAL(warning) << "Unrecognized log level: " << logLevel
                                    << ". Setting log level to info";
-        boost::log::core::get()->set_filter(
-            boost::log::trivial::severity >= boost::log::trivial::info);
+        boost::log::core::get()->set_filter(trivial::severity >= trivial::info);
     }
     BOOST_LOG_TRIVIAL(info) << "Log level = " << logLevel;
 }
@@ -170,6 +211,12 @@ main(int argc, char* argv[])
         return EXIT_FAILURE;
     }
 
+    if (std::string{argv[1]} == "-v" || std::string{argv[1]} == "--version")
+    {
+        std::cout << Build::getClioFullVersionString() << std::endl;
+        return EXIT_SUCCESS;
+    }
+
     auto const config = parse_config(argv[1]);
     if (!config)
     {
@@ -179,21 +226,25 @@ main(int argc, char* argv[])
 
     initLogging(*config);
 
+    // Announce Clio version
+    BOOST_LOG_TRIVIAL(info)
+        << "Clio version: " << Build::getClioFullVersionString();
+
     auto ctx = parse_certs(*config);
     auto ctxRef = ctx
         ? std::optional<std::reference_wrapper<ssl::context>>{ctx.value()}
         : std::nullopt;
 
-    auto const threads = config->contains("workers")
-        ? config->at("workers").as_int64()
-        : std::thread::hardware_concurrency();
+    auto const threads = config->contains("io_threads")
+        ? config->at("io_threads").as_int64()
+        : 2;
 
     if (threads <= 0)
     {
-        BOOST_LOG_TRIVIAL(fatal) << "Workers is less than 0";
+        BOOST_LOG_TRIVIAL(fatal) << "io_threads is less than 0";
         return EXIT_FAILURE;
     }
-    BOOST_LOG_TRIVIAL(info) << "Number of workers = " << threads;
+    BOOST_LOG_TRIVIAL(info) << "Number of io threads = " << threads;
 
     // io context to handle all incoming requests, as well as other things
     // This is not the only io context in the application
@@ -221,7 +272,7 @@ main(int argc, char* argv[])
     // The balancer itself publishes to streams (transactions_proposed and
     // accounts_proposed)
     auto balancer = ETLLoadBalancer::make_ETLLoadBalancer(
-        *config, ioc, ctxRef, backend, subscriptions, ledgers);
+        *config, ioc, backend, subscriptions, ledgers);
 
     // ETL is responsible for writing and publishing to streams. In read-only
     // mode, ETL only publishes

src/rpc/Counters.h

@@ -6,6 +6,7 @@
 #include <cstdint>
 #include <shared_mutex>
 #include <string>
+#include <unordered_map>
 
 namespace RPC {
 

src/rpc/Handlers.h

@@ -21,6 +21,9 @@ doAccountCurrencies(Context const& context);
 Result
 doAccountLines(Context const& context);
 
+Result
+doAccountNFTs(Context const& context);
+
 Result
 doAccountObjects(Context const& context);
 
@@ -41,10 +44,23 @@ doChannelAuthorize(Context const& context);
 Result
 doChannelVerify(Context const& context);
 
-// offers methods
+// book methods
+Result
+doBookChanges(Context const& context);
+
 Result
 doBookOffers(Context const& context);
 
+// NFT methods
+Result
+doNFTBuyOffers(Context const& context);
+
+Result
+doNFTSellOffers(Context const& context);
+
+Result
+doNFTInfo(Context const& context);
+
 // ledger methods
 Result
 doLedger(Context const& context);

src/rpc/RPC.cpp

@@ -1,6 +1,7 @@
 #include <boost/asio/spawn.hpp>
 #include <etl/ETLSource.h>
 #include <rpc/Handlers.h>
+#include <rpc/RPCHelpers.h>
 #include <unordered_map>
 
 namespace RPC {
@@ -90,6 +91,38 @@ make_HttpContext(
         clientIp};
 }
 
+constexpr static WarningInfo warningInfos[]{
+    {warnUNKNOWN, "Unknown warning"},
+    {warnRPC_CLIO,
+     "This is a clio server. clio only serves validated data. If you "
+     "want to talk to rippled, include 'ledger_index':'current' in your "
+     "request"},
+    {warnRPC_OUTDATED, "This server may be out of date"},
+    {warnRPC_RATE_LIMIT, "You are about to be rate limited"}};
+
+WarningInfo const&
+get_warning_info(warning_code code)
+{
+    for (WarningInfo const& info : warningInfos)
+    {
+        if (info.code == code)
+        {
+            return info;
+        }
+    }
+    throw(std::out_of_range("Invalid warning_code"));
+}
+
+boost::json::object
+make_warning(warning_code code)
+{
+    boost::json::object json;
+    WarningInfo const& info(get_warning_info(code));
+    json["id"] = code;
+    json["message"] = static_cast<std::string>(info.message);
+    return json;
+}
+
 boost::json::object
 make_error(Error err)
 {
@@ -106,6 +139,14 @@ make_error(Error err)
 boost::json::object
 make_error(Status const& status)
 {
+    if (status.error == ripple::rpcUNKNOWN)
+    {
+        return {
+            {"error", status.message},
+            {"type", "response"},
+            {"status", "error"}};
+    }
+
     boost::json::object json;
     ripple::RPC::ErrorInfo const& info(
         ripple::RPC::get_error_info(status.error));
@@ -118,31 +159,81 @@ make_error(Status const& status)
     json["type"] = "response";
     return json;
 }
-static std::unordered_map<std::string, std::function<Result(Context const&)>>
-    handlerTable{
-        {"account_channels", &doAccountChannels},
-        {"account_currencies", &doAccountCurrencies},
-        {"account_info", &doAccountInfo},
-        {"account_lines", &doAccountLines},
-        {"account_objects", &doAccountObjects},
-        {"account_offers", &doAccountOffers},
-        {"account_tx", &doAccountTx},
-        {"gateway_balances", &doGatewayBalances},
-        {"noripple_check", &doNoRippleCheck},
-        {"book_offers", &doBookOffers},
-        {"channel_authorize", &doChannelAuthorize},
-        {"channel_verify", &doChannelVerify},
-        {"ledger", &doLedger},
-        {"ledger_data", &doLedgerData},
-        {"ledger_entry", &doLedgerEntry},
-        {"ledger_range", &doLedgerRange},
-        {"ledger_data", &doLedgerData},
-        {"subscribe", &doSubscribe},
-        {"server_info", &doServerInfo},
-        {"unsubscribe", &doUnsubscribe},
-        {"tx", &doTx},
-        {"transaction_entry", &doTransactionEntry},
-        {"random", &doRandom}};
+
+using LimitRange = std::tuple<std::uint32_t, std::uint32_t, std::uint32_t>;
+using HandlerFunction = std::function<Result(Context const&)>;
+
+struct Handler
+{
+    std::string method;
+    std::function<Result(Context const&)> handler;
+    std::optional<LimitRange> limit;
+};
+
+class HandlerTable
+{
+    std::unordered_map<std::string, Handler> handlerMap_;
+
+public:
+    HandlerTable(std::initializer_list<Handler> handlers)
+    {
+        for (auto const& handler : handlers)
+        {
+            handlerMap_[handler.method] = std::move(handler);
+        }
+    }
+
+    bool
+    contains(std::string const& method)
+    {
+        return handlerMap_.contains(method);
+    }
+
+    std::optional<LimitRange>
+    getLimitRange(std::string const& command)
+    {
+        if (!handlerMap_.contains(command))
+            return {};
+
+        return handlerMap_[command].limit;
+    }
+
+    std::optional<HandlerFunction>
+    getHandler(std::string const& command)
+    {
+        if (!handlerMap_.contains(command))
+            return {};
+
+        return handlerMap_[command].handler;
+    }
+};
+
+static HandlerTable handlerTable{
+    {"account_channels", &doAccountChannels, LimitRange{10, 50, 256}},
+    {"account_currencies", &doAccountCurrencies, {}},
+    {"account_info", &doAccountInfo, {}},
+    {"account_lines", &doAccountLines, LimitRange{10, 50, 256}},
+    {"account_nfts", &doAccountNFTs, LimitRange{1, 5, 10}},
+    {"account_objects", &doAccountObjects, LimitRange{10, 50, 256}},
+    {"account_offers", &doAccountOffers, LimitRange{10, 50, 256}},
+    {"account_tx", &doAccountTx, LimitRange{1, 50, 100}},
+    {"gateway_balances", &doGatewayBalances, {}},
+    {"noripple_check", &doNoRippleCheck, {}},
+    {"book_changes", &doBookChanges, {}},
+    {"book_offers", &doBookOffers, LimitRange{1, 50, 100}},
+    {"ledger", &doLedger, {}},
+    {"ledger_data", &doLedgerData, LimitRange{1, 100, 2048}},
+    {"nft_buy_offers", &doNFTBuyOffers, LimitRange{1, 50, 100}},
+    {"nft_info", &doNFTInfo},
+    {"nft_sell_offers", &doNFTSellOffers, LimitRange{1, 50, 100}},
+    {"ledger_entry", &doLedgerEntry, {}},
+    {"ledger_range", &doLedgerRange, {}},
+    {"subscribe", &doSubscribe, {}},
+    {"server_info", &doServerInfo, {}},
+    {"unsubscribe", &doUnsubscribe, {}},
+    {"tx", &doTx, {}},
+    {"transaction_entry", &doTransactionEntry, {}},
+    {"random", &doRandom, {}}};
 
 static std::unordered_set<std::string> forwardCommands{
     "submit",
@@ -151,7 +242,9 @@ static std::unordered_set<std::string> forwardCommands{
     "ledger_closed",
     "ledger_current",
     "ripple_path_find",
-    "manifest"};
+    "manifest",
+    "channel_authorize",
+    "channel_verify"};
 
 bool
 validHandler(std::string const& method)
@@ -159,6 +252,36 @@ validHandler(std::string const& method)
     return handlerTable.contains(method) || forwardCommands.contains(method);
 }
 
+Status
+getLimit(RPC::Context const& context, std::uint32_t& limit)
+{
+    if (!handlerTable.getHandler(context.method))
+        return Status{Error::rpcUNKNOWN_COMMAND};
+
+    if (!handlerTable.getLimitRange(context.method))
+        return Status{Error::rpcINVALID_PARAMS, "rpcDoesNotRequireLimit"};
+
+    auto [lo, def, hi] = *handlerTable.getLimitRange(context.method);
+
+    if (context.params.contains(JS(limit)))
+    {
+        if (!context.params.at(JS(limit)).is_int64())
+            return Status{Error::rpcINVALID_PARAMS, "limitNotInt"};
+
+        limit = context.params.at(JS(limit)).as_int64();
+        if (limit <= 0)
+            return Status{Error::rpcINVALID_PARAMS, "limitNotPositive"};
+
+        limit = std::clamp(limit, lo, hi);
+    }
+    else
+    {
+        limit = def;
+    }
+
+    return {};
+}
+
 bool
 shouldForwardToRippled(Context const& ctx)
 {
@@ -167,15 +290,8 @@ shouldForwardToRippled(Context const& ctx)
     if (forwardCommands.find(ctx.method) != forwardCommands.end())
         return true;
 
-    if (request.contains("ledger_index"))
-    {
-        auto indexValue = request.at("ledger_index");
-        if (indexValue.is_string())
-        {
-            std::string index = indexValue.as_string().c_str();
-            return index == "current" || index == "closed";
-        }
-    }
+    if (specifiesCurrentOrClosedLedger(request))
+        return true;
 
     if (ctx.method == "account_info" && request.contains("queue") &&
         request.at("queue").as_bool())
@@ -209,14 +325,14 @@ buildResponse(Context const& ctx)
     if (ctx.method == "ping")
         return boost::json::object{};
 
-    if (handlerTable.find(ctx.method) == handlerTable.end())
-        return Status{Error::rpcUNKNOWN_COMMAND};
+    auto method = handlerTable.getHandler(ctx.method);
 
-    auto method = handlerTable[ctx.method];
+    if (!method)
+        return Status{Error::rpcUNKNOWN_COMMAND};
 
     try
     {
-        auto v = method(ctx);
+        auto v = (*method)(ctx);
 
         if (auto object = std::get_if<boost::json::object>(&v))
             (*object)["validated"] = true;
@@ -235,7 +351,7 @@ buildResponse(Context const& ctx)
     {
         BOOST_LOG_TRIVIAL(error)
             << __func__ << " caught exception : " << err.what();
-        return Status{Error::rpcINTERNAL, err.what()};
+        return Status{Error::rpcINTERNAL};
     }
 }
 

src/rpc/RPC.h

@@ -103,10 +103,19 @@ struct Status
 
     Status(Error error_) : error(error_){};
 
+    // HACK. Some rippled handlers explicitly specify errors.
+    // This means that we have to be able to duplicate this
+    // functionality.
+    Status(std::string const& message_)
+        : error(ripple::rpcUNKNOWN), message(message_)
+    {
+    }
+
     Status(Error error_, std::string message_)
         : error(error_), message(message_)
     {
     }
+
     Status(Error error_, std::string strCode_, std::string message_)
         : error(error_), strCode(strCode_), message(message_)
     {
@@ -153,6 +162,33 @@ public:
     }
 };
 
+enum warning_code {
+    warnUNKNOWN = -1,
+    warnRPC_CLIO = 2001,
+    warnRPC_OUTDATED = 2002,
+    warnRPC_RATE_LIMIT = 2003
+};
+
+struct WarningInfo
+{
+    constexpr WarningInfo() : code(warnUNKNOWN), message("unknown warning")
+    {
+    }
+
+    constexpr WarningInfo(warning_code code_, char const* message_)
+        : code(code_), message(message_)
+    {
+    }
+    warning_code code;
+    std::string_view const message;
+};
+
+WarningInfo const&
+get_warning_info(warning_code code);
+
+boost::json::object
+make_warning(warning_code code);
+
 boost::json::object
 make_error(Status const& status);
 
@@ -190,6 +226,9 @@ buildResponse(Context const& ctx);
 bool
 validHandler(std::string const& method);
 
+Status
+getLimit(RPC::Context const& context, std::uint32_t& limit);
+
 template <class T>
 void
 logDuration(Context const& ctx, T const& dur)
@@ -205,7 +244,7 @@ logDuration(Context const& ctx, T const& dur)
     else if (seconds > 1)
         BOOST_LOG_TRIVIAL(warning) << ss.str();
     else
-        BOOST_LOG_TRIVIAL(debug) << ss.str();
+        BOOST_LOG_TRIVIAL(info) << ss.str();
 }
 
 }  // namespace RPC

src/rpc/RPCHelpers.cpp

@@ -13,6 +13,7 @@ getBool(boost::json::object const& request, std::string const& field)
     else
         throw InvalidParamsError("Invalid field " + field + ", not bool.");
 }
+
 bool
 getBool(
     boost::json::object const& request,
@@ -24,6 +25,7 @@ getBool(
     else
         return dfault;
 }
+
 bool
 getRequiredBool(boost::json::object const& request, std::string const& field)
 {
@@ -152,6 +154,7 @@ getString(boost::json::object const& request, std::string const& field)
     else
         throw InvalidParamsError("Invalid field " + field + ", not string.");
 }
+
 std::string
 getRequiredString(boost::json::object const& request, std::string const& field)
 {
@@ -160,6 +163,7 @@ getRequiredString(boost::json::object const& request, std::string const& field)
     else
         throw InvalidParamsError("Missing field " + field);
 }
+
 std::string
 getString(
     boost::json::object const& request,
@@ -172,11 +176,128 @@ getString(
         return dfault;
 }
 
+Status
+getHexMarker(boost::json::object const& request, ripple::uint256& marker)
+{
+    if (request.contains(JS(marker)))
+    {
+        if (!request.at(JS(marker)).is_string())
+            return Status{Error::rpcINVALID_PARAMS, "markerNotString"};
+
+        if (!marker.parseHex(request.at(JS(marker)).as_string().c_str()))
+            return Status{Error::rpcINVALID_PARAMS, "malformedMarker"};
+    }
+
+    return {};
+}
+
+Status
+getAccount(
+    boost::json::object const& request,
+    ripple::AccountID& account,
+    boost::string_view const& field,
+    bool required)
+{
+    if (!request.contains(field))
+    {
+        if (required)
+            return Status{
+                Error::rpcINVALID_PARAMS, field.to_string() + "Missing"};
+
+        return {};
+    }
+
+    if (!request.at(field).is_string())
+        return Status{
+            Error::rpcINVALID_PARAMS, field.to_string() + "NotString"};
+
+    if (auto a = accountFromStringStrict(request.at(field).as_string().c_str());
+        a)
+    {
+        account = a.value();
+        return {};
+    }
+
+    return Status{Error::rpcINVALID_PARAMS, field.to_string() + "Malformed"};
+}
+
+Status
+getOptionalAccount(
+    boost::json::object const& request,
+    std::optional<ripple::AccountID>& account,
+    boost::string_view const& field)
+{
+    if (!request.contains(field))
+    {
+        account = {};
+        return {};
+    }
+
+    if (!request.at(field).is_string())
+        return Status{
+            Error::rpcINVALID_PARAMS, field.to_string() + "NotString"};
+
+    if (auto a = accountFromStringStrict(request.at(field).as_string().c_str());
+        a)
+    {
+        account = a.value();
+        return {};
+    }
+
+    return Status{Error::rpcINVALID_PARAMS, field.to_string() + "Malformed"};
+}
+
+Status
+getAccount(boost::json::object const& request, ripple::AccountID& accountId)
+{
+    return getAccount(request, accountId, JS(account), true);
+}
+
+Status
+getAccount(
+    boost::json::object const& request,
+    ripple::AccountID& destAccount,
+    boost::string_view const& field)
+{
+    return getAccount(request, destAccount, field, false);
+}
+
+Status
+getTaker(boost::json::object const& request, ripple::AccountID& takerID)
+{
+    if (request.contains(JS(taker)))
+    {
+        auto parsed = parseTaker(request.at(JS(taker)));
+        if (auto status = std::get_if<Status>(&parsed))
+            return *status;
+        else
+            takerID = std::get<ripple::AccountID>(parsed);
+    }
+
+    return {};
+}
+
+Status
+getChannelId(boost::json::object const& request, ripple::uint256& channelId)
+{
+    if (!request.contains(JS(channel_id)))
+        return Status{Error::rpcINVALID_PARAMS, "missingChannelID"};
+
+    if (!request.at(JS(channel_id)).is_string())
+        return Status{Error::rpcINVALID_PARAMS, "channelIDNotString"};
+
+    if (!channelId.parseHex(request.at(JS(channel_id)).as_string().c_str()))
+        return Status{Error::rpcCHANNEL_MALFORMED, "malformedChannelID"};
+
+    return {};
+}
+
 std::optional<ripple::STAmount>
 getDeliveredAmount(
     std::shared_ptr<ripple::STTx const> const& txn,
     std::shared_ptr<ripple::TxMeta const> const& meta,
-    std::uint32_t const ledgerSequence)
+    std::uint32_t const ledgerSequence,
+    uint32_t date)
 {
     if (meta->hasDeliveredAmount())
         return meta->getDeliveredAmount();
@@ -192,7 +313,7 @@ getDeliveredAmount(
         // then its absence indicates that the amount delivered is listed in the
         // Amount field. DeliveredAmount went live January 24, 2014.
         // 446000000 is in Feb 2014, well after DeliveredAmount went live
-        if (ledgerSequence >= 4594095)
+        if (ledgerSequence >= 4594095 || date > 446000000)
         {
             return txn->getFieldAmount(ripple::sfAmount);
         }
@@ -338,7 +459,7 @@ toExpandedJson(Backend::TransactionAndMetadata const& blobs)
     auto [txn, meta] = deserializeTxPlusMeta(blobs, blobs.ledgerSequence);
     auto txnJson = toJson(*txn);
     auto metaJson = toJson(*meta);
-    insertDeliveredAmount(metaJson, txn, meta);
+    insertDeliveredAmount(metaJson, txn, meta, blobs.date);
     return {txnJson, metaJson};
 }
 
@@ -346,11 +467,12 @@ bool
 insertDeliveredAmount(
     boost::json::object& metaJson,
     std::shared_ptr<ripple::STTx const> const& txn,
-    std::shared_ptr<ripple::TxMeta const> const& meta)
+    std::shared_ptr<ripple::TxMeta const> const& meta,
+    uint32_t date)
 {
     if (canHaveDeliveredAmount(txn, meta))
     {
-        if (auto amt = getDeliveredAmount(txn, meta, meta->getLgrSeq()))
+        if (auto amt = getDeliveredAmount(txn, meta, meta->getLgrSeq(), date))
             metaJson["delivered_amount"] =
                 toBoostJson(amt->getJson(ripple::JsonOptions::include_date));
         else
@@ -448,6 +570,11 @@ ledgerInfoFromRequest(Context const& ctx)
             return Status{Error::rpcINVALID_PARAMS, "ledgerHashMalformed"};
 
         auto lgrInfo = ctx.backend->fetchLedgerByHash(ledgerHash, ctx.yield);
+
+        if (!lgrInfo || lgrInfo->seq > ctx.range.maxSequence)
+            return Status{Error::rpcLGR_NOT_FOUND, "ledgerNotFound"};
+
+        return *lgrInfo;
     }
 
     auto indexValue = ctx.params.contains("ledger_index")
@@ -479,7 +606,7 @@ ledgerInfoFromRequest(Context const& ctx)
     auto lgrInfo =
         ctx.backend->fetchLedgerBySequence(*ledgerSequence, ctx.yield);
 
-    if (!lgrInfo)
+    if (!lgrInfo || lgrInfo->seq > ctx.range.maxSequence)
         return Status{Error::rpcLGR_NOT_FOUND, "ledgerNotFound"};
 
     return *lgrInfo;
@@ -537,20 +664,47 @@ traverseOwnedNodes(
     if (!parsedCursor)
         return Status(ripple::rpcINVALID_PARAMS, "Malformed cursor");
 
-    auto cursor = AccountCursor({beast::zero, 0});
-
     auto [hexCursor, startHint] = *parsedCursor;
 
-    auto const rootIndex = ripple::keylet::ownerDir(accountID);
+    return traverseOwnedNodes(
+        backend,
+        ripple::keylet::ownerDir(accountID),
+        hexCursor,
+        startHint,
+        sequence,
+        limit,
+        jsonCursor,
+        yield,
+        atOwnedNode);
+}
+
+std::variant<Status, AccountCursor>
+traverseOwnedNodes(
+    BackendInterface const& backend,
+    ripple::Keylet const& owner,
+    ripple::uint256 const& hexMarker,
+    std::uint32_t const startHint,
+    std::uint32_t sequence,
+    std::uint32_t limit,
+    std::optional<std::string> jsonCursor,
+    boost::asio::yield_context& yield,
+    std::function<void(ripple::SLE)> atOwnedNode)
+{
+    auto cursor = AccountCursor({beast::zero, 0});
+
+    auto const rootIndex = owner;
     auto currentIndex = rootIndex;
 
     std::vector<ripple::uint256> keys;
-    keys.reserve(limit);
+    // Only reserve 2048 nodes when fetching all owned ledger objects. If there
+    // are more, then keys will allocate more memory, which is suboptimal, but
+    // should only occur occasionally.
+    keys.reserve(std::min(std::uint32_t{2048}, limit));
 
     auto start = std::chrono::system_clock::now();
 
     // If startAfter is not zero try jumping to that page using the hint
-    if (hexCursor.isNonZero())
+    if (hexMarker.isNonZero())
     {
         auto const hintIndex = ripple::keylet::page(rootIndex, startHint);
         auto hintDir =
@@ -563,7 +717,7 @@ traverseOwnedNodes(
 
             for (auto const& key : sle.getFieldV256(ripple::sfIndexes))
             {
-                if (key == hexCursor)
+                if (key == hexMarker)
                 {
                     // We found the hint, we can start here
                     currentIndex = hintIndex;
@@ -589,7 +743,7 @@ traverseOwnedNodes(
             {
                 if (!found)
                 {
-                    if (key == hexCursor)
+                    if (key == hexMarker)
                         found = true;
                 }
                 else
@@ -625,7 +779,7 @@ traverseOwnedNodes(
                 backend.fetchLedgerObject(currentIndex.key, sequence, yield);
 
             if (!ownerDir)
-                return Status(ripple::rpcACT_NOT_FOUND);
+                break;
 
             ripple::SerialIter it{ownerDir->data(), ownerDir->size()};
             ripple::SLE sle{it, currentIndex.key};
@@ -678,6 +832,23 @@ traverseOwnedNodes(
     return AccountCursor({beast::zero, 0});
 }
 
+std::shared_ptr<ripple::SLE const>
+read(
+    ripple::Keylet const& keylet,
+    ripple::LedgerInfo const& lgrInfo,
+    Context const& context)
+{
+    if (auto const blob = context.backend->fetchLedgerObject(
+            keylet.key, lgrInfo.seq, context.yield);
+        blob)
+    {
+        return std::make_shared<ripple::SLE const>(
+            ripple::SerialIter{blob->data(), blob->size()}, keylet.key);
+    }
+
+    return nullptr;
+}
+
 std::optional<ripple::Seed>
 parseRippleLibSeed(boost::json::value const& value)
 {
@@ -1280,6 +1451,7 @@ parseBook(boost::json::object const& request)
 
     return ripple::Book{{pay_currency, pay_issuer}, {get_currency, get_issuer}};
 }
+
 std::variant<Status, ripple::AccountID>
 parseTaker(boost::json::value const& taker)
 {
@@ -1293,5 +1465,19 @@ parseTaker(boost::json::value const& taker)
         return Status{Error::rpcINVALID_PARAMS, "invalidTakerAccount"};
     return *takerID;
 }
+bool
+specifiesCurrentOrClosedLedger(boost::json::object const& request)
+{
+    if (request.contains("ledger_index"))
+    {
+        auto indexValue = request.at("ledger_index");
+        if (indexValue.is_string())
+        {
+            std::string index = indexValue.as_string().c_str();
+            return index == "current" || index == "closed";
+        }
+    }
+    return false;
+}
 
 }  // namespace RPC

src/rpc/RPCHelpers.h

@@ -14,6 +14,13 @@
 #include <backend/BackendInterface.h>
 #include <rpc/RPC.h>
 
+// Useful macro for borrowing from ripple::jss
+// static strings. (J)son (S)trings
+#define JS(x) ripple::jss::x.c_str()
+
+// Access (SF)ield name (S)trings
+#define SFS(x) ripple::x.jsonName.c_str()
+
 namespace RPC {
 std::optional<ripple::AccountID>
 accountFromStringStrict(std::string const& account);
@@ -55,7 +62,8 @@ bool
 insertDeliveredAmount(
     boost::json::object& metaJson,
     std::shared_ptr<ripple::STTx const> const& txn,
-    std::shared_ptr<ripple::TxMeta const> const& meta);
+    std::shared_ptr<ripple::TxMeta const> const& meta,
+    uint32_t date);
 
 boost::json::object
 toJson(ripple::STBase const& obj);
@@ -93,6 +101,24 @@ traverseOwnedNodes(
     boost::asio::yield_context& yield,
     std::function<void(ripple::SLE)> atOwnedNode);
 
+std::variant<Status, AccountCursor>
+traverseOwnedNodes(
+    BackendInterface const& backend,
+    ripple::Keylet const& owner,
+    ripple::uint256 const& hexMarker,
+    std::uint32_t const startHint,
+    std::uint32_t sequence,
+    std::uint32_t limit,
+    std::optional<std::string> jsonCursor,
+    boost::asio::yield_context& yield,
+    std::function<void(ripple::SLE)> atOwnedNode);
+
+std::shared_ptr<ripple::SLE const>
+read(
+    ripple::Keylet const& keylet,
+    ripple::LedgerInfo const& lgrInfo,
+    Context const& context);
+
 std::variant<Status, std::pair<ripple::PublicKey, ripple::SecretKey>>
 keypairFromRequst(boost::json::object const& request);
 
@@ -200,5 +226,33 @@ getString(
     boost::json::object const& request,
     std::string const& field,
     std::string dfault);
+
+Status
+getHexMarker(boost::json::object const& request, ripple::uint256& marker);
+
+Status
+getAccount(boost::json::object const& request, ripple::AccountID& accountId);
+
+Status
+getAccount(
+    boost::json::object const& request,
+    ripple::AccountID& destAccount,
+    boost::string_view const& field);
+
+Status
+getOptionalAccount(
+    boost::json::object const& request,
+    std::optional<ripple::AccountID>& account,
+    boost::string_view const& field);
+
+Status
+getTaker(boost::json::object const& request, ripple::AccountID& takerID);
+
+Status
+getChannelId(boost::json::object const& request, ripple::uint256& channelId);
+
+bool
+specifiesCurrentOrClosedLedger(boost::json::object const& request);
+
 }  // namespace RPC
 #endif

src/rpc/WorkQueue.cpp

@@ -0,0 +1,11 @@
+#include <rpc/WorkQueue.h>
+
+WorkQueue::WorkQueue(std::uint32_t numWorkers, uint32_t maxSize)
+{
+    if (maxSize != 0)
+        maxSize_ = maxSize;
+    while (--numWorkers)
+    {
+        threads_.emplace_back([this] { ioc_.run(); });
+    }
+}

src/rpc/WorkQueue.h

@@ -0,0 +1,82 @@
+#ifndef CLIO_WORK_QUEUE_H
+#define CLIO_WORK_QUEUE_H
+
+#include <boost/asio.hpp>
+#include <boost/asio/spawn.hpp>
+#include <boost/json.hpp>
+#include <boost/log/trivial.hpp>
+
+#include <memory>
+#include <optional>
+#include <queue>
+#include <shared_mutex>
+#include <thread>
+
+class WorkQueue
+{
+    // these are cumulative for the lifetime of the process
+    std::atomic_uint64_t queued_ = 0;
+    std::atomic_uint64_t durationUs_ = 0;
+
+    std::atomic_uint64_t curSize_ = 0;
+    uint32_t maxSize_ = std::numeric_limits<uint32_t>::max();
+
+public:
+    WorkQueue(std::uint32_t numWorkers, uint32_t maxSize = 0);
+
+    template <typename F>
+    bool
+    postCoro(F&& f, bool isWhiteListed)
+    {
+        if (curSize_ >= maxSize_ && !isWhiteListed)
+        {
+            BOOST_LOG_TRIVIAL(warning)
+                << __func__
+                << " queue is full. rejecting job. current size = " << curSize_
+                << " max size = " << maxSize_;
+            return false;
+        }
+        ++curSize_;
+        auto start = std::chrono::system_clock::now();
+        // Each time we enqueue a job, we want to post a symmetrical job that
+        // will dequeue and run the job at the front of the job queue.
+        boost::asio::spawn(
+            ioc_,
+            [this, f = std::move(f), start](boost::asio::yield_context yield) {
+                auto run = std::chrono::system_clock::now();
+                auto wait =
+                    std::chrono::duration_cast<std::chrono::microseconds>(
+                        run - start)
+                        .count();
+                // increment queued_ here, in the same place we implement
+                // durationUs_
+                ++queued_;
+                durationUs_ += wait;
+                BOOST_LOG_TRIVIAL(debug) << "WorkQueue wait time = " << wait
+                                         << " queue size = " << curSize_;
+                f(yield);
+                --curSize_;
+            });
+        return true;
+    }
+
+    // TODO: this is not actually being called. Wait for application refactor
+    boost::json::object
+    report()
+    {
+        boost::json::object obj;
+        obj["queued"] = queued_;
+        obj["queued_duration_us"] = durationUs_;
+        obj["current_queue_size"] = curSize_;
+        obj["max_queue_size"] = maxSize_;
+        return obj;
+    }
+
+private:
+    std::vector<std::thread> threads_ = {};
+
+    boost::asio::io_context ioc_ = {};
+    std::optional<boost::asio::io_context::work> work_{ioc_};
+};
+
+#endif  // CLIO_WORK_QUEUE_H

src/rpc/handlers/AccountChannels.cpp

@@ -17,27 +17,27 @@ void
 addChannel(boost::json::array& jsonLines, ripple::SLE const& line)
 {
     boost::json::object jDst;
-    jDst["channel_id"] = ripple::to_string(line.key());
-    jDst["account"] = ripple::to_string(line.getAccountID(ripple::sfAccount));
-    jDst["destination_account"] =
+    jDst[JS(channel_id)] = ripple::to_string(line.key());
+    jDst[JS(account)] = ripple::to_string(line.getAccountID(ripple::sfAccount));
+    jDst[JS(destination_account)] =
         ripple::to_string(line.getAccountID(ripple::sfDestination));
-    jDst["amount"] = line[ripple::sfAmount].getText();
-    jDst["balance"] = line[ripple::sfBalance].getText();
+    jDst[JS(amount)] = line[ripple::sfAmount].getText();
+    jDst[JS(balance)] = line[ripple::sfBalance].getText();
     if (publicKeyType(line[ripple::sfPublicKey]))
     {
         ripple::PublicKey const pk(line[ripple::sfPublicKey]);
-        jDst["public_key"] = toBase58(ripple::TokenType::AccountPublic, pk);
-        jDst["public_key_hex"] = strHex(pk);
+        jDst[JS(public_key)] = toBase58(ripple::TokenType::AccountPublic, pk);
+        jDst[JS(public_key_hex)] = strHex(pk);
     }
-    jDst["settle_delay"] = line[ripple::sfSettleDelay];
+    jDst[JS(settle_delay)] = line[ripple::sfSettleDelay];
     if (auto const& v = line[~ripple::sfExpiration])
-        jDst["expiration"] = *v;
+        jDst[JS(expiration)] = *v;
     if (auto const& v = line[~ripple::sfCancelAfter])
-        jDst["cancel_after"] = *v;
+        jDst[JS(cancel_after)] = *v;
     if (auto const& v = line[~ripple::sfSourceTag])
-        jDst["source_tag"] = *v;
+        jDst[JS(source_tag)] = *v;
     if (auto const& v = line[~ripple::sfDestinationTag])
-        jDst["destination_tag"] = *v;
+        jDst[JS(destination_tag)] = *v;
 
     jsonLines.push_back(jDst);
 }
@@ -54,66 +54,45 @@ doAccountChannels(Context const& context)
 
     auto lgrInfo = std::get<ripple::LedgerInfo>(v);
 
-    if (!request.contains("account"))
-        return Status{Error::rpcINVALID_PARAMS, "missingAccount"};
+    ripple::AccountID accountID;
+    if (auto const status = getAccount(request, accountID); status)
+        return status;
 
-    if (!request.at("account").is_string())
-        return Status{Error::rpcINVALID_PARAMS, "accountNotString"};
+    auto rawAcct = context.backend->fetchLedgerObject(
+        ripple::keylet::account(accountID).key, lgrInfo.seq, context.yield);
 
-    auto accountID =
-        accountFromStringStrict(request.at("account").as_string().c_str());
+    if (!rawAcct)
+        return Status{Error::rpcACT_NOT_FOUND, "accountNotFound"};
 
-    if (!accountID)
-        return Status{Error::rpcINVALID_PARAMS, "malformedAccount"};
+    ripple::AccountID destAccount;
+    if (auto const status =
+            getAccount(request, destAccount, JS(destination_account));
+        status)
+        return status;
 
-    std::optional<ripple::AccountID> destAccount = {};
-    if (request.contains("destination_account"))
-    {
-        if (!request.at("destination_account").is_string())
-            return Status{Error::rpcINVALID_PARAMS, "destinationNotString"};
-
-        destAccount = accountFromStringStrict(
-            request.at("destination_account").as_string().c_str());
-
-        if (!destAccount)
-            return Status{Error::rpcINVALID_PARAMS, "destinationMalformed"};
-    }
-
-    std::uint32_t limit = 200;
-    if (request.contains("limit"))
-    {
-        if (!request.at("limit").is_int64())
-            return Status{Error::rpcINVALID_PARAMS, "limitNotInt"};
-
-        limit = request.at("limit").as_int64();
-        if (limit <= 0)
-            return Status{Error::rpcINVALID_PARAMS, "limitNotPositive"};
-    }
+    std::uint32_t limit;
+    if (auto const status = getLimit(context, limit); status)
+        return status;
 
     std::optional<std::string> marker = {};
-    if (request.contains("marker"))
+    if (request.contains(JS(marker)))
     {
-        if (!request.at("marker").is_string())
+        if (!request.at(JS(marker)).is_string())
             return Status{Error::rpcINVALID_PARAMS, "markerNotString"};
 
-        marker = request.at("marker").as_string().c_str();
+        marker = request.at(JS(marker)).as_string().c_str();
     }
 
-    response["account"] = ripple::to_string(*accountID);
-    response["channels"] = boost::json::value(boost::json::array_kind);
-    boost::json::array& jsonChannels = response.at("channels").as_array();
+    response[JS(account)] = ripple::to_string(accountID);
+    response[JS(channels)] = boost::json::value(boost::json::array_kind);
+    boost::json::array& jsonChannels = response.at(JS(channels)).as_array();
 
     auto const addToResponse = [&](ripple::SLE const& sle) {
         if (sle.getType() == ripple::ltPAYCHAN &&
-            sle.getAccountID(ripple::sfAccount) == *accountID &&
+            sle.getAccountID(ripple::sfAccount) == accountID &&
             (!destAccount ||
-             *destAccount == sle.getAccountID(ripple::sfDestination)))
+             destAccount == sle.getAccountID(ripple::sfDestination)))
         {
-            if (limit-- == 0)
-            {
-                return false;
-            }
-
             addChannel(jsonChannels, sle);
         }
 
@@ -122,23 +101,23 @@ doAccountChannels(Context const& context)
 
     auto next = traverseOwnedNodes(
         *context.backend,
-        *accountID,
+        accountID,
         lgrInfo.seq,
         limit,
         marker,
         context.yield,
         addToResponse);
 
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-    response["ledger_index"] = lgrInfo.seq;
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+    response[JS(ledger_index)] = lgrInfo.seq;
 
     if (auto status = std::get_if<RPC::Status>(&next))
         return *status;
 
-    auto nextCursor = std::get<RPC::AccountCursor>(next);
+    auto nextMarker = std::get<RPC::AccountCursor>(next);
 
-    if (nextCursor.isNonZero())
-        response["marker"] = nextCursor.toString();
+    if (nextMarker.isNonZero())
+        response[JS(marker)] = nextMarker.toString();
 
     return response;
 }

src/rpc/handlers/AccountCurrencies.cpp

@@ -24,17 +24,15 @@ doAccountCurrencies(Context const& context)
 
     auto lgrInfo = std::get<ripple::LedgerInfo>(v);
 
-    if (!request.contains("account"))
-        return Status{Error::rpcINVALID_PARAMS, "missingAccount"};
+    ripple::AccountID accountID;
+    if (auto const status = getAccount(request, accountID); status)
+        return status;
 
-    if (!request.at("account").is_string())
-        return Status{Error::rpcINVALID_PARAMS, "accountNotString"};
+    auto rawAcct = context.backend->fetchLedgerObject(
+        ripple::keylet::account(accountID).key, lgrInfo.seq, context.yield);
 
-    auto accountID =
-        accountFromStringStrict(request.at("account").as_string().c_str());
-
-    if (!accountID)
-        return Status{Error::rpcINVALID_PARAMS, "malformedAccount"};
+    if (!rawAcct)
+        return Status{Error::rpcACT_NOT_FOUND, "accountNotFound"};
 
     std::set<std::string> send, receive;
     auto const addToResponse = [&](ripple::SLE const& sle) {
@@ -61,26 +59,26 @@ doAccountCurrencies(Context const& context)
 
     traverseOwnedNodes(
         *context.backend,
-        *accountID,
+        accountID,
         lgrInfo.seq,
         std::numeric_limits<std::uint32_t>::max(),
         {},
         context.yield,
         addToResponse);
 
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-    response["ledger_index"] = lgrInfo.seq;
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+    response[JS(ledger_index)] = lgrInfo.seq;
 
-    response["receive_currencies"] =
+    response[JS(receive_currencies)] =
         boost::json::value(boost::json::array_kind);
     boost::json::array& jsonReceive =
-        response.at("receive_currencies").as_array();
+        response.at(JS(receive_currencies)).as_array();
 
     for (auto const& currency : receive)
         jsonReceive.push_back(currency.c_str());
 
-    response["send_currencies"] = boost::json::value(boost::json::array_kind);
-    boost::json::array& jsonSend = response.at("send_currencies").as_array();
+    response[JS(send_currencies)] = boost::json::value(boost::json::array_kind);
+    boost::json::array& jsonSend = response.at(JS(send_currencies)).as_array();
 
     for (auto const& currency : send)
         jsonSend.push_back(currency.c_str());

src/rpc/handlers/AccountInfo.cpp

@@ -29,10 +29,10 @@ doAccountInfo(Context const& context)
     boost::json::object response = {};
 
     std::string strIdent;
-    if (request.contains("account"))
-        strIdent = request.at("account").as_string().c_str();
-    else if (request.contains("ident"))
-        strIdent = request.at("ident").as_string().c_str();
+    if (request.contains(JS(account)))
+        strIdent = request.at(JS(account)).as_string().c_str();
+    else if (request.contains(JS(ident)))
+        strIdent = request.at(JS(ident)).as_string().c_str();
     else
         return Status{Error::rpcACT_MALFORMED};
 
@@ -54,10 +54,8 @@ doAccountInfo(Context const& context)
 
     auto key = ripple::keylet::account(accountID.value());
 
-    auto start = std::chrono::system_clock::now();
     std::optional<std::vector<unsigned char>> dbResponse =
         context.backend->fetchLedgerObject(key.key, lgrInfo.seq, context.yield);
-    auto end = std::chrono::system_clock::now();
 
     if (!dbResponse)
     {
@@ -71,18 +69,18 @@ doAccountInfo(Context const& context)
         return Status{Error::rpcDB_DESERIALIZATION};
 
     // if (!binary)
-    //     response["account_data"] = getJson(sle);
+    //     response[JS(account_data)] = getJson(sle);
     // else
-    //     response["account_data"] = ripple::strHex(*dbResponse);
-    // response["db_time"] = time;
+    //     response[JS(account_data)] = ripple::strHex(*dbResponse);
+    // response[JS(db_time)] = time;
 
-    response["account_data"] = toJson(sle);
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-    response["ledger_index"] = lgrInfo.seq;
+    response[JS(account_data)] = toJson(sle);
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+    response[JS(ledger_index)] = lgrInfo.seq;
 
     // Return SignerList(s) if that is requested.
-    if (request.contains("signer_lists") &&
-        request.at("signer_lists").as_bool())
+    if (request.contains(JS(signer_lists)) &&
+        request.at(JS(signer_lists)).as_bool())
     {
         // We put the SignerList in an array because of an anticipated
         // future when we support multiple signer lists on one account.
@@ -104,7 +102,7 @@ doAccountInfo(Context const& context)
             signerList.push_back(toJson(sleSigners));
         }
 
-        response["account_data"].as_object()["signer_lists"] =
+        response[JS(account_data)].as_object()[JS(signer_lists)] =
             std::move(signerList);
     }
 

src/rpc/handlers/AccountLines.cpp

@@ -39,7 +39,7 @@ addLine(
     auto lineQualityIn = viewLowest ? lowQualityIn : highQualityIn;
     auto lineQualityOut = viewLowest ? lowQualityOut : highQualityOut;
 
-    if (peerAccount and peerAccount != lineAccountIDPeer)
+    if (peerAccount && peerAccount != lineAccountIDPeer)
         return;
 
     if (!viewLowest)
@@ -64,25 +64,25 @@ addLine(
     ripple::STAmount const& saLimitPeer(lineLimitPeer);
 
     boost::json::object jPeer;
-    jPeer["account"] = ripple::to_string(lineAccountIDPeer);
-    jPeer["balance"] = saBalance.getText();
-    jPeer["currency"] = ripple::to_string(saBalance.issue().currency);
-    jPeer["limit"] = saLimit.getText();
-    jPeer["limit_peer"] = saLimitPeer.getText();
-    jPeer["quality_in"] = lineQualityIn;
-    jPeer["quality_out"] = lineQualityOut;
+    jPeer[JS(account)] = ripple::to_string(lineAccountIDPeer);
+    jPeer[JS(balance)] = saBalance.getText();
+    jPeer[JS(currency)] = ripple::to_string(saBalance.issue().currency);
+    jPeer[JS(limit)] = saLimit.getText();
+    jPeer[JS(limit_peer)] = saLimitPeer.getText();
+    jPeer[JS(quality_in)] = lineQualityIn;
+    jPeer[JS(quality_out)] = lineQualityOut;
     if (lineAuth)
-        jPeer["authorized"] = true;
+        jPeer[JS(authorized)] = true;
     if (lineAuthPeer)
-        jPeer["peer_authorized"] = true;
+        jPeer[JS(peer_authorized)] = true;
     if (lineNoRipple || !lineDefaultRipple)
-        jPeer["no_ripple"] = lineNoRipple;
+        jPeer[JS(no_ripple)] = lineNoRipple;
     if (lineNoRipple || !lineDefaultRipple)
-        jPeer["no_ripple_peer"] = lineNoRipplePeer;
+        jPeer[JS(no_ripple_peer)] = lineNoRipplePeer;
     if (lineFreeze)
-        jPeer["freeze"] = true;
+        jPeer[JS(freeze)] = true;
     if (lineFreezePeer)
-        jPeer["freeze_peer"] = true;
+        jPeer[JS(freeze_peer)] = true;
 
     jsonLines.push_back(jPeer);
 }
@@ -99,82 +99,65 @@ doAccountLines(Context const& context)
 
     auto lgrInfo = std::get<ripple::LedgerInfo>(v);
 
-    if (!request.contains("account"))
-        return Status{Error::rpcINVALID_PARAMS, "missingAccount"};
+    ripple::AccountID accountID;
+    if (auto const status = getAccount(request, accountID); status)
+        return status;
 
-    if (!request.at("account").is_string())
-        return Status{Error::rpcINVALID_PARAMS, "accountNotString"};
+    auto rawAcct = context.backend->fetchLedgerObject(
+        ripple::keylet::account(accountID).key, lgrInfo.seq, context.yield);
 
-    auto accountID =
-        accountFromStringStrict(request.at("account").as_string().c_str());
-
-    if (!accountID)
-        return Status{Error::rpcINVALID_PARAMS, "malformedAccount"};
+    if (!rawAcct)
+        return Status{Error::rpcACT_NOT_FOUND, "accountNotFound"};
 
     std::optional<ripple::AccountID> peerAccount;
-    if (request.contains("peer"))
+    if (auto const status = getOptionalAccount(request, peerAccount, JS(peer));
+        status)
+        return status;
+
+    std::uint32_t limit;
+    if (auto const status = getLimit(context, limit); status)
+        return status;
+
+    std::optional<std::string> marker = {};
+    if (request.contains(JS(marker)))
     {
-        if (!request.at("peer").is_string())
-            return Status{Error::rpcINVALID_PARAMS, "peerNotString"};
-
-        peerAccount =
-            accountFromStringStrict(request.at("peer").as_string().c_str());
-
-        if (!peerAccount)
-            return Status{Error::rpcINVALID_PARAMS, "peerMalformed"};
-    }
-
-    std::uint32_t limit = 200;
-    if (request.contains("limit"))
-    {
-        if (!request.at("limit").is_int64())
-            return Status{Error::rpcINVALID_PARAMS, "limitNotInt"};
-
-        limit = request.at("limit").as_int64();
-        if (limit <= 0)
-            return Status{Error::rpcINVALID_PARAMS, "limitNotPositive"};
-    }
-
-    std::optional<std::string> cursor = {};
-    if (request.contains("marker"))
-    {
-        if (!request.at("marker").is_string())
+        if (!request.at(JS(marker)).is_string())
             return Status{Error::rpcINVALID_PARAMS, "markerNotString"};
 
-        cursor = request.at("marker").as_string().c_str();
+        marker = request.at(JS(marker)).as_string().c_str();
     }
 
-    response["account"] = ripple::to_string(*accountID);
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-    response["ledger_index"] = lgrInfo.seq;
-    response["lines"] = boost::json::value(boost::json::array_kind);
-    boost::json::array& jsonLines = response.at("lines").as_array();
+    response[JS(account)] = ripple::to_string(accountID);
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+    response[JS(ledger_index)] = lgrInfo.seq;
+    response[JS(lines)] = boost::json::value(boost::json::array_kind);
+    boost::json::array& jsonLines = response.at(JS(lines)).as_array();
 
     auto const addToResponse = [&](ripple::SLE const& sle) -> void {
         if (sle.getType() == ripple::ltRIPPLE_STATE)
         {
-            addLine(jsonLines, sle, *accountID, peerAccount);
+            addLine(jsonLines, sle, accountID, peerAccount);
         }
     };
 
     auto next = traverseOwnedNodes(
         *context.backend,
-        *accountID,
+        accountID,
         lgrInfo.seq,
         limit,
-        cursor,
+        marker,
         context.yield,
         addToResponse);
 
     if (auto status = std::get_if<RPC::Status>(&next))
         return *status;
 
-    auto nextCursor = std::get<RPC::AccountCursor>(next);
+    auto nextMarker = std::get<RPC::AccountCursor>(next);
 
-    if (nextCursor.isNonZero())
-        response["marker"] = nextCursor.toString();
+    if (nextMarker.isNonZero())
+        response[JS(marker)] = nextMarker.toString();
 
     return response;
 }
 
-}  // namespace RPC
+}  // namespace RPC

src/rpc/handlers/AccountObjects.cpp

@@ -1,10 +1,12 @@
 #include <ripple/app/ledger/Ledger.h>
 #include <ripple/app/paths/TrustLine.h>
+#include <ripple/app/tx/impl/details/NFTokenUtils.h>
 #include <ripple/basics/StringUtilities.h>
 #include <ripple/protocol/ErrorCodes.h>
 #include <ripple/protocol/Indexes.h>
 #include <ripple/protocol/STLedgerEntry.h>
 #include <ripple/protocol/jss.h>
+#include <ripple/protocol/nftPageMask.h>
 #include <boost/json.hpp>
 #include <algorithm>
 #include <rpc/RPCHelpers.h>
@@ -23,7 +25,112 @@ std::unordered_map<std::string, ripple::LedgerEntryType> types{
     {"escrow", ripple::ltESCROW},
     {"deposit_preauth", ripple::ltDEPOSIT_PREAUTH},
     {"check", ripple::ltCHECK},
-};
+    {"nft_page", ripple::ltNFTOKEN_PAGE},
+    {"nft_offer", ripple::ltNFTOKEN_OFFER}};
+
+Result
+doAccountNFTs(Context const& context)
+{
+    auto request = context.params;
+    boost::json::object response = {};
+
+    auto v = ledgerInfoFromRequest(context);
+    if (auto status = std::get_if<Status>(&v))
+        return *status;
+
+    auto lgrInfo = std::get<ripple::LedgerInfo>(v);
+
+    ripple::AccountID accountID;
+    if (auto const status = getAccount(request, accountID); status)
+        return status;
+
+    if (!accountID)
+        return Status{Error::rpcINVALID_PARAMS, "malformedAccount"};
+
+    auto rawAcct = context.backend->fetchLedgerObject(
+        ripple::keylet::account(accountID).key, lgrInfo.seq, context.yield);
+
+    if (!rawAcct)
+        return Status{Error::rpcACT_NOT_FOUND, "accountNotFound"};
+
+    std::uint32_t limit;
+    if (auto const status = getLimit(context, limit); status)
+        return status;
+
+    ripple::uint256 marker;
+    if (auto const status = getHexMarker(request, marker); status)
+        return status;
+
+    response[JS(account)] = ripple::toBase58(accountID);
+    response[JS(validated)] = true;
+
+    std::uint32_t numPages = 0;
+    response[JS(account_nfts)] = boost::json::value(boost::json::array_kind);
+    auto& nfts = response.at(JS(account_nfts)).as_array();
+
+    // if a marker was passed, start at the page specified in marker. Else,
+    // start at the max page
+    auto const pageKey =
+        marker.isZero() ? ripple::keylet::nftpage_max(accountID).key : marker;
+
+    auto const blob =
+        context.backend->fetchLedgerObject(pageKey, lgrInfo.seq, context.yield);
+    if (!blob)
+        return response;
+    std::optional<ripple::SLE const> page{
+        ripple::SLE{ripple::SerialIter{blob->data(), blob->size()}, pageKey}};
+
+    // Continue iteration from the current page
+    while (page)
+    {
+        auto arr = page->getFieldArray(ripple::sfNFTokens);
+
+        for (auto const& o : arr)
+        {
+            ripple::uint256 const nftokenID = o[ripple::sfNFTokenID];
+
+            {
+                nfts.push_back(
+                    toBoostJson(o.getJson(ripple::JsonOptions::none)));
+                auto& obj = nfts.back().as_object();
+
+                // Pull out the components of the nft ID.
+                obj[SFS(sfFlags)] = ripple::nft::getFlags(nftokenID);
+                obj[SFS(sfIssuer)] =
+                    to_string(ripple::nft::getIssuer(nftokenID));
+                obj[SFS(sfNFTokenTaxon)] =
+                    ripple::nft::toUInt32(ripple::nft::getTaxon(nftokenID));
+                obj[JS(nft_serial)] = ripple::nft::getSerial(nftokenID);
+
+                if (std::uint16_t xferFee = {
+                        ripple::nft::getTransferFee(nftokenID)})
+                    obj[SFS(sfTransferFee)] = xferFee;
+            }
+        }
+
+        ++numPages;
+        if (auto npm = (*page)[~ripple::sfPreviousPageMin])
+        {
+            auto const nextKey = ripple::Keylet(ripple::ltNFTOKEN_PAGE, *npm);
+            if (numPages == limit)
+            {
+                response[JS(marker)] = to_string(nextKey.key);
+                response[JS(limit)] = numPages;
+                return response;
+            }
+            auto const nextBlob = context.backend->fetchLedgerObject(
+                nextKey.key, lgrInfo.seq, context.yield);
+
+            page.emplace(ripple::SLE{
+                ripple::SerialIter{nextBlob->data(), nextBlob->size()},
+                nextKey.key});
+        }
+        else
+            page.reset();
+    }
+
+    return response;
+}
 
 Result
 doAccountObjects(Context const& context)
@@ -37,54 +144,40 @@ doAccountObjects(Context const& context)
 
     auto lgrInfo = std::get<ripple::LedgerInfo>(v);
 
-    if (!request.contains("account"))
-        return Status{Error::rpcINVALID_PARAMS, "missingAccount"};
+    ripple::AccountID accountID;
+    if (auto const status = getAccount(request, accountID); status)
+        return status;
 
-    if (!request.at("account").is_string())
-        return Status{Error::rpcINVALID_PARAMS, "accountNotString"};
+    std::uint32_t limit;
+    if (auto const status = getLimit(context, limit); status)
+        return status;
 
-    auto accountID =
-        accountFromStringStrict(request.at("account").as_string().c_str());
-
-    if (!accountID)
-        return Status{Error::rpcINVALID_PARAMS, "malformedAccount"};
-
-    std::uint32_t limit = 200;
-    if (request.contains("limit"))
-    {
-        if (!request.at("limit").is_int64())
-            return Status{Error::rpcINVALID_PARAMS, "limitNotInt"};
-
-        limit = request.at("limit").as_int64();
-        if (limit <= 0)
-            return Status{Error::rpcINVALID_PARAMS, "limitNotPositive"};
-    }
-
-    std::optional<std::string> cursor = {};
+    std::optional<std::string> marker = {};
     if (request.contains("marker"))
     {
         if (!request.at("marker").is_string())
             return Status{Error::rpcINVALID_PARAMS, "markerNotString"};
 
-        cursor = request.at("marker").as_string().c_str();
+        marker = request.at("marker").as_string().c_str();
     }
 
     std::optional<ripple::LedgerEntryType> objectType = {};
-    if (request.contains("type"))
+    if (request.contains(JS(type)))
     {
-        if (!request.at("type").is_string())
+        if (!request.at(JS(type)).is_string())
             return Status{Error::rpcINVALID_PARAMS, "typeNotString"};
 
-        std::string typeAsString = request.at("type").as_string().c_str();
+        std::string typeAsString = request.at(JS(type)).as_string().c_str();
         if (types.find(typeAsString) == types.end())
             return Status{Error::rpcINVALID_PARAMS, "typeInvalid"};
 
         objectType = types[typeAsString];
     }
 
-    response["account"] = ripple::to_string(*accountID);
-    response["account_objects"] = boost::json::value(boost::json::array_kind);
-    boost::json::array& jsonObjects = response.at("account_objects").as_array();
+    response[JS(account)] = ripple::to_string(accountID);
+    response[JS(account_objects)] = boost::json::value(boost::json::array_kind);
+    boost::json::array& jsonObjects =
+        response.at(JS(account_objects)).as_array();
 
     auto const addToResponse = [&](ripple::SLE const& sle) {
         if (!objectType || objectType == sle.getType())
@@ -95,23 +188,23 @@ doAccountObjects(Context const& context)
 
     auto next = traverseOwnedNodes(
         *context.backend,
-        *accountID,
+        accountID,
         lgrInfo.seq,
         limit,
-        cursor,
+        marker,
         context.yield,
         addToResponse);
 
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-    response["ledger_index"] = lgrInfo.seq;
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+    response[JS(ledger_index)] = lgrInfo.seq;
 
     if (auto status = std::get_if<RPC::Status>(&next))
         return *status;
 
-    auto nextCursor = std::get<RPC::AccountCursor>(next);
+    auto nextMarker = std::get<RPC::AccountCursor>(next);
 
-    if (nextCursor.isNonZero())
-        response["marker"] = nextCursor.toString();
+    if (nextMarker.isNonZero())
+        response[JS(marker)] = nextMarker.toString();
 
     return response;
 }

src/rpc/handlers/AccountOffers.cpp

@@ -27,37 +27,39 @@ addOffer(boost::json::array& offersJson, ripple::SLE const& offer)
 
     if (!takerPays.native())
     {
-        obj["taker_pays"] = boost::json::value(boost::json::object_kind);
-        boost::json::object& takerPaysJson = obj.at("taker_pays").as_object();
+        obj[JS(taker_pays)] = boost::json::value(boost::json::object_kind);
+        boost::json::object& takerPaysJson = obj.at(JS(taker_pays)).as_object();
 
-        takerPaysJson["value"] = takerPays.getText();
-        takerPaysJson["currency"] = ripple::to_string(takerPays.getCurrency());
-        takerPaysJson["issuer"] = ripple::to_string(takerPays.getIssuer());
+        takerPaysJson[JS(value)] = takerPays.getText();
+        takerPaysJson[JS(currency)] =
+            ripple::to_string(takerPays.getCurrency());
+        takerPaysJson[JS(issuer)] = ripple::to_string(takerPays.getIssuer());
     }
     else
     {
-        obj["taker_pays"] = takerPays.getText();
+        obj[JS(taker_pays)] = takerPays.getText();
     }
 
     if (!takerGets.native())
     {
-        obj["taker_gets"] = boost::json::value(boost::json::object_kind);
-        boost::json::object& takerGetsJson = obj.at("taker_gets").as_object();
+        obj[JS(taker_gets)] = boost::json::value(boost::json::object_kind);
+        boost::json::object& takerGetsJson = obj.at(JS(taker_gets)).as_object();
 
-        takerGetsJson["value"] = takerGets.getText();
-        takerGetsJson["currency"] = ripple::to_string(takerGets.getCurrency());
-        takerGetsJson["issuer"] = ripple::to_string(takerGets.getIssuer());
+        takerGetsJson[JS(value)] = takerGets.getText();
+        takerGetsJson[JS(currency)] =
+            ripple::to_string(takerGets.getCurrency());
+        takerGetsJson[JS(issuer)] = ripple::to_string(takerGets.getIssuer());
     }
     else
     {
-        obj["taker_gets"] = takerGets.getText();
+        obj[JS(taker_gets)] = takerGets.getText();
     }
 
-    obj["seq"] = offer.getFieldU32(ripple::sfSequence);
-    obj["flags"] = offer.getFieldU32(ripple::sfFlags);
-    obj["quality"] = rate.getText();
+    obj[JS(seq)] = offer.getFieldU32(ripple::sfSequence);
+    obj[JS(flags)] = offer.getFieldU32(ripple::sfFlags);
+    obj[JS(quality)] = rate.getText();
     if (offer.isFieldPresent(ripple::sfExpiration))
-        obj["expiration"] = offer.getFieldU32(ripple::sfExpiration);
+        obj[JS(expiration)] = offer.getFieldU32(ripple::sfExpiration);
 
     offersJson.push_back(obj);
 };
@@ -74,52 +76,38 @@ doAccountOffers(Context const& context)
 
     auto lgrInfo = std::get<ripple::LedgerInfo>(v);
 
-    if (!request.contains("account"))
-        return Status{Error::rpcINVALID_PARAMS, "missingAccount"};
+    ripple::AccountID accountID;
+    if (auto const status = getAccount(request, accountID); status)
+        return status;
 
-    if (!request.at("account").is_string())
-        return Status{Error::rpcINVALID_PARAMS, "accountNotString"};
+    auto rawAcct = context.backend->fetchLedgerObject(
+        ripple::keylet::account(accountID).key, lgrInfo.seq, context.yield);
 
-    auto accountID =
-        accountFromStringStrict(request.at("account").as_string().c_str());
+    if (!rawAcct)
+        return Status{Error::rpcACT_NOT_FOUND, "accountNotFound"};
 
-    if (!accountID)
-        return Status{Error::rpcINVALID_PARAMS, "malformedAccount"};
+    std::uint32_t limit;
+    if (auto const status = getLimit(context, limit); status)
+        return status;
 
-    std::uint32_t limit = 200;
-    if (request.contains("limit"))
+    std::optional<std::string> marker = {};
+    if (request.contains(JS(marker)))
     {
-        if (!request.at("limit").is_int64())
-            return Status{Error::rpcINVALID_PARAMS, "limitNotInt"};
-
-        limit = request.at("limit").as_int64();
-        if (limit <= 0)
-            return Status{Error::rpcINVALID_PARAMS, "limitNotPositive"};
-    }
-
-    std::optional<std::string> cursor = {};
-    if (request.contains("marker"))
-    {
-        if (!request.at("marker").is_string())
+        if (!request.at(JS(marker)).is_string())
             return Status{Error::rpcINVALID_PARAMS, "markerNotString"};
 
-        cursor = request.at("marker").as_string().c_str();
+        marker = request.at(JS(marker)).as_string().c_str();
     }
 
-    response["account"] = ripple::to_string(*accountID);
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-    response["ledger_index"] = lgrInfo.seq;
-    response["offers"] = boost::json::value(boost::json::array_kind);
-    boost::json::array& jsonLines = response.at("offers").as_array();
+    response[JS(account)] = ripple::to_string(accountID);
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+    response[JS(ledger_index)] = lgrInfo.seq;
+    response[JS(offers)] = boost::json::value(boost::json::array_kind);
+    boost::json::array& jsonLines = response.at(JS(offers)).as_array();
 
     auto const addToResponse = [&](ripple::SLE const& sle) {
         if (sle.getType() == ripple::ltOFFER)
         {
-            if (limit-- == 0)
-            {
-                return false;
-            }
-
             addOffer(jsonLines, sle);
         }
 
@@ -128,22 +116,22 @@ doAccountOffers(Context const& context)
 
     auto next = traverseOwnedNodes(
         *context.backend,
-        *accountID,
+        accountID,
         lgrInfo.seq,
         limit,
-        cursor,
+        marker,
         context.yield,
         addToResponse);
 
     if (auto status = std::get_if<RPC::Status>(&next))
         return *status;
 
-    auto nextCursor = std::get<RPC::AccountCursor>(next);
+    auto nextMarker = std::get<RPC::AccountCursor>(next);
 
-    if (nextCursor.isNonZero())
-        response["marker"] = nextCursor.toString();
+    if (nextMarker.isNonZero())
+        response[JS(marker)] = nextMarker.toString();
 
     return response;
 }
 
-}  // namespace RPC
+}  // namespace RPC

src/rpc/handlers/AccountTx.cpp

@@ -12,60 +12,38 @@ doAccountTx(Context const& context)
     auto request = context.params;
     boost::json::object response = {};
 
-    if (!request.contains("account"))
-        return Status{Error::rpcINVALID_PARAMS, "missingAccount"};
+    ripple::AccountID accountID;
+    if (auto const status = getAccount(request, accountID); status)
+        return status;
 
-    if (!request.at("account").is_string())
-        return Status{Error::rpcINVALID_PARAMS, "accountNotString"};
+    bool const binary = getBool(request, JS(binary), false);
+    bool const forward = getBool(request, JS(forward), false);
 
-    auto accountID =
-        accountFromStringStrict(request.at("account").as_string().c_str());
+    std::optional<Backend::TransactionsCursor> cursor;
 
-    if (!accountID)
-        return Status{Error::rpcINVALID_PARAMS, "malformedAccount"};
-
-    bool binary = false;
-    if (request.contains("binary"))
+    if (request.contains(JS(marker)))
     {
-        if (!request.at("binary").is_bool())
-            return Status{Error::rpcINVALID_PARAMS, "binaryFlagNotBool"};
-
-        binary = request.at("binary").as_bool();
-    }
-    bool forward = false;
-    if (request.contains("forward"))
-    {
-        if (!request.at("forward").is_bool())
-            return Status{Error::rpcINVALID_PARAMS, "forwardNotBool"};
-
-        forward = request.at("forward").as_bool();
-    }
-
-    std::optional<Backend::AccountTransactionsCursor> cursor;
-
-    if (request.contains("marker"))
-    {
-        auto const& obj = request.at("marker").as_object();
+        auto const& obj = request.at(JS(marker)).as_object();
 
         std::optional<std::uint32_t> transactionIndex = {};
-        if (obj.contains("seq"))
+        if (obj.contains(JS(seq)))
         {
-            if (!obj.at("seq").is_int64())
+            if (!obj.at(JS(seq)).is_int64())
                 return Status{
                     Error::rpcINVALID_PARAMS, "transactionIndexNotInt"};
 
             transactionIndex =
-                boost::json::value_to<std::uint32_t>(obj.at("seq"));
+                boost::json::value_to<std::uint32_t>(obj.at(JS(seq)));
         }
 
         std::optional<std::uint32_t> ledgerIndex = {};
-        if (obj.contains("ledger"))
+        if (obj.contains(JS(ledger)))
         {
-            if (!obj.at("ledger").is_int64())
+            if (!obj.at(JS(ledger)).is_int64())
                 return Status{Error::rpcINVALID_PARAMS, "ledgerIndexNotInt"};
 
             ledgerIndex =
-                boost::json::value_to<std::uint32_t>(obj.at("ledger"));
+                boost::json::value_to<std::uint32_t>(obj.at(JS(ledger)));
         }
 
         if (!transactionIndex || !ledgerIndex)
@@ -75,9 +53,9 @@ doAccountTx(Context const& context)
     }
 
     auto minIndex = context.range.minSequence;
-    if (request.contains("ledger_index_min"))
+    if (request.contains(JS(ledger_index_min)))
     {
-        auto& min = request.at("ledger_index_min");
+        auto& min = request.at(JS(ledger_index_min));
 
         if (!min.is_int64())
             return Status{Error::rpcINVALID_PARAMS, "ledgerSeqMinNotNumber"};
@@ -87,7 +65,7 @@ doAccountTx(Context const& context)
             if (context.range.maxSequence < min.as_int64() ||
                 context.range.minSequence > min.as_int64())
                 return Status{
-                    Error::rpcINVALID_PARAMS, "ledgerSeqMaxOutOfRange"};
+                    Error::rpcINVALID_PARAMS, "ledgerSeqMinOutOfRange"};
             else
                 minIndex = value_to<std::uint32_t>(min);
         }
@@ -97,9 +75,9 @@ doAccountTx(Context const& context)
     }
 
     auto maxIndex = context.range.maxSequence;
-    if (request.contains("ledger_index_max"))
+    if (request.contains(JS(ledger_index_max)))
     {
-        auto& max = request.at("ledger_index_max");
+        auto& max = request.at(JS(ledger_index_max));
 
         if (!max.is_int64())
             return Status{Error::rpcINVALID_PARAMS, "ledgerSeqMaxNotNumber"};
@@ -121,30 +99,18 @@ doAccountTx(Context const& context)
             cursor = {maxIndex, INT32_MAX};
     }
 
-    if (request.contains("ledger_index"))
+    if (request.contains(JS(ledger_index)) || request.contains(JS(ledger_hash)))
     {
-        if (!request.at("ledger_index").is_int64())
-            return Status{Error::rpcINVALID_PARAMS, "ledgerIndexNotNumber"};
+        if (request.contains(JS(ledger_index_max)) ||
+            request.contains(JS(ledger_index_min)))
+            return Status{
+                Error::rpcINVALID_PARAMS, "containsLedgerSpecifierAndRange"};
 
-        auto ledgerIndex =
-            boost::json::value_to<std::uint32_t>(request.at("ledger_index"));
-        maxIndex = minIndex = ledgerIndex;
-    }
+        auto v = ledgerInfoFromRequest(context);
+        if (auto status = std::get_if<Status>(&v))
+            return *status;
 
-    if (request.contains("ledger_hash"))
-    {
-        if (!request.at("ledger_hash").is_string())
-            return RPC::Status{
-                RPC::Error::rpcINVALID_PARAMS, "ledgerHashNotString"};
-
-        ripple::uint256 ledgerHash;
-        if (!ledgerHash.parseHex(request.at("ledger_hash").as_string().c_str()))
-            return RPC::Status{
-                RPC::Error::rpcINVALID_PARAMS, "ledgerHashMalformed"};
-
-        auto lgrInfo =
-            context.backend->fetchLedgerByHash(ledgerHash, context.yield);
-        maxIndex = minIndex = lgrInfo->seq;
+        maxIndex = minIndex = std::get<ripple::LedgerInfo>(v).seq;
     }
 
     if (!cursor)
@@ -155,37 +121,31 @@ doAccountTx(Context const& context)
             cursor = {maxIndex, INT32_MAX};
     }
 
-    std::uint32_t limit = 200;
-    if (request.contains("limit"))
-    {
-        if (!request.at("limit").is_int64())
-            return Status{Error::rpcINVALID_PARAMS, "limitNotInt"};
+    std::uint32_t limit;
+    if (auto const status = getLimit(context, limit); status)
+        return status;
 
-        limit = request.at("limit").as_int64();
-        if (limit <= 0)
-            return Status{Error::rpcINVALID_PARAMS, "limitNotPositive"};
-
-        response["limit"] = limit;
-    }
+    if (request.contains(JS(limit)))
+        response[JS(limit)] = limit;
 
     boost::json::array txns;
     auto start = std::chrono::system_clock::now();
     auto [blobs, retCursor] = context.backend->fetchAccountTransactions(
-        *accountID, limit, forward, cursor, context.yield);
+        accountID, limit, forward, cursor, context.yield);
 
     auto end = std::chrono::system_clock::now();
     BOOST_LOG_TRIVIAL(info) << __func__ << " db fetch took "
                             << ((end - start).count() / 1000000000.0)
                             << " num blobs = " << blobs.size();
 
-    response["account"] = ripple::to_string(*accountID);
+    response[JS(account)] = ripple::to_string(accountID);
 
     if (retCursor)
     {
         boost::json::object cursorJson;
-        cursorJson["ledger"] = retCursor->ledgerSequence;
-        cursorJson["seq"] = retCursor->transactionIndex;
-        response["marker"] = cursorJson;
+        cursorJson[JS(ledger)] = retCursor->ledgerSequence;
+        cursorJson[JS(seq)] = retCursor->transactionIndex;
+        response[JS(marker)] = cursorJson;
     }
 
     std::optional<size_t> maxReturnedIndex;
@@ -206,18 +166,20 @@ doAccountTx(Context const& context)
         if (!binary)
         {
             auto [txn, meta] = toExpandedJson(txnPlusMeta);
-            obj["meta"] = meta;
-            obj["tx"] = txn;
-            obj["tx"].as_object()["ledger_index"] = txnPlusMeta.ledgerSequence;
-            obj["tx"].as_object()["date"] = txnPlusMeta.date;
+            obj[JS(meta)] = meta;
+            obj[JS(tx)] = txn;
+            obj[JS(tx)].as_object()[JS(ledger_index)] =
+                txnPlusMeta.ledgerSequence;
+            obj[JS(tx)].as_object()[JS(date)] = txnPlusMeta.date;
         }
         else
         {
-            obj["meta"] = ripple::strHex(txnPlusMeta.metadata);
-            obj["tx_blob"] = ripple::strHex(txnPlusMeta.transaction);
-            obj["ledger_index"] = txnPlusMeta.ledgerSequence;
-            obj["date"] = txnPlusMeta.date;
+            obj[JS(meta)] = ripple::strHex(txnPlusMeta.metadata);
+            obj[JS(tx_blob)] = ripple::strHex(txnPlusMeta.transaction);
+            obj[JS(ledger_index)] = txnPlusMeta.ledgerSequence;
+            obj[JS(date)] = txnPlusMeta.date;
         }
+        obj[JS(validated)] = true;
 
         txns.push_back(obj);
         if (!minReturnedIndex || txnPlusMeta.ledgerSequence < *minReturnedIndex)
@@ -227,24 +189,18 @@ doAccountTx(Context const& context)
     }
 
     assert(cursor);
-    if (forward)
+    if (!forward)
     {
-        response["ledger_index_min"] = cursor->ledgerSequence;
-        if (blobs.size() >= limit)
-            response["ledger_index_max"] = *maxReturnedIndex;
-        else
-            response["ledger_index_max"] = maxIndex;
+        response[JS(ledger_index_min)] = cursor->ledgerSequence;
+        response[JS(ledger_index_max)] = maxIndex;
     }
     else
     {
-        response["ledger_index_max"] = cursor->ledgerSequence;
-        if (blobs.size() >= limit)
-            response["ledger_index_min"] = *minReturnedIndex;
-        else
-            response["ledger_index_min"] = minIndex;
+        response[JS(ledger_index_max)] = cursor->ledgerSequence;
+        response[JS(ledger_index_min)] = minIndex;
     }
 
-    response["transactions"] = txns;
+    response[JS(transactions)] = txns;
 
     auto end2 = std::chrono::system_clock::now();
     BOOST_LOG_TRIVIAL(info) << __func__ << " serialization took "

src/rpc/handlers/BookChanges.cpp

@@ -0,0 +1,250 @@
+#include <ripple/app/ledger/Ledger.h>
+#include <ripple/basics/ToString.h>
+
+#include <backend/BackendInterface.h>
+#include <rpc/RPCHelpers.h>
+
+#include <boost/json.hpp>
+#include <algorithm>
+
+namespace json = boost::json;
+using namespace ripple;
+
+namespace RPC {
+
+struct BookChange
+{
+    STAmount sideAVolume;
+    STAmount sideBVolume;
+    STAmount highRate;
+    STAmount lowRate;
+    STAmount openRate;
+    STAmount closeRate;
+};
+
+class BookChangesHandler
+{
+    std::reference_wrapper<Context const> context_;
+    std::map<std::string, BookChange> tally_ = {};
+    std::optional<uint32_t> offerCancel_ = {};
+
+public:
+    ~BookChangesHandler() = default;
+    explicit BookChangesHandler(Context const& context)
+        : context_{std::cref(context)}
+    {
+    }
+
+    BookChangesHandler(BookChangesHandler const&) = delete;
+    BookChangesHandler(BookChangesHandler&&) = delete;
+    BookChangesHandler&
+    operator=(BookChangesHandler const&) = delete;
+    BookChangesHandler&
+    operator=(BookChangesHandler&&) = delete;
+
+    /**
+     * @brief Handles the `book_change` request for given transactions
+     *
+     * @param transactions The transactions to compute changes for
+     * @return std::vector<BookChange> The changes
+     */
+    std::vector<BookChange>
+    handle(LedgerInfo const& ledger)
+    {
+        reset();
+
+        for (auto const transactions =
+                 context_.get().backend->fetchAllTransactionsInLedger(
+                     ledger.seq, context_.get().yield);
+             auto const& tx : transactions)
+        {
+            handleBookChange(tx);
+        }
+
+        // TODO: rewrite this with std::ranges when compilers catch up
+        std::vector<BookChange> changes;
+        std::transform(
+            std::make_move_iterator(std::begin(tally_)),
+            std::make_move_iterator(std::end(tally_)),
+            std::back_inserter(changes),
+            [](auto obj) { return obj.second; });
+        return changes;
+    }
+
+private:
+    inline void
+    reset() noexcept
+    {
+        tally_.clear();
+        offerCancel_ = std::nullopt;
+    }
+
+    void
+    handleAffectedNode(STObject const& node)
+    {
+        auto const& metaType = node.getFName();
+        auto const nodeType = node.getFieldU16(sfLedgerEntryType);
+
+        // we only care about ltOFFER objects being modified or
+        // deleted
+        if (nodeType != ltOFFER || metaType == sfCreatedNode)
+            return;
+
+        // if either FF or PF are missing we can't compute
+        // but generally these are cancelled rather than crossed
+        // so skipping them is consistent
+        if (!node.isFieldPresent(sfFinalFields) ||
+            !node.isFieldPresent(sfPreviousFields))
+            return;
+
+        auto const& finalFields =
+            node.peekAtField(sfFinalFields).downcast<STObject>();
+        auto const& previousFields =
+            node.peekAtField(sfPreviousFields).downcast<STObject>();
+
+        // defensive case that should never be hit
+        if (!finalFields.isFieldPresent(sfTakerGets) ||
+            !finalFields.isFieldPresent(sfTakerPays) ||
+            !previousFields.isFieldPresent(sfTakerGets) ||
+            !previousFields.isFieldPresent(sfTakerPays))
+            return;
+
+        // filter out any offers deleted by explicit offer cancels
+        if (metaType == sfDeletedNode && offerCancel_ &&
+            finalFields.getFieldU32(sfSequence) == *offerCancel_)
+            return;
+
+        // compute the difference in gets and pays actually
+        // affected onto the offer
+        auto const deltaGets = finalFields.getFieldAmount(sfTakerGets) -
+            previousFields.getFieldAmount(sfTakerGets);
+        auto const deltaPays = finalFields.getFieldAmount(sfTakerPays) -
+            previousFields.getFieldAmount(sfTakerPays);
+
+        auto const g = to_string(deltaGets.issue());
+        auto const p = to_string(deltaPays.issue());
+
+        auto const noswap =
+            isXRP(deltaGets) ? true : (isXRP(deltaPays) ? false : (g < p));
+
+        auto first = noswap ? deltaGets : deltaPays;
+        auto second = noswap ? deltaPays : deltaGets;
+
+        // defensively programmed, should (probably) never happen
+        if (second == beast::zero)
+            return;
+
+        auto const rate = divide(first, second, noIssue());
+
+        if (first < beast::zero)
+            first = -first;
+
+        if (second < beast::zero)
+            second = -second;
+
+        auto const key = noswap ? (g + '|' + p) : (p + '|' + g);
+        if (tally_.contains(key))
+        {
+            auto& entry = tally_.at(key);
+
+            entry.sideAVolume += first;
+            entry.sideBVolume += second;
+
+            if (entry.highRate < rate)
+                entry.highRate = rate;
+
+            if (entry.lowRate > rate)
+                entry.lowRate = rate;
+
+            entry.closeRate = rate;
+        }
+        else
+        {
+            // TODO: use paranthesized initialization when clang catches up
+            tally_[key] = {
+                first,   // sideAVolume
+                second,  // sideBVolume
+                rate,    // highRate
+                rate,    // lowRate
+                rate,    // openRate
+                rate,    // closeRate
+            };
+        }
+    }
+
+    void
+    handleBookChange(Backend::TransactionAndMetadata const& blob)
+    {
+        auto const [tx, meta] = deserializeTxPlusMeta(blob);
+        if (!tx || !meta || !tx->isFieldPresent(sfTransactionType))
+            return;
+
+        offerCancel_ = shouldCancelOffer(tx);
+        for (auto const& node : meta->getFieldArray(sfAffectedNodes))
+            handleAffectedNode(node);
+    }
+
+    std::optional<uint32_t>
+    shouldCancelOffer(std::shared_ptr<ripple::STTx const> const& tx) const
+    {
+        switch (tx->getFieldU16(sfTransactionType))
+        {
+            // in future if any other ways emerge to cancel an offer
+            // this switch makes them easy to add
+            case ttOFFER_CANCEL:
+            case ttOFFER_CREATE:
+                if (tx->isFieldPresent(sfOfferSequence))
+                    return tx->getFieldU32(sfOfferSequence);
+            default:
+                return std::nullopt;
+        }
+    }
+};
+
+void
+tag_invoke(
+    const json::value_from_tag&,
+    json::value& jv,
+    BookChange const& change)
+{
+    auto amountStr = [](STAmount const& amount) -> std::string {
+        return isXRP(amount) ? to_string(amount.xrp())
+                             : to_string(amount.iou());
+    };
+
+    auto currencyStr = [](STAmount const& amount) -> std::string {
+        return isXRP(amount) ? "XRP_drops" : to_string(amount.issue());
+    };
+
+    jv = {
+        {JS(currency_a), currencyStr(change.sideAVolume)},
+        {JS(currency_b), currencyStr(change.sideBVolume)},
+        {JS(volume_a), amountStr(change.sideAVolume)},
+        {JS(volume_b), amountStr(change.sideBVolume)},
+        {JS(high), to_string(change.highRate.iou())},
+        {JS(low), to_string(change.lowRate.iou())},
+        {JS(open), to_string(change.openRate.iou())},
+        {JS(close), to_string(change.closeRate.iou())},
+    };
+}
+
+Result
+doBookChanges(Context const& context)
+{
+    auto const request = context.params;
+    auto const info = ledgerInfoFromRequest(context);
+    if (auto const status = std::get_if<Status>(&info))
+        return *status;
+
+    auto const lgrInfo = std::get<ripple::LedgerInfo>(info);
+    auto const changes = BookChangesHandler{context}.handle(lgrInfo);
+    return json::object{
+        {JS(type), "bookChanges"},
+        {JS(ledger_index), lgrInfo.seq},
+        {JS(ledger_hash), to_string(lgrInfo.hash)},
+        {JS(ledger_time), lgrInfo.closeTime.time_since_epoch().count()},
+        {JS(changes), json::value_from(changes)},
+    };
+}
+
+}  // namespace RPC

src/rpc/handlers/BookOffers.cpp

@@ -48,42 +48,21 @@ doBookOffers(Context const& context)
         }
     }
 
-    std::uint32_t limit = 200;
-    if (request.contains("limit"))
-    {
-        if (!request.at("limit").is_int64())
-            return Status{Error::rpcINVALID_PARAMS, "limitNotInt"};
-
-        limit = request.at("limit").as_int64();
-        if (limit <= 0)
-            return Status{Error::rpcINVALID_PARAMS, "limitNotPositive"};
-    }
+    std::uint32_t limit;
+    if (auto const status = getLimit(context, limit); status)
+        return status;
 
     ripple::AccountID takerID = beast::zero;
-    if (request.contains("taker"))
-    {
-        auto parsed = parseTaker(request["taker"]);
-        if (auto status = std::get_if<Status>(&parsed))
-            return *status;
-        else
-        {
-            takerID = std::get<ripple::AccountID>(parsed);
-        }
-    }
+    if (auto const status = getTaker(request, takerID); status)
+        return status;
 
-    ripple::uint256 cursor = beast::zero;
-    if (request.contains("cursor"))
-    {
-        if (!request.at("cursor").is_string())
-            return Status{Error::rpcINVALID_PARAMS, "cursorNotString"};
-
-        if (!cursor.parseHex(request.at("cursor").as_string().c_str()))
-            return Status{Error::rpcINVALID_PARAMS, "malformedCursor"};
-    }
+    ripple::uint256 marker = beast::zero;
+    if (auto const status = getHexMarker(request, marker); status)
+        return status;
 
     auto start = std::chrono::system_clock::now();
-    auto [offers, retCursor] = context.backend->fetchBookOffers(
-        bookBase, lgrInfo.seq, limit, cursor, context.yield);
+    auto [offers, retMarker] = context.backend->fetchBookOffers(
+        bookBase, lgrInfo.seq, limit, marker, context.yield);
     auto end = std::chrono::system_clock::now();
 
     BOOST_LOG_TRIVIAL(warning)
@@ -92,10 +71,10 @@ doBookOffers(Context const& context)
                .count()
         << " milliseconds - request = " << request;
 
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-    response["ledger_index"] = lgrInfo.seq;
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+    response[JS(ledger_index)] = lgrInfo.seq;
 
-    response["offers"] = postProcessOrderBook(
+    response[JS(offers)] = postProcessOrderBook(
         offers, book, takerID, *context.backend, lgrInfo.seq, context.yield);
 
     auto end2 = std::chrono::system_clock::now();
@@ -106,8 +85,8 @@ doBookOffers(Context const& context)
                .count()
         << " milliseconds - request = " << request;
 
-    if (retCursor)
-        response["marker"] = ripple::strHex(*retCursor);
+    if (retMarker)
+        response["marker"] = ripple::strHex(*retMarker);
 
     return response;
 }

src/rpc/handlers/ChannelAuthorize.cpp

@@ -27,19 +27,13 @@ doChannelAuthorize(Context const& context)
     auto request = context.params;
     boost::json::object response = {};
 
-    if (!request.contains("channel_id"))
-        return Status{Error::rpcINVALID_PARAMS, "missingChannelID"};
-
-    if (!request.at("channel_id").is_string())
-        return Status{Error::rpcINVALID_PARAMS, "channelIDNotString"};
-
-    if (!request.contains("amount"))
+    if (!request.contains(JS(amount)))
         return Status{Error::rpcINVALID_PARAMS, "missingAmount"};
 
-    if (!request.at("amount").is_string())
+    if (!request.at(JS(amount)).is_string())
         return Status{Error::rpcINVALID_PARAMS, "amountNotString"};
 
-    if (!request.contains("key_type") && !request.contains("secret"))
+    if (!request.contains(JS(key_type)) && !request.contains(JS(secret)))
         return Status{Error::rpcINVALID_PARAMS, "missingKeyTypeOrSecret"};
 
     auto v = keypairFromRequst(request);
@@ -50,10 +44,11 @@ doChannelAuthorize(Context const& context)
         std::get<std::pair<ripple::PublicKey, ripple::SecretKey>>(v);
 
     ripple::uint256 channelId;
-    if (!channelId.parseHex(request.at("channel_id").as_string().c_str()))
-        return Status{Error::rpcCHANNEL_MALFORMED, "malformedChannelID"};
+    if (auto const status = getChannelId(request, channelId); status)
+        return status;
 
-    auto optDrops = ripple::to_uint64(request.at("amount").as_string().c_str());
+    auto optDrops =
+        ripple::to_uint64(request.at(JS(amount)).as_string().c_str());
 
     if (!optDrops)
         return Status{Error::rpcCHANNEL_AMT_MALFORMED, "couldNotParseAmount"};
@@ -67,7 +62,7 @@ doChannelAuthorize(Context const& context)
     try
     {
         auto const buf = ripple::sign(pk, sk, msg.slice());
-        response["signature"] = ripple::strHex(buf);
+        response[JS(signature)] = ripple::strHex(buf);
     }
     catch (std::exception&)
     {

src/rpc/handlers/ChannelVerify.cpp

@@ -16,33 +16,28 @@ doChannelVerify(Context const& context)
     auto request = context.params;
     boost::json::object response = {};
 
-    if (!request.contains("channel_id"))
-        return Status{Error::rpcINVALID_PARAMS, "missingChannelID"};
-
-    if (!request.at("channel_id").is_string())
-        return Status{Error::rpcINVALID_PARAMS, "channelIDNotString"};
-
-    if (!request.contains("amount"))
+    if (!request.contains(JS(amount)))
         return Status{Error::rpcINVALID_PARAMS, "missingAmount"};
 
-    if (!request.at("amount").is_string())
+    if (!request.at(JS(amount)).is_string())
         return Status{Error::rpcINVALID_PARAMS, "amountNotString"};
 
-    if (!request.contains("signature"))
+    if (!request.contains(JS(signature)))
         return Status{Error::rpcINVALID_PARAMS, "missingSignature"};
 
-    if (!request.at("signature").is_string())
+    if (!request.at(JS(signature)).is_string())
         return Status{Error::rpcINVALID_PARAMS, "signatureNotString"};
 
-    if (!request.contains("public_key"))
+    if (!request.contains(JS(public_key)))
         return Status{Error::rpcINVALID_PARAMS, "missingPublicKey"};
 
-    if (!request.at("public_key").is_string())
+    if (!request.at(JS(public_key)).is_string())
         return Status{Error::rpcINVALID_PARAMS, "publicKeyNotString"};
 
     std::optional<ripple::PublicKey> pk;
     {
-        std::string const strPk = request.at("public_key").as_string().c_str();
+        std::string const strPk =
+            request.at(JS(public_key)).as_string().c_str();
         pk = ripple::parseBase58<ripple::PublicKey>(
             ripple::TokenType::AccountPublic, strPk);
 
@@ -62,17 +57,18 @@ doChannelVerify(Context const& context)
     }
 
     ripple::uint256 channelId;
-    if (!channelId.parseHex(request.at("channel_id").as_string().c_str()))
-        return Status{Error::rpcCHANNEL_MALFORMED, "malformedChannelID"};
+    if (auto const status = getChannelId(request, channelId); status)
+        return status;
 
-    auto optDrops = ripple::to_uint64(request.at("amount").as_string().c_str());
+    auto optDrops =
+        ripple::to_uint64(request.at(JS(amount)).as_string().c_str());
 
     if (!optDrops)
         return Status{Error::rpcCHANNEL_AMT_MALFORMED, "couldNotParseAmount"};
 
     std::uint64_t drops = *optDrops;
 
-    auto sig = ripple::strUnHex(request.at("signature").as_string().c_str());
+    auto sig = ripple::strUnHex(request.at(JS(signature)).as_string().c_str());
 
     if (!sig || !sig->size())
         return Status{Error::rpcINVALID_PARAMS, "invalidSignature"};
@@ -81,7 +77,7 @@ doChannelVerify(Context const& context)
     ripple::serializePayChanAuthorization(
         msg, channelId, ripple::XRPAmount(drops));
 
-    response["signature_verified"] =
+    response[JS(signature_verified)] =
         ripple::verify(*pk, msg.slice(), ripple::makeSlice(*sig), true);
 
     return response;

src/rpc/handlers/GatewayBalances.cpp

@@ -9,17 +9,9 @@ doGatewayBalances(Context const& context)
     auto request = context.params;
     boost::json::object response = {};
 
-    if (!request.contains("account"))
-        return Status{Error::rpcINVALID_PARAMS, "missingAccount"};
-
-    if (!request.at("account").is_string())
-        return Status{Error::rpcINVALID_PARAMS, "accountNotString"};
-
-    auto accountID =
-        accountFromStringStrict(request.at("account").as_string().c_str());
-
-    if (!accountID)
-        return Status{Error::rpcINVALID_PARAMS, "malformedAccount"};
+    ripple::AccountID accountID;
+    if (auto const status = getAccount(request, accountID); status)
+        return status;
 
     auto v = ledgerInfoFromRequest(context);
     if (auto status = std::get_if<Status>(&v))
@@ -81,7 +73,7 @@ doGatewayBalances(Context const& context)
 
         if (!valid)
         {
-            response["error"] = "invalidHotWallet";
+            response[JS(error)] = "invalidHotWallet";
             return response;
         }
     }
@@ -148,7 +140,7 @@ doGatewayBalances(Context const& context)
 
     traverseOwnedNodes(
         *context.backend,
-        *accountID,
+        accountID,
         lgrInfo.seq,
         std::numeric_limits<std::uint32_t>::max(),
         {},
@@ -162,7 +154,7 @@ doGatewayBalances(Context const& context)
         {
             obj[ripple::to_string(k)] = v.getText();
         }
-        response["obligations"] = std::move(obj);
+        response[JS(obligations)] = std::move(obj);
     }
 
     auto toJson =
@@ -177,9 +169,9 @@ doGatewayBalances(Context const& context)
                     for (auto const& balance : accBalances)
                     {
                         boost::json::object entry;
-                        entry["currency"] =
+                        entry[JS(currency)] =
                             ripple::to_string(balance.issue().currency);
-                        entry["value"] = balance.getText();
+                        entry[JS(value)] = balance.getText();
                         arr.push_back(std::move(entry));
                     }
                     obj[ripple::to_string(accId)] = std::move(arr);
@@ -189,14 +181,14 @@ doGatewayBalances(Context const& context)
         };
 
     if (auto balances = toJson(hotBalances); balances.size())
-        response["balances"] = balances;
+        response[JS(balances)] = balances;
     if (auto balances = toJson(frozenBalances); balances.size())
-        response["frozen_balances"] = balances;
+        response[JS(frozen_balances)] = balances;
     if (auto balances = toJson(assets); assets.size())
-        response["assets"] = toJson(assets);
-    response["account"] = request.at("account");
-    response["ledger_index"] = lgrInfo.seq;
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
+        response[JS(assets)] = toJson(assets);
+    response[JS(account)] = request.at(JS(account));
+    response[JS(ledger_index)] = lgrInfo.seq;
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
     return response;
 }
 }  // namespace RPC

src/rpc/handlers/Ledger.cpp

@@ -10,30 +10,30 @@ doLedger(Context const& context)
     boost::json::object response = {};
 
     bool binary = false;
-    if (params.contains("binary"))
+    if (params.contains(JS(binary)))
     {
-        if (!params.at("binary").is_bool())
+        if (!params.at(JS(binary)).is_bool())
             return Status{Error::rpcINVALID_PARAMS, "binaryFlagNotBool"};
 
-        binary = params.at("binary").as_bool();
+        binary = params.at(JS(binary)).as_bool();
     }
 
     bool transactions = false;
-    if (params.contains("transactions"))
+    if (params.contains(JS(transactions)))
     {
-        if (!params.at("transactions").is_bool())
+        if (!params.at(JS(transactions)).is_bool())
             return Status{Error::rpcINVALID_PARAMS, "transactionsFlagNotBool"};
 
-        transactions = params.at("transactions").as_bool();
+        transactions = params.at(JS(transactions)).as_bool();
     }
 
     bool expand = false;
-    if (params.contains("expand"))
+    if (params.contains(JS(expand)))
     {
-        if (!params.at("expand").is_bool())
+        if (!params.at(JS(expand)).is_bool())
             return Status{Error::rpcINVALID_PARAMS, "expandFlagNotBool"};
 
-        expand = params.at("expand").as_bool();
+        expand = params.at(JS(expand)).as_bool();
     }
 
     bool diff = false;
@@ -54,35 +54,34 @@ doLedger(Context const& context)
     boost::json::object header;
     if (binary)
     {
-        header["ledger_data"] = ripple::strHex(ledgerInfoToBlob(lgrInfo));
+        header[JS(ledger_data)] = ripple::strHex(ledgerInfoToBlob(lgrInfo));
     }
     else
     {
-        header["accepted"] = true;
-        header["account_hash"] = ripple::strHex(lgrInfo.accountHash);
-        header["close_flags"] = lgrInfo.closeFlags;
-        header["close_time"] = lgrInfo.closeTime.time_since_epoch().count();
-        header["close_time_human"] = ripple::to_string(lgrInfo.closeTime);
-        ;
-        header["close_time_resolution"] = lgrInfo.closeTimeResolution.count();
-        header["closed"] = true;
-        header["hash"] = ripple::strHex(lgrInfo.hash);
-        header["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-        header["ledger_index"] = std::to_string(lgrInfo.seq);
-        header["parent_close_time"] =
+        header[JS(accepted)] = true;
+        header[JS(account_hash)] = ripple::strHex(lgrInfo.accountHash);
+        header[JS(close_flags)] = lgrInfo.closeFlags;
+        header[JS(close_time)] = lgrInfo.closeTime.time_since_epoch().count();
+        header[JS(close_time_human)] = ripple::to_string(lgrInfo.closeTime);
+        header[JS(close_time_resolution)] = lgrInfo.closeTimeResolution.count();
+        header[JS(closed)] = true;
+        header[JS(hash)] = ripple::strHex(lgrInfo.hash);
+        header[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+        header[JS(ledger_index)] = std::to_string(lgrInfo.seq);
+        header[JS(parent_close_time)] =
             lgrInfo.parentCloseTime.time_since_epoch().count();
-        header["parent_hash"] = ripple::strHex(lgrInfo.parentHash);
-        header["seqNum"] = std::to_string(lgrInfo.seq);
-        header["totalCoins"] = ripple::to_string(lgrInfo.drops);
-        header["total_coins"] = ripple::to_string(lgrInfo.drops);
-        header["transaction_hash"] = ripple::strHex(lgrInfo.txHash);
+        header[JS(parent_hash)] = ripple::strHex(lgrInfo.parentHash);
+        header[JS(seqNum)] = std::to_string(lgrInfo.seq);
+        header[JS(totalCoins)] = ripple::to_string(lgrInfo.drops);
+        header[JS(total_coins)] = ripple::to_string(lgrInfo.drops);
+        header[JS(transaction_hash)] = ripple::strHex(lgrInfo.txHash);
     }
-    header["closed"] = true;
+    header[JS(closed)] = true;
 
     if (transactions)
     {
-        header["transactions"] = boost::json::value(boost::json::array_kind);
-        boost::json::array& jsonTxs = header.at("transactions").as_array();
+        header[JS(transactions)] = boost::json::value(boost::json::array_kind);
+        boost::json::array& jsonTxs = header.at(JS(transactions)).as_array();
         if (expand)
         {
             auto txns = context.backend->fetchAllTransactionsInLedger(
@@ -98,14 +97,14 @@ doLedger(Context const& context)
                     {
                         auto [txn, meta] = toExpandedJson(obj);
                         entry = txn;
-                        entry["metaData"] = meta;
+                        entry[JS(metaData)] = meta;
                     }
                     else
                     {
-                        entry["tx_blob"] = ripple::strHex(obj.transaction);
-                        entry["meta"] = ripple::strHex(obj.metadata);
+                        entry[JS(tx_blob)] = ripple::strHex(obj.transaction);
+                        entry[JS(meta)] = ripple::strHex(obj.metadata);
                     }
-                    // entry["ledger_index"] = obj.ledgerSequence;
+                    // entry[JS(ledger_index)] = obj.ledgerSequence;
                     return entry;
                 });
         }
@@ -133,7 +132,7 @@ doLedger(Context const& context)
         for (auto const& obj : diff)
         {
             boost::json::object entry;
-            entry["id"] = ripple::strHex(obj.key);
+            entry["object_id"] = ripple::strHex(obj.key);
             if (binary)
                 entry["object"] = ripple::strHex(obj.blob);
             else if (obj.blob.size())
@@ -149,9 +148,9 @@ doLedger(Context const& context)
         }
     }
 
-    response["ledger"] = header;
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-    response["ledger_index"] = lgrInfo.seq;
+    response[JS(ledger)] = header;
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+    response[JS(ledger_index)] = lgrInfo.seq;
     return response;
 }
 

src/rpc/handlers/LedgerData.cpp

@@ -28,23 +28,15 @@ doLedgerData(Context const& context)
     auto request = context.params;
     boost::json::object response = {};
 
-    bool binary = false;
-    if (request.contains("binary"))
-    {
-        if (!request.at("binary").is_bool())
-            return Status{Error::rpcINVALID_PARAMS, "binaryFlagNotBool"};
+    bool const binary = getBool(request, "binary", false);
 
-        binary = request.at("binary").as_bool();
-    }
+    std::uint32_t limit;
+    if (auto const status = getLimit(context, limit); status)
+        return status;
 
-    std::size_t limit = binary ? 2048 : 256;
-    if (request.contains("limit"))
-    {
-        if (!request.at("limit").is_int64())
-            return Status{Error::rpcINVALID_PARAMS, "limitNotInteger"};
+    if (!binary)
+        limit = std::clamp(limit, {1}, {256});
 
-        limit = boost::json::value_to<int>(request.at("limit"));
-    }
     bool outOfOrder = false;
     if (request.contains("out_of_order"))
     {
@@ -53,18 +45,18 @@ doLedgerData(Context const& context)
         outOfOrder = request.at("out_of_order").as_bool();
     }
 
-    std::optional<ripple::uint256> cursor;
-    std::optional<uint32_t> diffCursor;
-    if (request.contains("marker"))
+    std::optional<ripple::uint256> marker;
+    std::optional<uint32_t> diffMarker;
+    if (request.contains(JS(marker)))
     {
-        if (!request.at("marker").is_string())
+        if (!request.at(JS(marker)).is_string())
         {
             if (outOfOrder)
             {
-                if (!request.at("marker").is_int64())
+                if (!request.at(JS(marker)).is_int64())
                     return Status{
                         Error::rpcINVALID_PARAMS, "markerNotStringOrInt"};
-                diffCursor = value_to<uint32_t>(request.at("marker"));
+                diffMarker = value_to<uint32_t>(request.at(JS(marker)));
             }
             else
                 return Status{Error::rpcINVALID_PARAMS, "markerNotString"};
@@ -73,8 +65,8 @@ doLedgerData(Context const& context)
         {
             BOOST_LOG_TRIVIAL(debug) << __func__ << " : parsing marker";
 
-            cursor = ripple::uint256{};
-            if (!cursor->parseHex(request.at("marker").as_string().c_str()))
+            marker = ripple::uint256{};
+            if (!marker->parseHex(request.at(JS(marker)).as_string().c_str()))
                 return Status{Error::rpcINVALID_PARAMS, "markerMalformed"};
         }
     }
@@ -84,49 +76,58 @@ doLedgerData(Context const& context)
         return *status;
 
     auto lgrInfo = std::get<ripple::LedgerInfo>(v);
+
     boost::json::object header;
-    // no cursor means this is the first call, so we return header info
-    if (!cursor)
+    // no marker means this is the first call, so we return header info
+    if (!request.contains(JS(marker)))
     {
         if (binary)
         {
-            header["ledger_data"] = ripple::strHex(ledgerInfoToBlob(lgrInfo));
+            header[JS(ledger_data)] = ripple::strHex(ledgerInfoToBlob(lgrInfo));
         }
         else
         {
-            header["accepted"] = true;
-            header["account_hash"] = ripple::strHex(lgrInfo.accountHash);
-            header["close_flags"] = lgrInfo.closeFlags;
-            header["close_time"] = lgrInfo.closeTime.time_since_epoch().count();
-            header["close_time_human"] = ripple::to_string(lgrInfo.closeTime);
-            ;
-            header["close_time_resolution"] =
+            header[JS(accepted)] = true;
+            header[JS(account_hash)] = ripple::strHex(lgrInfo.accountHash);
+            header[JS(close_flags)] = lgrInfo.closeFlags;
+            header[JS(close_time)] =
+                lgrInfo.closeTime.time_since_epoch().count();
+            header[JS(close_time_human)] = ripple::to_string(lgrInfo.closeTime);
+            header[JS(close_time_resolution)] =
                 lgrInfo.closeTimeResolution.count();
-            header["closed"] = true;
-            header["hash"] = ripple::strHex(lgrInfo.hash);
-            header["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-            header["ledger_index"] = std::to_string(lgrInfo.seq);
-            header["parent_close_time"] =
+            header[JS(closed)] = true;
+            header[JS(hash)] = ripple::strHex(lgrInfo.hash);
+            header[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+            header[JS(ledger_index)] = std::to_string(lgrInfo.seq);
+            header[JS(parent_close_time)] =
                 lgrInfo.parentCloseTime.time_since_epoch().count();
-            header["parent_hash"] = ripple::strHex(lgrInfo.parentHash);
-            header["seqNum"] = std::to_string(lgrInfo.seq);
-            header["totalCoins"] = ripple::to_string(lgrInfo.drops);
-            header["total_coins"] = ripple::to_string(lgrInfo.drops);
-            header["transaction_hash"] = ripple::strHex(lgrInfo.txHash);
-
-            response["ledger"] = header;
+            header[JS(parent_hash)] = ripple::strHex(lgrInfo.parentHash);
+            header[JS(seqNum)] = std::to_string(lgrInfo.seq);
+            header[JS(totalCoins)] = ripple::to_string(lgrInfo.drops);
+            header[JS(total_coins)] = ripple::to_string(lgrInfo.drops);
+            header[JS(transaction_hash)] = ripple::strHex(lgrInfo.txHash);
         }
+
+        response[JS(ledger)] = header;
     }
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-    response["ledger_index"] = lgrInfo.seq;
+    else
+    {
+        if (!outOfOrder &&
+            !context.backend->fetchLedgerObject(
+                *marker, lgrInfo.seq, context.yield))
+            return Status{Error::rpcINVALID_PARAMS, "markerDoesNotExist"};
+    }
+
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+    response[JS(ledger_index)] = lgrInfo.seq;
 
     auto start = std::chrono::system_clock::now();
     std::vector<Backend::LedgerObject> results;
-    if (diffCursor)
+    if (diffMarker)
     {
         assert(outOfOrder);
         auto diff =
-            context.backend->fetchLedgerDiff(*diffCursor, context.yield);
+            context.backend->fetchLedgerDiff(*diffMarker, context.yield);
         std::vector<ripple::uint256> keys;
         for (auto&& [key, object] : diff)
         {
@@ -143,13 +144,13 @@ doLedgerData(Context const& context)
             if (obj.size())
                 results.push_back({std::move(keys[i]), std::move(obj)});
         }
-        if (*diffCursor > lgrInfo.seq)
-            response["marker"] = *diffCursor - 1;
+        if (*diffMarker > lgrInfo.seq)
+            response["marker"] = *diffMarker - 1;
     }
     else
     {
         auto page = context.backend->fetchLedgerPage(
-            cursor, lgrInfo.seq, limit, outOfOrder, context.yield);
+            marker, lgrInfo.seq, limit, outOfOrder, context.yield);
         results = std::move(page.objects);
         if (page.cursor)
             response["marker"] = ripple::strHex(*(page.cursor));
@@ -175,14 +176,14 @@ doLedgerData(Context const& context)
         if (binary)
         {
             boost::json::object entry;
-            entry["data"] = ripple::serializeHex(sle);
-            entry["index"] = ripple::to_string(sle.key());
+            entry[JS(data)] = ripple::serializeHex(sle);
+            entry[JS(index)] = ripple::to_string(sle.key());
             objects.push_back(std::move(entry));
         }
         else
             objects.push_back(toJson(sle));
     }
-    response["state"] = std::move(objects);
+    response[JS(state)] = std::move(objects);
     auto end2 = std::chrono::system_clock::now();
 
     time = std::chrono::duration_cast<std::chrono::microseconds>(end2 - end)

src/rpc/handlers/LedgerEntry.cpp

@@ -20,8 +20,7 @@ doLedgerEntry(Context const& context)
     auto request = context.params;
     boost::json::object response = {};
 
-    bool binary =
-        request.contains("binary") ? request.at("binary").as_bool() : false;
+    bool const binary = getBool(request, "binary", false);
 
     auto v = ledgerInfoFromRequest(context);
     if (auto status = std::get_if<Status>(&v))
@@ -30,59 +29,64 @@ doLedgerEntry(Context const& context)
     auto lgrInfo = std::get<ripple::LedgerInfo>(v);
 
     ripple::uint256 key;
-    if (request.contains("index"))
+    if (request.contains(JS(index)))
     {
-        if (!request.at("index").is_string())
+        if (!request.at(JS(index)).is_string())
             return Status{Error::rpcINVALID_PARAMS, "indexNotString"};
 
-        if (!key.parseHex(request.at("index").as_string().c_str()))
+        if (!key.parseHex(request.at(JS(index)).as_string().c_str()))
             return Status{Error::rpcINVALID_PARAMS, "malformedIndex"};
     }
-    else if (request.contains("account_root"))
+    else if (request.contains(JS(account_root)))
     {
-        if (!request.at("account_root").is_string())
+        if (!request.at(JS(account_root)).is_string())
             return Status{Error::rpcINVALID_PARAMS, "account_rootNotString"};
 
         auto const account = ripple::parseBase58<ripple::AccountID>(
-            request.at("account_root").as_string().c_str());
+            request.at(JS(account_root)).as_string().c_str());
         if (!account || account->isZero())
             return Status{Error::rpcINVALID_PARAMS, "malformedAddress"};
         else
             key = ripple::keylet::account(*account).key;
     }
-    else if (request.contains("check"))
+    else if (request.contains(JS(check)))
     {
-        if (!request.at("check").is_string())
+        if (!request.at(JS(check)).is_string())
             return Status{Error::rpcINVALID_PARAMS, "checkNotString"};
 
-        if (!key.parseHex(request.at("check").as_string().c_str()))
+        if (!key.parseHex(request.at(JS(check)).as_string().c_str()))
         {
             return Status{Error::rpcINVALID_PARAMS, "checkMalformed"};
         }
     }
-    else if (request.contains("deposit_preauth"))
+    else if (request.contains(JS(deposit_preauth)))
     {
-        if (!request.at("deposit_preauth").is_object())
+        if (!request.at(JS(deposit_preauth)).is_object())
         {
-            if (!request.at("deposit_preauth").is_string() ||
+            if (!request.at(JS(deposit_preauth)).is_string() ||
                 !key.parseHex(
-                    request.at("deposit_preauth").as_string().c_str()))
+                    request.at(JS(deposit_preauth)).as_string().c_str()))
             {
                 return Status{
                     Error::rpcINVALID_PARAMS, "deposit_preauthMalformed"};
             }
         }
         else if (
-            !request.at("deposit_preauth").as_object().contains("owner") ||
-            !request.at("deposit_preauth").as_object().at("owner").is_string())
+            !request.at(JS(deposit_preauth)).as_object().contains(JS(owner)) ||
+            !request.at(JS(deposit_preauth))
+                 .as_object()
+                 .at(JS(owner))
+                 .is_string())
         {
             return Status{Error::rpcINVALID_PARAMS, "ownerNotString"};
         }
         else if (
-            !request.at("deposit_preauth").as_object().contains("authorized") ||
-            !request.at("deposit_preauth")
+            !request.at(JS(deposit_preauth))
                  .as_object()
-                 .at("authorized")
+                 .contains(JS(authorized)) ||
+            !request.at(JS(deposit_preauth))
+                 .as_object()
+                 .at(JS(authorized))
                  .is_string())
         {
             return Status{Error::rpcINVALID_PARAMS, "authorizedNotString"};
@@ -90,13 +94,13 @@ doLedgerEntry(Context const& context)
         else
         {
             boost::json::object const& deposit_preauth =
-                request.at("deposit_preauth").as_object();
+                request.at(JS(deposit_preauth)).as_object();
 
             auto const owner = ripple::parseBase58<ripple::AccountID>(
-                deposit_preauth.at("owner").as_string().c_str());
+                deposit_preauth.at(JS(owner)).as_string().c_str());
 
             auto const authorized = ripple::parseBase58<ripple::AccountID>(
-                deposit_preauth.at("authorized").as_string().c_str());
+                deposit_preauth.at(JS(authorized)).as_string().c_str());
 
             if (!owner)
                 return Status{Error::rpcINVALID_PARAMS, "malformedOwner"};
@@ -106,37 +110,37 @@ doLedgerEntry(Context const& context)
                 key = ripple::keylet::depositPreauth(*owner, *authorized).key;
         }
     }
-    else if (request.contains("directory"))
+    else if (request.contains(JS(directory)))
     {
-        if (!request.at("directory").is_object())
+        if (!request.at(JS(directory)).is_object())
         {
-            if (!request.at("directory").is_string())
+            if (!request.at(JS(directory)).is_string())
                 return Status{Error::rpcINVALID_PARAMS, "directoryNotString"};
 
-            if (!key.parseHex(request.at("directory").as_string().c_str()))
+            if (!key.parseHex(request.at(JS(directory)).as_string().c_str()))
             {
                 return Status{Error::rpcINVALID_PARAMS, "malformedDirectory"};
             }
         }
         else if (
-            request.at("directory").as_object().contains("sub_index") &&
-            !request.at("directory").as_object().at("sub_index").is_int64())
+            request.at(JS(directory)).as_object().contains(JS(sub_index)) &&
+            !request.at(JS(directory)).as_object().at(JS(sub_index)).is_int64())
         {
             return Status{Error::rpcINVALID_PARAMS, "sub_indexNotInt"};
         }
         else
         {
-            auto directory = request.at("directory").as_object();
-            std::uint64_t subIndex = directory.contains("sub_index")
+            auto directory = request.at(JS(directory)).as_object();
+            std::uint64_t subIndex = directory.contains(JS(sub_index))
                 ? boost::json::value_to<std::uint64_t>(
-                      directory.at("sub_index"))
+                      directory.at(JS(sub_index)))
                 : 0;
 
-            if (directory.contains("dir_root"))
+            if (directory.contains(JS(dir_root)))
             {
                 ripple::uint256 uDirRoot;
 
-                if (directory.contains("owner"))
+                if (directory.contains(JS(owner)))
                 {
                     // May not specify both dir_root and owner.
                     return Status{
@@ -144,7 +148,7 @@ doLedgerEntry(Context const& context)
                         "mayNotSpecifyBothDirRootAndOwner"};
                 }
                 else if (!uDirRoot.parseHex(
-                             directory.at("dir_root").as_string().c_str()))
+                             directory.at(JS(dir_root)).as_string().c_str()))
                 {
                     return Status{Error::rpcINVALID_PARAMS, "malformedDirRoot"};
                 }
@@ -153,10 +157,10 @@ doLedgerEntry(Context const& context)
                     key = ripple::keylet::page(uDirRoot, subIndex).key;
                 }
             }
-            else if (directory.contains("owner"))
+            else if (directory.contains(JS(owner)))
             {
                 auto const ownerID = ripple::parseBase58<ripple::AccountID>(
-                    directory.at("owner").as_string().c_str());
+                    directory.at(JS(owner)).as_string().c_str());
 
                 if (!ownerID)
                 {
@@ -176,31 +180,31 @@ doLedgerEntry(Context const& context)
             }
         }
     }
-    else if (request.contains("escrow"))
+    else if (request.contains(JS(escrow)))
     {
-        if (!request.at("escrow").is_object())
+        if (!request.at(JS(escrow)).is_object())
         {
-            if (!key.parseHex(request.at("escrow").as_string().c_str()))
+            if (!key.parseHex(request.at(JS(escrow)).as_string().c_str()))
                 return Status{Error::rpcINVALID_PARAMS, "malformedEscrow"};
         }
         else if (
-            !request.at("escrow").as_object().contains("owner") ||
-            !request.at("escrow").as_object().at("owner").is_string())
+            !request.at(JS(escrow)).as_object().contains(JS(owner)) ||
+            !request.at(JS(escrow)).as_object().at(JS(owner)).is_string())
         {
             return Status{Error::rpcINVALID_PARAMS, "malformedOwner"};
         }
         else if (
-            !request.at("escrow").as_object().contains("seq") ||
-            !request.at("escrow").as_object().at("seq").is_int64())
+            !request.at(JS(escrow)).as_object().contains(JS(seq)) ||
+            !request.at(JS(escrow)).as_object().at(JS(seq)).is_int64())
         {
             return Status{Error::rpcINVALID_PARAMS, "malformedSeq"};
         }
         else
         {
             auto const id =
-                ripple::parseBase58<ripple::AccountID>(request.at("escrow")
+                ripple::parseBase58<ripple::AccountID>(request.at(JS(escrow))
                                                            .as_object()
-                                                           .at("owner")
+                                                           .at(JS(owner))
                                                            .as_string()
                                                            .c_str());
 
@@ -209,120 +213,122 @@ doLedgerEntry(Context const& context)
             else
             {
                 std::uint32_t seq =
-                    request.at("escrow").as_object().at("seq").as_int64();
+                    request.at(JS(escrow)).as_object().at(JS(seq)).as_int64();
                 key = ripple::keylet::escrow(*id, seq).key;
             }
         }
     }
-    else if (request.contains("offer"))
+    else if (request.contains(JS(offer)))
     {
-        if (!request.at("offer").is_object())
+        if (!request.at(JS(offer)).is_object())
         {
-            if (!key.parseHex(request.at("offer").as_string().c_str()))
+            if (!key.parseHex(request.at(JS(offer)).as_string().c_str()))
                 return Status{Error::rpcINVALID_PARAMS, "malformedOffer"};
         }
         else if (
-            !request.at("offer").as_object().contains("account") ||
-            !request.at("offer").as_object().at("account").is_string())
+            !request.at(JS(offer)).as_object().contains(JS(account)) ||
+            !request.at(JS(offer)).as_object().at(JS(account)).is_string())
         {
             return Status{Error::rpcINVALID_PARAMS, "malformedAccount"};
         }
         else if (
-            !request.at("offer").as_object().contains("seq") ||
-            !request.at("offer").as_object().at("seq").is_int64())
+            !request.at(JS(offer)).as_object().contains(JS(seq)) ||
+            !request.at(JS(offer)).as_object().at(JS(seq)).is_int64())
         {
             return Status{Error::rpcINVALID_PARAMS, "malformedSeq"};
         }
         else
         {
-            auto offer = request.at("offer").as_object();
+            auto offer = request.at(JS(offer)).as_object();
             auto const id = ripple::parseBase58<ripple::AccountID>(
-                offer.at("account").as_string().c_str());
+                offer.at(JS(account)).as_string().c_str());
 
             if (!id)
                 return Status{Error::rpcINVALID_PARAMS, "malformedAccount"};
             else
             {
                 std::uint32_t seq =
-                    boost::json::value_to<std::uint32_t>(offer.at("seq"));
+                    boost::json::value_to<std::uint32_t>(offer.at(JS(seq)));
                 key = ripple::keylet::offer(*id, seq).key;
             }
         }
     }
-    else if (request.contains("payment_channel"))
+    else if (request.contains(JS(payment_channel)))
     {
-        if (!request.at("payment_channel").is_string())
+        if (!request.at(JS(payment_channel)).is_string())
             return Status{Error::rpcINVALID_PARAMS, "paymentChannelNotString"};
 
-        if (!key.parseHex(request.at("payment_channel").as_string().c_str()))
+        if (!key.parseHex(request.at(JS(payment_channel)).as_string().c_str()))
             return Status{Error::rpcINVALID_PARAMS, "malformedPaymentChannel"};
     }
-    else if (request.contains("ripple_state"))
+    else if (request.contains(JS(ripple_state)))
     {
-        if (!request.at("ripple_state").is_object())
+        if (!request.at(JS(ripple_state)).is_object())
             return Status{Error::rpcINVALID_PARAMS, "rippleStateNotObject"};
 
         ripple::Currency currency;
         boost::json::object const& state =
-            request.at("ripple_state").as_object();
+            request.at(JS(ripple_state)).as_object();
 
-        if (!state.contains("currency") || !state.at("currency").is_string())
+        if (!state.contains(JS(currency)) ||
+            !state.at(JS(currency)).is_string())
         {
             return Status{Error::rpcINVALID_PARAMS, "malformedCurrency"};
         }
 
-        if (!state.contains("accounts") || !state.at("accounts").is_array() ||
-            2 != state.at("accounts").as_array().size() ||
-            !state.at("accounts").as_array().at(0).is_string() ||
-            !state.at("accounts").as_array().at(1).is_string() ||
-            (state.at("accounts").as_array().at(0).as_string() ==
-             state.at("accounts").as_array().at(1).as_string()))
+        if (!state.contains(JS(accounts)) ||
+            !state.at(JS(accounts)).is_array() ||
+            2 != state.at(JS(accounts)).as_array().size() ||
+            !state.at(JS(accounts)).as_array().at(0).is_string() ||
+            !state.at(JS(accounts)).as_array().at(1).is_string() ||
+            (state.at(JS(accounts)).as_array().at(0).as_string() ==
+             state.at(JS(accounts)).as_array().at(1).as_string()))
         {
             return Status{Error::rpcINVALID_PARAMS, "malformedAccounts"};
         }
 
         auto const id1 = ripple::parseBase58<ripple::AccountID>(
-            state.at("accounts").as_array().at(0).as_string().c_str());
+            state.at(JS(accounts)).as_array().at(0).as_string().c_str());
         auto const id2 = ripple::parseBase58<ripple::AccountID>(
-            state.at("accounts").as_array().at(1).as_string().c_str());
+            state.at(JS(accounts)).as_array().at(1).as_string().c_str());
 
         if (!id1 || !id2)
             return Status{Error::rpcINVALID_PARAMS, "malformedAccounts"};
 
         else if (!ripple::to_currency(
-                     currency, state.at("currency").as_string().c_str()))
+                     currency, state.at(JS(currency)).as_string().c_str()))
             return Status{Error::rpcINVALID_PARAMS, "malformedCurrency"};
 
         key = ripple::keylet::line(*id1, *id2, currency).key;
     }
-    else if (request.contains("ticket"))
+    else if (request.contains(JS(ticket)))
     {
-        if (!request.at("ticket").is_object())
+        if (!request.at(JS(ticket)).is_object())
         {
-            if (!request.at("ticket").is_string())
+            if (!request.at(JS(ticket)).is_string())
                 return Status{Error::rpcINVALID_PARAMS, "ticketNotString"};
 
-            if (!key.parseHex(request.at("ticket").as_string().c_str()))
+            if (!key.parseHex(request.at(JS(ticket)).as_string().c_str()))
                 return Status{Error::rpcINVALID_PARAMS, "malformedTicket"};
         }
         else if (
-            !request.at("ticket").as_object().contains("account") ||
-            !request.at("ticket").as_object().at("account").is_string())
+            !request.at(JS(ticket)).as_object().contains(JS(account)) ||
+            !request.at(JS(ticket)).as_object().at(JS(account)).is_string())
         {
             return Status{Error::rpcINVALID_PARAMS, "malformedTicketAccount"};
         }
         else if (
-            !request.at("ticket").as_object().contains("ticket_seq") ||
-            !request.at("ticket").as_object().at("ticket_seq").is_int64())
+            !request.at(JS(ticket)).as_object().contains(JS(ticket_seq)) ||
+            !request.at(JS(ticket)).as_object().at(JS(ticket_seq)).is_int64())
         {
             return Status{Error::rpcINVALID_PARAMS, "malformedTicketSeq"};
         }
         else
         {
             auto const id =
-                ripple::parseBase58<ripple::AccountID>(request.at("ticket")
+                ripple::parseBase58<ripple::AccountID>(request.at(JS(ticket))
                                                            .as_object()
-                                                           .at("account")
+                                                           .at(JS(account))
                                                            .as_string()
                                                            .c_str());
 
@@ -331,8 +337,10 @@ doLedgerEntry(Context const& context)
                     Error::rpcINVALID_PARAMS, "malformedTicketAccount"};
             else
             {
-                std::uint32_t seq =
-                    request.at("offer").as_object().at("ticket_seq").as_int64();
+                std::uint32_t seq = request.at(JS(offer))
+                                        .as_object()
+                                        .at(JS(ticket_seq))
+                                        .as_int64();
 
                 key = ripple::getTicketIndex(*id, seq);
             }
@@ -343,27 +351,25 @@ doLedgerEntry(Context const& context)
         return Status{Error::rpcINVALID_PARAMS, "unknownOption"};
     }
 
-    auto start = std::chrono::system_clock::now();
     auto dbResponse =
         context.backend->fetchLedgerObject(key, lgrInfo.seq, context.yield);
-    auto end = std::chrono::system_clock::now();
 
     if (!dbResponse or dbResponse->size() == 0)
-        return Status{Error::rpcOBJECT_NOT_FOUND, "entryNotFound"};
+        return Status{"entryNotFound"};
 
-    response["index"] = ripple::strHex(key);
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
-    response["ledger_index"] = lgrInfo.seq;
+    response[JS(index)] = ripple::strHex(key);
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
+    response[JS(ledger_index)] = lgrInfo.seq;
 
     if (binary)
     {
-        response["node_binary"] = ripple::strHex(*dbResponse);
+        response[JS(node_binary)] = ripple::strHex(*dbResponse);
     }
     else
     {
         ripple::STLedgerEntry sle{
             ripple::SerialIter{dbResponse->data(), dbResponse->size()}, key};
-        response["node"] = toJson(sle);
+        response[JS(node)] = toJson(sle);
     }
 
     return response;

src/rpc/handlers/LedgerRange.cpp

@@ -16,11 +16,11 @@ doLedgerRange(Context const& context)
     }
     else
     {
-        response["ledger_index_min"] = range->minSequence;
-        response["ledger_index_max"] = range->maxSequence;
+        response[JS(ledger_index_min)] = range->minSequence;
+        response[JS(ledger_index_max)] = range->maxSequence;
     }
 
     return response;
 }
 
-}  // namespace RPC
+}  // namespace RPC

src/rpc/handlers/NFTInfo.cpp

@@ -0,0 +1,146 @@
+#include <ripple/app/tx/impl/details/NFTokenUtils.h>
+#include <ripple/protocol/Indexes.h>
+#include <boost/json.hpp>
+
+#include <backend/BackendInterface.h>
+#include <rpc/RPCHelpers.h>
+
+// {
+//   nft_id: <ident>
+//   ledger_hash: <ledger>
+//   ledger_index: <ledger_index>
+// }
+
+namespace RPC {
+
+std::variant<std::monostate, std::string, Status>
+getURI(Backend::NFT const& dbResponse, Context const& context)
+{
+    // Fetch URI from ledger
+    // The correct page will be > bookmark and <= last. We need to calculate
+    // the first possible page however, since bookmark is not guaranteed to
+    // exist.
+    auto const bookmark = ripple::keylet::nftpage(
+        ripple::keylet::nftpage_min(dbResponse.owner), dbResponse.tokenID);
+    auto const last = ripple::keylet::nftpage_max(dbResponse.owner);
+
+    ripple::uint256 nextKey = last.key;
+    std::optional<ripple::STLedgerEntry> sle;
+
+    // when this loop terminates, `sle` will contain the correct page for
+    // this NFT.
+    //
+    // 1) We start at the last NFTokenPage, which is guaranteed to exist,
+    // grab the object from the DB and deserialize it.
+    //
+    // 2) If that NFTokenPage has a PreviousPageMin value and the
+    // PreviousPageMin value is > bookmark, restart loop. Otherwise
+    // terminate and use the `sle` from this iteration.
+    do
+    {
+        auto const blob = context.backend->fetchLedgerObject(
+            ripple::Keylet(ripple::ltNFTOKEN_PAGE, nextKey).key,
+            dbResponse.ledgerSequence,
+            context.yield);
+
+        if (!blob || blob->size() == 0)
+            return Status{
+                Error::rpcINTERNAL, "Cannot find NFTokenPage for this NFT"};
+
+        sle = ripple::STLedgerEntry(
+            ripple::SerialIter{blob->data(), blob->size()}, nextKey);
+
+        if (sle->isFieldPresent(ripple::sfPreviousPageMin))
+            nextKey = sle->getFieldH256(ripple::sfPreviousPageMin);
+
+    } while (sle && sle->key() != nextKey && nextKey > bookmark.key);
+
+    if (!sle)
+        return Status{
+            Error::rpcINTERNAL, "Cannot find NFTokenPage for this NFT"};
+
+    auto const nfts = sle->getFieldArray(ripple::sfNFTokens);
+    auto const nft = std::find_if(
+        nfts.begin(),
+        nfts.end(),
+        [&dbResponse](ripple::STObject const& candidate) {
+            return candidate.getFieldH256(ripple::sfNFTokenID) ==
+                dbResponse.tokenID;
+        });
+
+    if (nft == nfts.end())
+        return Status{
+            Error::rpcINTERNAL, "Cannot find NFTokenPage for this NFT"};
+
+    ripple::Blob const uriField = nft->getFieldVL(ripple::sfURI);
+
+    // NOTE this cannot use a ternary or value_or because then the
+    // expression's type is unclear. We want to explicitly set the `uri`
+    // field to null when not present to avoid any confusion.
+    if (std::string const uri = std::string(uriField.begin(), uriField.end());
+        uri.size() > 0)
+        return uri;
+    return std::monostate{};
+}
+
+Result
+doNFTInfo(Context const& context)
+{
+    auto request = context.params;
+    boost::json::object response = {};
+
+    if (!request.contains("nft_id"))
+        return Status{Error::rpcINVALID_PARAMS, "Missing nft_id"};
+
+    auto const& jsonTokenID = request.at("nft_id");
+    if (!jsonTokenID.is_string())
+        return Status{Error::rpcINVALID_PARAMS, "nft_id is not a string"};
+
+    ripple::uint256 tokenID;
+    if (!tokenID.parseHex(jsonTokenID.as_string().c_str()))
+        return Status{Error::rpcINVALID_PARAMS, "Malformed nft_id"};
+
+    // We only need to fetch the ledger header because the ledger hash is
+    // supposed to be included in the response. The ledger sequence is specified
+    // in the request
+    auto v = ledgerInfoFromRequest(context);
+    if (auto status = std::get_if<Status>(&v))
+        return *status;
+    ripple::LedgerInfo lgrInfo = std::get<ripple::LedgerInfo>(v);
+
+    std::optional<Backend::NFT> dbResponse =
+        context.backend->fetchNFT(tokenID, lgrInfo.seq, context.yield);
+    if (!dbResponse)
+        return Status{Error::rpcOBJECT_NOT_FOUND, "NFT not found"};
+
+    response["nft_id"] = ripple::strHex(dbResponse->tokenID);
+    response["ledger_index"] = dbResponse->ledgerSequence;
+    response["owner"] = ripple::toBase58(dbResponse->owner);
+    response["is_burned"] = dbResponse->isBurned;
+
+    response["flags"] = ripple::nft::getFlags(dbResponse->tokenID);
+    response["transfer_fee"] = ripple::nft::getTransferFee(dbResponse->tokenID);
+    response["issuer"] =
+        ripple::toBase58(ripple::nft::getIssuer(dbResponse->tokenID));
+    response["nft_taxon"] =
+        ripple::nft::toUInt32(ripple::nft::getTaxon(dbResponse->tokenID));
+    response["nft_sequence"] = ripple::nft::getSerial(dbResponse->tokenID);
+
+    if (!dbResponse->isBurned)
+    {
+        auto const maybeURI = getURI(*dbResponse, context);
+        // An error occurred
+        if (Status const* status = std::get_if<Status>(&maybeURI))
+            return *status;
+        // A URI was found
+        if (std::string const* uri = std::get_if<std::string>(&maybeURI))
+            response["uri"] = *uri;
+        // A URI was not found, explicitly set to null
+        else
+            response["uri"] = nullptr;
+    }
+
+    return response;
+}
+
+}  // namespace RPC

src/rpc/handlers/NFTOffers.cpp

@@ -0,0 +1,178 @@
+#include <ripple/app/ledger/Ledger.h>
+#include <ripple/basics/StringUtilities.h>
+#include <ripple/protocol/ErrorCodes.h>
+#include <ripple/protocol/Indexes.h>
+#include <ripple/protocol/STLedgerEntry.h>
+#include <ripple/protocol/jss.h>
+#include <boost/json.hpp>
+#include <algorithm>
+#include <rpc/RPCHelpers.h>
+
+namespace RPC {
+
+static void
+appendNftOfferJson(ripple::SLE const& offer, boost::json::array& offers)
+{
+    offers.push_back(boost::json::object_kind);
+    boost::json::object& obj(offers.back().as_object());
+
+    obj[JS(index)] = ripple::to_string(offer.key());
+    obj[JS(flags)] = (offer)[ripple::sfFlags];
+    obj[JS(owner)] = ripple::toBase58(offer.getAccountID(ripple::sfOwner));
+
+    if (offer.isFieldPresent(ripple::sfDestination))
+        obj[JS(destination)] =
+            ripple::toBase58(offer.getAccountID(ripple::sfDestination));
+
+    if (offer.isFieldPresent(ripple::sfExpiration))
+        obj[JS(expiration)] = offer.getFieldU32(ripple::sfExpiration);
+
+    obj[JS(amount)] = toBoostJson(offer.getFieldAmount(ripple::sfAmount)
+                                      .getJson(ripple::JsonOptions::none));
+}
+
+static Result
+enumerateNFTOffers(
+    Context const& context,
+    ripple::uint256 const& tokenid,
+    ripple::Keylet const& directory)
+{
+    auto const& request = context.params;
+
+    auto v = ledgerInfoFromRequest(context);
+    if (auto status = std::get_if<Status>(&v))
+        return *status;
+
+    auto lgrInfo = std::get<ripple::LedgerInfo>(v);
+
+    // TODO: just check for existence without pulling
+    if (!context.backend->fetchLedgerObject(
+            directory.key, lgrInfo.seq, context.yield))
+        return Status{Error::rpcOBJECT_NOT_FOUND, "notFound"};
+
+    std::uint32_t limit;
+    if (auto const status = getLimit(context, limit); status)
+        return status;
+
+    boost::json::object response = {};
+    response[JS(nft_id)] = ripple::to_string(tokenid);
+    response[JS(offers)] = boost::json::value(boost::json::array_kind);
+
+    auto& jsonOffers = response[JS(offers)].as_array();
+
+    std::vector<ripple::SLE> offers;
+    std::uint64_t reserve(limit);
+    ripple::uint256 cursor;
+
+    if (request.contains(JS(marker)))
+    {
+        // We have a start point. Use limit - 1 from the result and use the
+        // very last one for the resume.
+        auto const& marker(request.at(JS(marker)));
+
+        if (!marker.is_string())
+            return Status{Error::rpcINVALID_PARAMS, "markerNotString"};
+
+        if (!cursor.parseHex(marker.as_string().c_str()))
+            return Status{Error::rpcINVALID_PARAMS, "malformedCursor"};
+
+        auto const sle =
+            read(ripple::keylet::nftoffer(cursor), lgrInfo, context);
+
+        if (!sle || tokenid != sle->getFieldH256(ripple::sfNFTokenID))
+            return Status{Error::rpcOBJECT_NOT_FOUND, "notFound"};
+
+        if (tokenid != sle->getFieldH256(ripple::sfNFTokenID))
+            return Status{Error::rpcINVALID_PARAMS, "invalidTokenid"};
+
+        appendNftOfferJson(*sle, jsonOffers);
+        offers.reserve(reserve);
+    }
+    else
+    {
+        // We have no start point, limit should be one higher than requested.
+        offers.reserve(++reserve);
+    }
+
+    auto result = traverseOwnedNodes(
+        *context.backend,
+        directory,
+        cursor,
+        0,
+        lgrInfo.seq,
+        limit,
+        {},
+        context.yield,
+        [&offers](ripple::SLE const& offer) {
+            if (offer.getType() == ripple::ltNFTOKEN_OFFER)
+            {
+                offers.emplace_back(offer);
+                return true;
+            }
+
+            return false;
+        });
+
+    if (auto status = std::get_if<RPC::Status>(&result))
+        return *status;
+
+    if (offers.size() == reserve)
+    {
+        response[JS(limit)] = limit;
+        response[JS(marker)] = to_string(offers.back().key());
+        offers.pop_back();
+    }
+
+    for (auto const& offer : offers)
+        appendNftOfferJson(offer, jsonOffers);
+
+    return response;
+}
+
+std::variant<ripple::uint256, Status>
+getTokenid(boost::json::object const& request)
+{
+    if (!request.contains(JS(nft_id)))
+        return Status{Error::rpcINVALID_PARAMS, "missingTokenid"};
+
+    if (!request.at(JS(nft_id)).is_string())
+        return Status{Error::rpcINVALID_PARAMS, "tokenidNotString"};
+
+    ripple::uint256 tokenid;
+    if (!tokenid.parseHex(request.at(JS(nft_id)).as_string().c_str()))
+        return Status{Error::rpcINVALID_PARAMS, "malformedCursor"};
+
+    return tokenid;
+}
+
+Result
+doNFTOffers(Context const& context, bool sells)
+{
+    auto const v = getTokenid(context.params);
+    if (auto const status = std::get_if<Status>(&v))
+        return *status;
+
+    auto const getKeylet = [sells, &v]() {
+        if (sells)
+            return ripple::keylet::nft_sells(std::get<ripple::uint256>(v));
+
+        return ripple::keylet::nft_buys(std::get<ripple::uint256>(v));
+    };
+
+    return enumerateNFTOffers(
+        context, std::get<ripple::uint256>(v), getKeylet());
+}
+
+Result
+doNFTSellOffers(Context const& context)
+{
+    return doNFTOffers(context, true);
+}
+
+Result
+doNFTBuyOffers(Context const& context)
+{
+    return doNFTOffers(context, false);
+}
+
+}  // namespace RPC

src/rpc/handlers/NoRippleCheck.cpp

@@ -10,9 +10,9 @@ getBaseTx(
     ripple::Fees const& fees)
 {
     boost::json::object tx;
-    tx["Sequence"] = accountSeq;
-    tx["Account"] = ripple::toBase58(accountID);
-    tx["Fee"] = RPC::toBoostJson(fees.units.jsonClipped());
+    tx[JS(Sequence)] = accountSeq;
+    tx[JS(Account)] = ripple::toBase58(accountID);
+    tx[JS(Fee)] = RPC::toBoostJson(fees.units.jsonClipped());
     return tx;
 }
 
@@ -21,11 +21,9 @@ doNoRippleCheck(Context const& context)
 {
     auto const& request = context.params;
 
-    auto accountID =
-        accountFromStringStrict(getRequiredString(request, "account"));
-
-    if (!accountID)
-        return Status{Error::rpcINVALID_PARAMS, "malformedAccount"};
+    ripple::AccountID accountID;
+    if (auto const status = getAccount(request, accountID); status)
+        return status;
 
     std::string role = getRequiredString(request, "role");
     bool roleGateway = false;
@@ -36,7 +34,9 @@ doNoRippleCheck(Context const& context)
             return Status{Error::rpcINVALID_PARAMS, "role field is invalid"};
     }
 
-    size_t limit = getUInt(request, "limit", 300);
+    std::uint32_t limit = 300;
+    if (auto const status = getLimit(context, limit); status)
+        return status;
 
     bool includeTxs = getBool(request, "transactions", false);
 
@@ -51,11 +51,11 @@ doNoRippleCheck(Context const& context)
 
     boost::json::array transactions;
 
-    auto keylet = ripple::keylet::account(*accountID);
+    auto keylet = ripple::keylet::account(accountID);
     auto accountObj = context.backend->fetchLedgerObject(
         keylet.key, lgrInfo.seq, context.yield);
     if (!accountObj)
-        throw AccountNotFoundError(ripple::toBase58(*accountID));
+        throw AccountNotFoundError(ripple::toBase58(accountID));
 
     ripple::SerialIter it{accountObj->data(), accountObj->size()};
     ripple::SLE sle{it, keylet.key};
@@ -79,16 +79,16 @@ doNoRippleCheck(Context const& context)
             "You should immediately set your default ripple flag");
         if (includeTxs)
         {
-            auto tx = getBaseTx(*accountID, accountSeq++, *fees);
-            tx["TransactionType"] = "AccountSet";
-            tx["SetFlag"] = 8;
+            auto tx = getBaseTx(accountID, accountSeq++, *fees);
+            tx[JS(TransactionType)] = JS(AccountSet);
+            tx[JS(SetFlag)] = 8;
             transactions.push_back(tx);
         }
     }
 
     traverseOwnedNodes(
         *context.backend,
-        *accountID,
+        accountID,
         lgrInfo.seq,
         std::numeric_limits<std::uint32_t>::max(),
         {},
@@ -141,12 +141,12 @@ doNoRippleCheck(Context const& context)
                         ripple::STAmount limitAmount(ownedItem.getFieldAmount(
                             bLow ? ripple::sfLowLimit : ripple::sfHighLimit));
                         limitAmount.setIssuer(peer);
-                        auto tx = getBaseTx(*accountID, accountSeq++, *fees);
-                        tx["TransactionType"] = "TrustSet";
-                        tx["LimitAmount"] = RPC::toBoostJson(
+                        auto tx = getBaseTx(accountID, accountSeq++, *fees);
+                        tx[JS(TransactionType)] = JS(TrustSet);
+                        tx[JS(LimitAmount)] = RPC::toBoostJson(
                             limitAmount.getJson(ripple::JsonOptions::none));
-                        tx["Flags"] = bNoRipple ? ripple::tfClearNoRipple
-                                                : ripple::tfSetNoRipple;
+                        tx[JS(Flags)] = bNoRipple ? ripple::tfClearNoRipple
+                                                  : ripple::tfSetNoRipple;
                         transactions.push_back(tx);
                     }
 
@@ -158,11 +158,11 @@ doNoRippleCheck(Context const& context)
         });
 
     boost::json::object response;
-    response["ledger_index"] = lgrInfo.seq;
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
+    response[JS(ledger_index)] = lgrInfo.seq;
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
     response["problems"] = std::move(problems);
     if (includeTxs)
-        response["transactions"] = std::move(transactions);
+        response[JS(transactions)] = std::move(transactions);
 
     return response;
 }

src/rpc/handlers/Random.cpp

@@ -1,6 +1,10 @@
+// rngfill.h doesn't compile without this include
+#include <cassert>
+
 #include <ripple/beast/utility/rngfill.h>
 #include <ripple/crypto/csprng.h>
 #include <rpc/RPCHelpers.h>
+
 namespace RPC {
 
 Result
@@ -10,7 +14,8 @@ doRandom(Context const& context)
 
     beast::rngfill(rand.begin(), rand.size(), ripple::crypto_prng());
     boost::json::object result;
-    result["random"] = ripple::strHex(rand);
+    result[JS(random)] = ripple::strHex(rand);
     return result;
 }
+
 }  // namespace RPC

src/rpc/handlers/ServerInfo.cpp

@@ -2,6 +2,7 @@
 #include <backend/BackendInterface.h>
 #include <etl/ETLSource.h>
 #include <etl/ReportingETL.h>
+#include <main/Build.h>
 #include <rpc/RPCHelpers.h>
 
 namespace RPC {
@@ -36,56 +37,68 @@ doServerInfo(Context const& context)
     if (age < 0)
         age = 0;
 
-    response["info"] = boost::json::object{};
-    boost::json::object& info = response["info"].as_object();
+    response[JS(info)] = boost::json::object{};
+    boost::json::object& info = response[JS(info)].as_object();
 
-    info["complete_ledgers"] = std::to_string(range->minSequence) + "-" +
+    info[JS(complete_ledgers)] = std::to_string(range->minSequence) + "-" +
         std::to_string(range->maxSequence);
 
-    info["counters"] = boost::json::object{};
-    info["counters"].as_object()["rpc"] = context.counters.report();
+    bool admin = context.clientIp == "127.0.0.1";
+
+    if (admin)
+    {
+        info[JS(counters)] = boost::json::object{};
+        info[JS(counters)].as_object()[JS(rpc)] = context.counters.report();
+        info[JS(counters)].as_object()["subscriptions"] =
+            context.subscriptions->report();
+    }
 
     auto serverInfoRippled = context.balancer->forwardToRippled(
         {{"command", "server_info"}}, context.clientIp, context.yield);
 
-    info["load_factor"] = 1;
-    if (serverInfoRippled && !serverInfoRippled->contains("error"))
+    info[JS(load_factor)] = 1;
+    info["clio_version"] = Build::getClioVersionString();
+    if (serverInfoRippled && !serverInfoRippled->contains(JS(error)))
     {
         try
         {
-            auto& rippledResult = serverInfoRippled->at("result").as_object();
-            auto& rippledInfo = rippledResult.at("info").as_object();
-            info["load_factor"] = rippledInfo["load_factor"];
-            info["validation_quorum"] = rippledInfo["validation_quorum"];
+            auto& rippledResult = serverInfoRippled->at(JS(result)).as_object();
+            auto& rippledInfo = rippledResult.at(JS(info)).as_object();
+            info[JS(load_factor)] = rippledInfo[JS(load_factor)];
+            info[JS(validation_quorum)] = rippledInfo[JS(validation_quorum)];
+            info["rippled_version"] = rippledInfo[JS(build_version)];
         }
         catch (std::exception const&)
         {
         }
     }
 
-    info["validated_ledger"] = boost::json::object{};
-    boost::json::object& validated = info["validated_ledger"].as_object();
+    info[JS(validated_ledger)] = boost::json::object{};
+    boost::json::object& validated = info[JS(validated_ledger)].as_object();
 
-    validated["age"] = age;
-    validated["hash"] = ripple::strHex(lgrInfo->hash);
-    validated["seq"] = lgrInfo->seq;
-    validated["base_fee_xrp"] = fees->base.decimalXRP();
-    validated["reserve_base_xrp"] = fees->reserve.decimalXRP();
-    validated["reserve_inc_xrp"] = fees->increment.decimalXRP();
+    validated[JS(age)] = age;
+    validated[JS(hash)] = ripple::strHex(lgrInfo->hash);
+    validated[JS(seq)] = lgrInfo->seq;
+    validated[JS(base_fee_xrp)] = fees->base.decimalXRP();
+    validated[JS(reserve_base_xrp)] = fees->reserve.decimalXRP();
+    validated[JS(reserve_inc_xrp)] = fees->increment.decimalXRP();
 
-    response["cache"] = boost::json::object{};
-    auto& cache = response["cache"].as_object();
+    info["cache"] = boost::json::object{};
+    auto& cache = info["cache"].as_object();
 
     cache["size"] = context.backend->cache().size();
     cache["is_full"] = context.backend->cache().isFull();
     cache["latest_ledger_seq"] =
         context.backend->cache().latestLedgerSequence();
+    cache["object_hit_rate"] = context.backend->cache().getObjectHitRate();
+    cache["successor_hit_rate"] =
+        context.backend->cache().getSuccessorHitRate();
 
-    response["etl"] = context.etl->getInfo();
+    if (admin)
+    {
+        info["etl"] = context.etl->getInfo();
+    }
 
-    response["note"] =
-        "This is a clio server. If you want to talk to rippled, include "
-        "\"ledger_index\":\"current\" in your request";
     return response;
 }
 }  // namespace RPC

src/rpc/handlers/Subscribe.cpp

@@ -17,7 +17,7 @@ static std::unordered_set<std::string> validCommonStreams{
 Status
 validateStreams(boost::json::object const& request)
 {
-    boost::json::array const& streams = request.at("streams").as_array();
+    boost::json::array const& streams = request.at(JS(streams)).as_array();
 
     for (auto const& stream : streams)
     {
@@ -40,7 +40,7 @@ subscribeToStreams(
     std::shared_ptr<WsBase> session,
     SubscriptionManager& manager)
 {
-    boost::json::array const& streams = request.at("streams").as_array();
+    boost::json::array const& streams = request.at(JS(streams)).as_array();
 
     boost::json::object response;
     for (auto const& stream : streams)
@@ -69,7 +69,7 @@ unsubscribeToStreams(
     std::shared_ptr<WsBase> session,
     SubscriptionManager& manager)
 {
-    boost::json::array const& streams = request.at("streams").as_array();
+    boost::json::array const& streams = request.at(JS(streams)).as_array();
 
     for (auto const& stream : streams)
     {
@@ -114,7 +114,7 @@ subscribeToAccounts(
     std::shared_ptr<WsBase> session,
     SubscriptionManager& manager)
 {
-    boost::json::array const& accounts = request.at("accounts").as_array();
+    boost::json::array const& accounts = request.at(JS(accounts)).as_array();
 
     for (auto const& account : accounts)
     {
@@ -138,7 +138,7 @@ unsubscribeToAccounts(
     std::shared_ptr<WsBase> session,
     SubscriptionManager& manager)
 {
-    boost::json::array const& accounts = request.at("accounts").as_array();
+    boost::json::array const& accounts = request.at(JS(accounts)).as_array();
 
     for (auto const& account : accounts)
     {
@@ -163,7 +163,7 @@ subscribeToAccountsProposed(
     SubscriptionManager& manager)
 {
     boost::json::array const& accounts =
-        request.at("accounts_proposed").as_array();
+        request.at(JS(accounts_proposed)).as_array();
 
     for (auto const& account : accounts)
     {
@@ -188,7 +188,7 @@ unsubscribeToAccountsProposed(
     SubscriptionManager& manager)
 {
     boost::json::array const& accounts =
-        request.at("accounts_proposed").as_array();
+        request.at(JS(accounts_proposed)).as_array();
 
     for (auto const& account : accounts)
     {
@@ -212,68 +212,57 @@ validateAndGetBooks(
     boost::json::object const& request,
     std::shared_ptr<Backend::BackendInterface const> const& backend)
 {
-    if (!request.at("books").is_array())
+    if (!request.at(JS(books)).is_array())
         return Status{Error::rpcINVALID_PARAMS, "booksNotArray"};
-    boost::json::array const& books = request.at("books").as_array();
+    boost::json::array const& books = request.at(JS(books)).as_array();
 
     std::vector<ripple::Book> booksToSub;
     std::optional<Backend::LedgerRange> rng;
     boost::json::array snapshot;
     for (auto const& book : books)
     {
-        auto parsed = parseBook(book.as_object());
-        if (auto status = std::get_if<Status>(&parsed))
+        auto parsedBook = parseBook(book.as_object());
+        if (auto status = std::get_if<Status>(&parsedBook))
             return *status;
-        else
+
+        auto b = std::get<ripple::Book>(parsedBook);
+        booksToSub.push_back(b);
+        bool both = book.as_object().contains(JS(both));
+        if (both)
+            booksToSub.push_back(ripple::reversed(b));
+
+        if (book.as_object().contains(JS(snapshot)))
         {
-            auto b = std::get<ripple::Book>(parsed);
-            booksToSub.push_back(b);
-            bool both = book.as_object().contains("both");
+            if (!rng)
+                rng = backend->fetchLedgerRange();
+            ripple::AccountID takerID = beast::zero;
+            if (book.as_object().contains(JS(taker)))
+                if (auto const status = getTaker(book.as_object(), takerID);
+                    status)
+                    return status;
+
+            auto getOrderBook = [&snapshot, &backend, &rng, &takerID](
+                                    auto book,
+                                    boost::asio::yield_context& yield) {
+                auto bookBase = getBookBase(book);
+                auto [offers, retMarker] = backend->fetchBookOffers(
+                    bookBase, rng->maxSequence, 200, {}, yield);
+
+                auto orderBook = postProcessOrderBook(
+                    offers, book, takerID, *backend, rng->maxSequence, yield);
+                std::copy(
+                    orderBook.begin(),
+                    orderBook.end(),
+                    std::back_inserter(snapshot));
+            };
+            getOrderBook(b, yield);
             if (both)
-                booksToSub.push_back(ripple::reversed(b));
-
-            if (book.as_object().contains("snapshot"))
-            {
-                if (!rng)
-                    rng = backend->fetchLedgerRange();
-                ripple::AccountID takerID = beast::zero;
-                if (book.as_object().contains("taker"))
-                {
-                    auto parsed = parseTaker(request.at("taker"));
-                    if (auto status = std::get_if<Status>(&parsed))
-                        return *status;
-                    else
-                    {
-                        takerID = std::get<ripple::AccountID>(parsed);
-                    }
-                }
-                auto getOrderBook = [&snapshot, &backend, &rng, &takerID](
-                                        auto book,
-                                        boost::asio::yield_context& yield) {
-                    auto bookBase = getBookBase(book);
-                    auto [offers, retCursor] = backend->fetchBookOffers(
-                        bookBase, rng->maxSequence, 200, {}, yield);
-
-                    auto orderBook = postProcessOrderBook(
-                        offers,
-                        book,
-                        takerID,
-                        *backend,
-                        rng->maxSequence,
-                        yield);
-                    std::copy(
-                        orderBook.begin(),
-                        orderBook.end(),
-                        std::back_inserter(snapshot));
-                };
-                getOrderBook(b, yield);
-                if (both)
-                    getOrderBook(ripple::reversed(b), yield);
-            }
+                getOrderBook(ripple::reversed(b), yield);
         }
     }
     return std::make_pair(booksToSub, snapshot);
 }
+
 void
 subscribeToBooks(
     std::vector<ripple::Book> const& books,
@@ -285,14 +274,33 @@ subscribeToBooks(
         manager.subBook(book, session);
     }
 }
+
+void
+unsubscribeToBooks(
+    std::vector<ripple::Book> const& books,
+    std::shared_ptr<WsBase> session,
+    SubscriptionManager& manager)
+{
+    for (auto const& book : books)
+    {
+        manager.unsubBook(book, session);
+    }
+}
+
 Result
 doSubscribe(Context const& context)
 {
     auto request = context.params;
 
-    if (request.contains("streams"))
+    if (!request.contains(JS(streams)) && !request.contains(JS(accounts)) &&
+        !request.contains(JS(accounts_proposed)) &&
+        !request.contains(JS(books)))
+        return Status{
+            Error::rpcINVALID_PARAMS, "does not contain valid subscription"};
+
+    if (request.contains(JS(streams)))
     {
-        if (!request.at("streams").is_array())
+        if (!request.at(JS(streams)).is_array())
             return Status{Error::rpcINVALID_PARAMS, "streamsNotArray"};
 
         auto status = validateStreams(request);
@@ -301,33 +309,34 @@ doSubscribe(Context const& context)
             return status;
     }
 
-    if (request.contains("accounts"))
+    if (request.contains(JS(accounts)))
     {
-        if (!request.at("accounts").is_array())
+        if (!request.at(JS(accounts)).is_array())
             return Status{Error::rpcINVALID_PARAMS, "accountsNotArray"};
 
-        boost::json::array accounts = request.at("accounts").as_array();
+        boost::json::array accounts = request.at(JS(accounts)).as_array();
         auto status = validateAccounts(accounts);
 
         if (status)
             return status;
     }
 
-    if (request.contains("accounts_proposed"))
+    if (request.contains(JS(accounts_proposed)))
     {
-        if (!request.at("accounts_proposed").is_array())
+        if (!request.at(JS(accounts_proposed)).is_array())
             return Status{Error::rpcINVALID_PARAMS, "accountsProposedNotArray"};
 
         boost::json::array accounts =
-            request.at("accounts_proposed").as_array();
+            request.at(JS(accounts_proposed)).as_array();
         auto status = validateAccounts(accounts);
 
         if (status)
             return status;
     }
+
     std::vector<ripple::Book> books;
     boost::json::array snapshot;
-    if (request.contains("books"))
+    if (request.contains(JS(books)))
     {
         auto parsed =
             validateAndGetBooks(context.yield, request, context.backend);
@@ -341,22 +350,22 @@ doSubscribe(Context const& context)
     }
 
     boost::json::object response;
-    if (request.contains("streams"))
+    if (request.contains(JS(streams)))
         response = subscribeToStreams(
             context.yield, request, context.session, *context.subscriptions);
 
-    if (request.contains("accounts"))
+    if (request.contains(JS(accounts)))
         subscribeToAccounts(request, context.session, *context.subscriptions);
 
-    if (request.contains("accounts_proposed"))
+    if (request.contains(JS(accounts_proposed)))
         subscribeToAccountsProposed(
             request, context.session, *context.subscriptions);
 
-    if (request.contains("books"))
+    if (request.contains(JS(books)))
         subscribeToBooks(books, context.session, *context.subscriptions);
 
     if (snapshot.size())
-        response["offers"] = snapshot;
+        response[JS(offers)] = snapshot;
     return response;
 }
 
@@ -365,9 +374,15 @@ doUnsubscribe(Context const& context)
 {
     auto request = context.params;
 
-    if (request.contains("streams"))
+    if (!request.contains(JS(streams)) && !request.contains(JS(accounts)) &&
+        !request.contains(JS(accounts_proposed)) &&
+        !request.contains(JS(books)))
+        return Status{
+            Error::rpcINVALID_PARAMS, "does not contain valid subscription"};
+
+    if (request.contains(JS(streams)))
     {
-        if (!request.at("streams").is_array())
+        if (!request.at(JS(streams)).is_array())
             return Status{Error::rpcINVALID_PARAMS, "streamsNotArray"};
 
         auto status = validateStreams(request);
@@ -376,41 +391,60 @@ doUnsubscribe(Context const& context)
             return status;
     }
 
-    if (request.contains("accounts"))
+    if (request.contains(JS(accounts)))
     {
-        if (!request.at("accounts").is_array())
+        if (!request.at(JS(accounts)).is_array())
             return Status{Error::rpcINVALID_PARAMS, "accountsNotArray"};
 
-        boost::json::array accounts = request.at("accounts").as_array();
+        boost::json::array accounts = request.at(JS(accounts)).as_array();
         auto status = validateAccounts(accounts);
 
         if (status)
             return status;
     }
 
-    if (request.contains("accounts_proposed"))
+    if (request.contains(JS(accounts_proposed)))
     {
-        if (!request.at("accounts_proposed").is_array())
+        if (!request.at(JS(accounts_proposed)).is_array())
             return Status{Error::rpcINVALID_PARAMS, "accountsProposedNotArray"};
 
         boost::json::array accounts =
-            request.at("accounts_proposed").as_array();
+            request.at(JS(accounts_proposed)).as_array();
         auto status = validateAccounts(accounts);
 
         if (status)
             return status;
     }
 
-    if (request.contains("streams"))
+    std::vector<ripple::Book> books;
+    if (request.contains(JS(books)))
+    {
+        auto parsed =
+            validateAndGetBooks(context.yield, request, context.backend);
+
+        if (auto status = std::get_if<Status>(&parsed))
+            return *status;
+
+        auto [bks, snap] =
+            std::get<std::pair<std::vector<ripple::Book>, boost::json::array>>(
+                parsed);
+
+        books = std::move(bks);
+    }
+
+    if (request.contains(JS(streams)))
         unsubscribeToStreams(request, context.session, *context.subscriptions);
 
-    if (request.contains("accounts"))
+    if (request.contains(JS(accounts)))
         unsubscribeToAccounts(request, context.session, *context.subscriptions);
 
-    if (request.contains("accounts_proposed"))
+    if (request.contains(JS(accounts_proposed)))
         unsubscribeToAccountsProposed(
             request, context.session, *context.subscriptions);
 
+    if (request.contains("books"))
+        unsubscribeToBooks(books, context.session, *context.subscriptions);
+
     boost::json::object response = {{"status", "success"}};
     return response;
 }

src/rpc/handlers/TransactionEntry.cpp

@@ -13,7 +13,7 @@ doTransactionEntry(Context const& context)
     auto lgrInfo = std::get<ripple::LedgerInfo>(v);
 
     ripple::uint256 hash;
-    if (!hash.parseHex(getRequiredString(context.params, "tx_hash")))
+    if (!hash.parseHex(getRequiredString(context.params, JS(tx_hash))))
         return Status{Error::rpcINVALID_PARAMS, "malformedTransaction"};
 
     auto dbResponse = context.backend->fetchTransaction(hash, context.yield);
@@ -33,10 +33,10 @@ doTransactionEntry(Context const& context)
             "Transaction not found."};
 
     auto [txn, meta] = toExpandedJson(*dbResponse);
-    response["tx_json"] = std::move(txn);
-    response["metadata"] = std::move(meta);
-    response["ledger_index"] = lgrInfo.seq;
-    response["ledger_hash"] = ripple::strHex(lgrInfo.hash);
+    response[JS(tx_json)] = std::move(txn);
+    response[JS(metadata)] = std::move(meta);
+    response[JS(ledger_index)] = lgrInfo.seq;
+    response[JS(ledger_hash)] = ripple::strHex(lgrInfo.hash);
     return response;
 }
 

src/rpc/handlers/Tx.cpp

@@ -14,23 +14,23 @@ doTx(Context const& context)
     auto request = context.params;
     boost::json::object response = {};
 
-    if (!request.contains("transaction"))
+    if (!request.contains(JS(transaction)))
         return Status{Error::rpcINVALID_PARAMS, "specifyTransaction"};
 
-    if (!request.at("transaction").is_string())
+    if (!request.at(JS(transaction)).is_string())
         return Status{Error::rpcINVALID_PARAMS, "transactionNotString"};
 
     ripple::uint256 hash;
-    if (!hash.parseHex(request.at("transaction").as_string().c_str()))
+    if (!hash.parseHex(request.at(JS(transaction)).as_string().c_str()))
         return Status{Error::rpcINVALID_PARAMS, "malformedTransaction"};
 
     bool binary = false;
-    if (request.contains("binary"))
+    if (request.contains(JS(binary)))
     {
-        if (!request.at("binary").is_bool())
+        if (!request.at(JS(binary)).is_bool())
             return Status{Error::rpcINVALID_PARAMS, "binaryFlagNotBool"};
 
-        binary = request.at("binary").as_bool();
+        binary = request.at(JS(binary)).as_bool();
     }
 
     auto range = context.backend->fetchLedgerRange();
@@ -45,16 +45,16 @@ doTx(Context const& context)
     {
         auto [txn, meta] = toExpandedJson(*dbResponse);
         response = txn;
-        response["meta"] = meta;
+        response[JS(meta)] = meta;
     }
     else
     {
-        response["tx"] = ripple::strHex(dbResponse->transaction);
-        response["meta"] = ripple::strHex(dbResponse->metadata);
-        response["hash"] = std::move(request.at("transaction").as_string());
+        response[JS(tx)] = ripple::strHex(dbResponse->transaction);
+        response[JS(meta)] = ripple::strHex(dbResponse->metadata);
+        response[JS(hash)] = std::move(request.at(JS(transaction)).as_string());
     }
-    response["date"] = dbResponse->date;
-    response["ledger_index"] = dbResponse->ledgerSequence;
+    response[JS(date)] = dbResponse->date;
+    response[JS(ledger_index)] = dbResponse->ledgerSequence;
 
     return response;
 }

src/subscriptions/Message.h

@@ -0,0 +1,40 @@
+#ifndef CLIO_SUBSCRIPTION_MESSAGE_H
+#define CLIO_SUBSCRIPTION_MESSAGE_H
+
+#include <string>
+
+// This class should only be constructed once, then it can
+// be read from in parallel by many websocket senders
+class Message
+{
+    std::string message_;
+
+public:
+    Message() = delete;
+    Message(std::string&& message) : message_(std::move(message))
+    {
+    }
+
+    Message(Message const&) = delete;
+    Message(Message&&) = delete;
+    Message&
+    operator=(Message const&) = delete;
+    Message&
+    operator=(Message&&) = delete;
+
+    ~Message() = default;
+
+    char*
+    data()
+    {
+        return message_.data();
+    }
+
+    std::size_t
+    size()
+    {
+        return message_.size();
+    }
+};
+
+#endif  // CLIO_SUBSCRIPTION_MESSAGE_H

src/subscriptions/SubscriptionManager.cpp

@@ -5,25 +5,24 @@
 template <class T>
 inline void
 sendToSubscribers(
-    std::string const& message,
+    std::shared_ptr<Message> const& message,
     T& subscribers,
-    boost::asio::io_context::strand& strand)
+    std::atomic_uint64_t& counter)
 {
-    boost::asio::post(strand, [&subscribers, message]() {
-        for (auto it = subscribers.begin(); it != subscribers.end();)
+    for (auto it = subscribers.begin(); it != subscribers.end();)
+    {
+        auto& session = *it;
+        if (session->dead())
         {
-            auto& session = *it;
-            if (session->dead())
-            {
-                it = subscribers.erase(it);
-            }
-            else
-            {
-                session->send(message);
-                ++it;
-            }
+            it = subscribers.erase(it);
+            --counter;
         }
-    });
+        else
+        {
+            session->send(message);
+            ++it;
+        }
+    }
 }
 
 template <class T>
@@ -31,11 +30,13 @@ inline void
 addSession(
     std::shared_ptr<WsBase> session,
     T& subscribers,
-    boost::asio::io_context::strand& strand)
+    std::atomic_uint64_t& counter)
 {
-    boost::asio::post(strand, [&subscribers, s = std::move(session)]() {
-        subscribers.emplace(s);
-    });
+    if (!subscribers.contains(session))
+    {
+        subscribers.insert(session);
+        ++counter;
+    }
 }
 
 template <class T>
@@ -43,29 +44,37 @@ inline void
 removeSession(
     std::shared_ptr<WsBase> session,
     T& subscribers,
-    boost::asio::io_context::strand& strand)
+    std::atomic_uint64_t& counter)
 {
-    boost::asio::post(strand, [&subscribers, s = std::move(session)]() {
-        subscribers.erase(s);
-    });
+    if (subscribers.contains(session))
+    {
+        subscribers.erase(session);
+        --counter;
+    }
 }
 
 void
 Subscription::subscribe(std::shared_ptr<WsBase> const& session)
 {
-    addSession(session, subscribers_, strand_);
+    boost::asio::post(strand_, [this, session]() {
+        addSession(session, subscribers_, subCount_);
+    });
 }
 
 void
 Subscription::unsubscribe(std::shared_ptr<WsBase> const& session)
 {
-    removeSession(session, subscribers_, strand_);
+    boost::asio::post(strand_, [this, session]() {
+        removeSession(session, subscribers_, subCount_);
+    });
 }
 
 void
-Subscription::publish(std::string const& message)
+Subscription::publish(std::shared_ptr<Message>& message)
 {
-    sendToSubscribers(message, subscribers_, strand_);
+    boost::asio::post(strand_, [this, message]() {
+        sendToSubscribers(message, subscribers_, subCount_);
+    });
 }
 
 template <class Key>
@@ -74,7 +83,9 @@ SubscriptionMap<Key>::subscribe(
     std::shared_ptr<WsBase> const& session,
     Key const& account)
 {
-    addSession(session, subscribers_[account], strand_);
+    boost::asio::post(strand_, [this, session, account]() {
+        addSession(session, subscribers_[account], subCount_);
+    });
 }
 
 template <class Key>
@@ -83,14 +94,36 @@ SubscriptionMap<Key>::unsubscribe(
     std::shared_ptr<WsBase> const& session,
     Key const& account)
 {
-    removeSession(session, subscribers_[account], strand_);
+    boost::asio::post(strand_, [this, account, session]() {
+        if (!subscribers_.contains(account))
+            return;
+
+        if (!subscribers_[account].contains(session))
+            return;
+
+        --subCount_;
+
+        subscribers_[account].erase(session);
+
+        if (subscribers_[account].size() == 0)
+        {
+            subscribers_.erase(account);
+        }
+    });
 }
 
 template <class Key>
 void
-SubscriptionMap<Key>::publish(std::string const& message, Key const& account)
+SubscriptionMap<Key>::publish(
+    std::shared_ptr<Message>& message,
+    Key const& account)
 {
-    sendToSubscribers(message, subscribers_[account], strand_);
+    boost::asio::post(strand_, [this, account, message]() {
+        if (!subscribers_.contains(account))
+            return;
+
+        sendToSubscribers(message, subscribers_[account], subCount_);
+    });
 }
 
 boost::json::object
@@ -120,7 +153,7 @@ getLedgerPubMessage(
 boost::json::object
 SubscriptionManager::subLedger(
     boost::asio::yield_context& yield,
-    std::shared_ptr<WsBase>& session)
+    std::shared_ptr<WsBase> session)
 {
     ledgerSubscribers_.subscribe(session);
 
@@ -144,19 +177,19 @@ SubscriptionManager::subLedger(
 }
 
 void
-SubscriptionManager::unsubLedger(std::shared_ptr<WsBase>& session)
+SubscriptionManager::unsubLedger(std::shared_ptr<WsBase> session)
 {
     ledgerSubscribers_.unsubscribe(session);
 }
 
 void
-SubscriptionManager::subTransactions(std::shared_ptr<WsBase>& session)
+SubscriptionManager::subTransactions(std::shared_ptr<WsBase> session)
 {
     txSubscribers_.subscribe(session);
 }
 
 void
-SubscriptionManager::unsubTransactions(std::shared_ptr<WsBase>& session)
+SubscriptionManager::unsubTransactions(std::shared_ptr<WsBase> session)
 {
     txSubscribers_.unsubscribe(session);
 }
@@ -167,6 +200,11 @@ SubscriptionManager::subAccount(
     std::shared_ptr<WsBase>& session)
 {
     accountSubscribers_.subscribe(session, account);
+
+    std::unique_lock lk(cleanupMtx_);
+    cleanupFuncs_[session].emplace_back([this, account](session_ptr session) {
+        unsubAccount(account, session);
+    });
 }
 
 void
@@ -180,15 +218,19 @@ SubscriptionManager::unsubAccount(
 void
 SubscriptionManager::subBook(
     ripple::Book const& book,
-    std::shared_ptr<WsBase>& session)
+    std::shared_ptr<WsBase> session)
 {
     bookSubscribers_.subscribe(session, book);
+
+    std::unique_lock lk(cleanupMtx_);
+    cleanupFuncs_[session].emplace_back(
+        [this, book](session_ptr session) { unsubBook(book, session); });
 }
 
 void
 SubscriptionManager::unsubBook(
     ripple::Book const& book,
-    std::shared_ptr<WsBase>& session)
+    std::shared_ptr<WsBase> session)
 {
     bookSubscribers_.unsubscribe(session, book);
 }
@@ -200,8 +242,10 @@ SubscriptionManager::pubLedger(
     std::string const& ledgerRange,
     std::uint32_t txnCount)
 {
-    ledgerSubscribers_.publish(boost::json::serialize(
+    auto message = std::make_shared<Message>(boost::json::serialize(
         getLedgerPubMessage(lgrInfo, fees, ledgerRange, txnCount)));
+
+    ledgerSubscribers_.publish(message);
 }
 
 void
@@ -213,7 +257,8 @@ SubscriptionManager::pubTransaction(
     boost::json::object pubObj;
     pubObj["transaction"] = RPC::toJson(*tx);
     pubObj["meta"] = RPC::toJson(*meta);
-    RPC::insertDeliveredAmount(pubObj["meta"].as_object(), tx, meta);
+    RPC::insertDeliveredAmount(
+        pubObj["meta"].as_object(), tx, meta, blobs.date);
     pubObj["type"] = "transaction";
     pubObj["validated"] = true;
     pubObj["status"] = "closed";
@@ -250,10 +295,9 @@ SubscriptionManager::pubTransaction(
         }
     }
 
-    std::string pubMsg{boost::json::serialize(pubObj)};
+    auto pubMsg = std::make_shared<Message>(boost::json::serialize(pubObj));
     txSubscribers_.publish(pubMsg);
 
-    auto journal = ripple::debugLog();
     auto accounts = meta->getAffectedAccounts();
 
     for (auto const& account : accounts)
@@ -305,7 +349,7 @@ void
 SubscriptionManager::forwardProposedTransaction(
     boost::json::object const& response)
 {
-    std::string pubMsg{boost::json::serialize(response)};
+    auto pubMsg = std::make_shared<Message>(boost::json::serialize(response));
     txProposedSubscribers_.publish(pubMsg);
 
     auto transaction = response.at("transaction").as_object();
@@ -318,45 +362,45 @@ SubscriptionManager::forwardProposedTransaction(
 void
 SubscriptionManager::forwardManifest(boost::json::object const& response)
 {
-    std::string pubMsg{boost::json::serialize(response)};
+    auto pubMsg = std::make_shared<Message>(boost::json::serialize(response));
     manifestSubscribers_.publish(pubMsg);
 }
 
 void
 SubscriptionManager::forwardValidation(boost::json::object const& response)
 {
-    std::string pubMsg{boost::json::serialize(response)};
-    validationsSubscribers_.publish(std::move(pubMsg));
+    auto pubMsg = std::make_shared<Message>(boost::json::serialize(response));
+    validationsSubscribers_.publish(pubMsg);
 }
 
 void
 SubscriptionManager::subProposedAccount(
     ripple::AccountID const& account,
-    std::shared_ptr<WsBase>& session)
+    std::shared_ptr<WsBase> session)
 {
     accountProposedSubscribers_.subscribe(session, account);
 }
 
 void
-SubscriptionManager::subManifest(std::shared_ptr<WsBase>& session)
+SubscriptionManager::subManifest(std::shared_ptr<WsBase> session)
 {
     manifestSubscribers_.subscribe(session);
 }
 
 void
-SubscriptionManager::unsubManifest(std::shared_ptr<WsBase>& session)
+SubscriptionManager::unsubManifest(std::shared_ptr<WsBase> session)
 {
     manifestSubscribers_.unsubscribe(session);
 }
 
 void
-SubscriptionManager::subValidation(std::shared_ptr<WsBase>& session)
+SubscriptionManager::subValidation(std::shared_ptr<WsBase> session)
 {
     validationsSubscribers_.subscribe(session);
 }
 
 void
-SubscriptionManager::unsubValidation(std::shared_ptr<WsBase>& session)
+SubscriptionManager::unsubValidation(std::shared_ptr<WsBase> session)
 {
     validationsSubscribers_.unsubscribe(session);
 }
@@ -364,19 +408,34 @@ SubscriptionManager::unsubValidation(std::shared_ptr<WsBase>& session)
 void
 SubscriptionManager::unsubProposedAccount(
     ripple::AccountID const& account,
-    std::shared_ptr<WsBase>& session)
+    std::shared_ptr<WsBase> session)
 {
     accountProposedSubscribers_.unsubscribe(session, account);
 }
 
 void
-SubscriptionManager::subProposedTransactions(std::shared_ptr<WsBase>& session)
+SubscriptionManager::subProposedTransactions(std::shared_ptr<WsBase> session)
 {
     txProposedSubscribers_.subscribe(session);
 }
 
 void
-SubscriptionManager::unsubProposedTransactions(std::shared_ptr<WsBase>& session)
+SubscriptionManager::unsubProposedTransactions(std::shared_ptr<WsBase> session)
 {
     txProposedSubscribers_.unsubscribe(session);
 }
+
+void
+SubscriptionManager::cleanup(std::shared_ptr<WsBase> session)
+{
+    std::unique_lock lk(cleanupMtx_);
+    if (!cleanupFuncs_.contains(session))
+        return;
+
+    for (auto f : cleanupFuncs_[session])
+    {
+        f(session);
+    }
+
+    cleanupFuncs_.erase(session);
+}

src/subscriptions/SubscriptionManager.h

@@ -3,6 +3,7 @@
 
 #include <backend/BackendInterface.h>
 #include <memory>
+#include <subscriptions/Message.h>
 
 class WsBase;
 
@@ -10,6 +11,7 @@ class Subscription
 {
     boost::asio::io_context::strand strand_;
     std::unordered_set<std::shared_ptr<WsBase>> subscribers_ = {};
+    std::atomic_uint64_t subCount_ = 0;
 
 public:
     Subscription() = delete;
@@ -29,16 +31,24 @@ public:
     unsubscribe(std::shared_ptr<WsBase> const& session);
 
     void
-    publish(std::string const& message);
+    publish(std::shared_ptr<Message>& message);
+
+    std::uint64_t
+    count()
+    {
+        return subCount_.load();
+    }
 };
 
 template <class Key>
 class SubscriptionMap
 {
-    using subscribers = std::unordered_set<std::shared_ptr<WsBase>>;
+    using ptr = std::shared_ptr<WsBase>;
+    using subscribers = std::set<ptr>;
 
     boost::asio::io_context::strand strand_;
     std::unordered_map<Key, subscribers> subscribers_ = {};
+    std::atomic_uint64_t subCount_ = 0;
 
 public:
     SubscriptionMap() = delete;
@@ -58,11 +68,19 @@ public:
     unsubscribe(std::shared_ptr<WsBase> const& session, Key const& key);
 
     void
-    publish(std::string const& message, Key const& key);
+    publish(std::shared_ptr<Message>& message, Key const& key);
+
+    std::uint64_t
+    count()
+    {
+        return subCount_.load();
+    }
 };
 
 class SubscriptionManager
 {
+    using session_ptr = std::shared_ptr<WsBase>;
+
     std::vector<std::thread> workers_;
     boost::asio::io_context ioc_;
     std::optional<boost::asio::io_context::work> work_;
@@ -132,9 +150,7 @@ public:
     }
 
     boost::json::object
-    subLedger(
-        boost::asio::yield_context& yield,
-        std::shared_ptr<WsBase>& session);
+    subLedger(boost::asio::yield_context& yield, session_ptr session);
 
     void
     pubLedger(
@@ -144,13 +160,13 @@ public:
         std::uint32_t txnCount);
 
     void
-    unsubLedger(std::shared_ptr<WsBase>& session);
+    unsubLedger(session_ptr session);
 
     void
-    subTransactions(std::shared_ptr<WsBase>& session);
+    subTransactions(session_ptr session);
 
     void
-    unsubTransactions(std::shared_ptr<WsBase>& session);
+    unsubTransactions(session_ptr session);
 
     void
     pubTransaction(
@@ -158,32 +174,28 @@ public:
         ripple::LedgerInfo const& lgrInfo);
 
     void
-    subAccount(
-        ripple::AccountID const& account,
-        std::shared_ptr<WsBase>& session);
+    subAccount(ripple::AccountID const& account, session_ptr& session);
 
     void
-    unsubAccount(
-        ripple::AccountID const& account,
-        std::shared_ptr<WsBase>& session);
+    unsubAccount(ripple::AccountID const& account, session_ptr& session);
 
     void
-    subBook(ripple::Book const& book, std::shared_ptr<WsBase>& session);
+    subBook(ripple::Book const& book, session_ptr session);
 
     void
-    unsubBook(ripple::Book const& book, std::shared_ptr<WsBase>& session);
+    unsubBook(ripple::Book const& book, session_ptr session);
 
     void
-    subManifest(std::shared_ptr<WsBase>& session);
+    subManifest(session_ptr session);
 
     void
-    unsubManifest(std::shared_ptr<WsBase>& session);
+    unsubManifest(session_ptr session);
 
     void
-    subValidation(std::shared_ptr<WsBase>& session);
+    subValidation(session_ptr session);
 
     void
-    unsubValidation(std::shared_ptr<WsBase>& session);
+    unsubValidation(session_ptr session);
 
     void
     forwardProposedTransaction(boost::json::object const& response);
@@ -195,26 +207,51 @@ public:
     forwardValidation(boost::json::object const& response);
 
     void
-    subProposedAccount(
-        ripple::AccountID const& account,
-        std::shared_ptr<WsBase>& session);
+    subProposedAccount(ripple::AccountID const& account, session_ptr session);
 
     void
-    unsubProposedAccount(
-        ripple::AccountID const& account,
-        std::shared_ptr<WsBase>& session);
+    unsubProposedAccount(ripple::AccountID const& account, session_ptr session);
 
     void
-    subProposedTransactions(std::shared_ptr<WsBase>& session);
+    subProposedTransactions(session_ptr session);
 
     void
-    unsubProposedTransactions(std::shared_ptr<WsBase>& session);
+    unsubProposedTransactions(session_ptr session);
+
+    void
+    cleanup(session_ptr session);
+
+    boost::json::object
+    report()
+    {
+        boost::json::object counts = {};
+
+        counts["ledger"] = ledgerSubscribers_.count();
+        counts["transactions"] = txSubscribers_.count();
+        counts["transactions_proposed"] = txProposedSubscribers_.count();
+        counts["manifests"] = manifestSubscribers_.count();
+        counts["validations"] = validationsSubscribers_.count();
+        counts["account"] = accountSubscribers_.count();
+        counts["accounts_proposed"] = accountProposedSubscribers_.count();
+        counts["books"] = bookSubscribers_.count();
+
+        return counts;
+    }
 
 private:
     void
-    sendAll(
-        std::string const& pubMsg,
-        std::unordered_set<std::shared_ptr<WsBase>>& subs);
+    sendAll(std::string const& pubMsg, std::unordered_set<session_ptr>& subs);
+
+    /**
+     * This is how we chose to cleanup subscriptions that have been closed.
+     * Each time we add a subscriber, we add the opposite lambda that
+     * unsubscribes that subscriber when cleanup is called with the session that
+     * closed.
+     */
+    using CleanupFunction = std::function<void(session_ptr)>;
+    std::mutex cleanupMtx_;
+    std::unordered_map<session_ptr, std::vector<CleanupFunction>>
+        cleanupFuncs_ = {};
 };
 
 #endif  // SUBSCRIPTION_MANAGER_H

src/webserver/DOSGuard.h

@@ -15,6 +15,7 @@ class DOSGuard
     std::uint32_t const maxFetches_;
     std::uint32_t const sweepInterval_;
 
+    // Load config setting for DOSGuard
     std::optional<boost::json::object>
     getConfig(boost::json::object const& config) const
     {
@@ -92,6 +93,12 @@ public:
             });
     }
 
+    bool
+    isWhiteListed(std::string const& ip)
+    {
+        return whitelist_.contains(ip);
+    }
+
     bool
     isOk(std::string const& ip)
     {

src/webserver/HttpBase.h

@@ -20,6 +20,7 @@
 
 #include <rpc/Counters.h>
 #include <rpc/RPC.h>
+#include <rpc/WorkQueue.h>
 #include <vector>
 #include <webserver/DOSGuard.h>
 
@@ -92,6 +93,7 @@ class HttpBase
     std::shared_ptr<ReportingETL const> etl_;
     DOSGuard& dosGuard_;
     RPC::Counters& counters_;
+    WorkQueue& workQueue_;
     send_lambda lambda_;
 
 protected:
@@ -146,6 +148,7 @@ public:
         std::shared_ptr<ReportingETL const> etl,
         DOSGuard& dosGuard,
         RPC::Counters& counters,
+        WorkQueue& queue,
         boost::beast::flat_buffer buffer)
         : ioc_(ioc)
         , backend_(backend)
@@ -154,6 +157,7 @@ public:
         , etl_(etl)
         , dosGuard_(dosGuard)
         , counters_(counters)
+        , workQueue_(queue)
         , lambda_(*this)
         , buffer_(std::move(buffer))
     {
@@ -208,7 +212,8 @@ public:
                 balancer_,
                 etl_,
                 dosGuard_,
-                counters_);
+                counters_,
+                workQueue_);
         }
 
         auto ip = derived().ip();
@@ -220,21 +225,36 @@ public:
 
         // Requests are handed using coroutines. Here we spawn a coroutine
         // which will asynchronously handle a request.
-        boost::asio::spawn(
-            derived().stream().get_executor(),
-            [this, ip, session](boost::asio::yield_context yield) {
-                handle_request(
-                    yield,
-                    std::move(req_),
-                    lambda_,
-                    backend_,
-                    balancer_,
-                    etl_,
-                    dosGuard_,
-                    counters_,
-                    *ip,
-                    session);
-            });
+        if (!workQueue_.postCoro(
+                [this, ip, session](boost::asio::yield_context yield) {
+                    handle_request(
+                        yield,
+                        std::move(req_),
+                        lambda_,
+                        backend_,
+                        subscriptions_,
+                        balancer_,
+                        etl_,
+                        dosGuard_,
+                        counters_,
+                        *ip,
+                        session);
+                },
+                dosGuard_.isWhiteListed(*ip)))
+        {
+            // Non-whitelist connection rejected due to full connection queue
+            http::response<http::string_body> res{
+                http::status::ok, req_.version()};
+            res.set(
+                http::field::server,
+                "clio-server-" + Build::getClioVersionString());
+            res.set(http::field::content_type, "application/json");
+            res.keep_alive(req_.keep_alive());
+            res.body() = boost::json::serialize(
+                RPC::make_error(RPC::Error::rpcTOO_BUSY));
+            res.prepare_payload();
+            lambda_(std::move(res));
+        }
     }
 
     void
@@ -275,6 +295,7 @@ handle_request(
         request<Body, boost::beast::http::basic_fields<Allocator>>&& req,
     Send&& send,
     std::shared_ptr<BackendInterface const> backend,
+    std::shared_ptr<SubscriptionManager> subscriptions,
     std::shared_ptr<ETLLoadBalancer> balancer,
     std::shared_ptr<ReportingETL const> etl,
     DOSGuard& dosGuard,
@@ -287,7 +308,9 @@ handle_request(
                                   std::string content_type,
                                   std::string message) {
         http::response<http::string_body> res{status, req.version()};
-        res.set(http::field::server, "xrpl-reporting-server-v0.0.0");
+        res.set(
+            http::field::server,
+            "clio-server-" + Build::getClioVersionString());
         res.set(http::field::content_type, content_type);
         res.keep_alive(req.keep_alive());
         res.body() = std::string(message);
@@ -307,13 +330,13 @@ handle_request(
 
     if (!dosGuard.isOk(ip))
         return send(httpResponse(
-            http::status::ok,
-            "application/json",
-            boost::json::serialize(RPC::make_error(RPC::Error::rpcSLOW_DOWN))));
+            http::status::service_unavailable,
+            "text/plain",
+            "Server is overloaded"));
 
     try
     {
-        BOOST_LOG_TRIVIAL(info) << "Received request: " << req.body();
+        BOOST_LOG_TRIVIAL(debug) << "Received request: " << req.body();
 
         boost::json::object request;
         std::string responseStr = "";
@@ -333,13 +356,6 @@ handle_request(
                     RPC::make_error(RPC::Error::rpcBAD_SYNTAX))));
         }
 
-        if (!dosGuard.isOk(ip))
-            return send(httpResponse(
-                http::status::ok,
-                "application/json",
-                boost::json::serialize(
-                    RPC::make_error(RPC::Error::rpcSLOW_DOWN))));
-
         auto range = backend->fetchLedgerRange();
         if (!range)
             return send(httpResponse(
@@ -349,7 +365,15 @@ handle_request(
                     RPC::make_error(RPC::Error::rpcNOT_READY))));
 
         std::optional<RPC::Context> context = RPC::make_HttpContext(
-            yc, request, backend, nullptr, balancer, etl, *range, counters, ip);
+            yc,
+            request,
+            backend,
+            subscriptions,
+            balancer,
+            etl,
+            *range,
+            counters,
+            ip);
 
         if (!context)
             return send(httpResponse(
@@ -377,7 +401,6 @@ handle_request(
 
             result = error;
 
-            responseStr = boost::json::serialize(response);
             BOOST_LOG_TRIVIAL(debug)
                 << __func__ << " Encountered error: " << responseStr;
         }
@@ -391,13 +414,23 @@ handle_request(
 
             if (!result.contains("error"))
                 result["status"] = "success";
-
-            responseStr = boost::json::serialize(response);
         }
 
+        boost::json::array warnings;
+        warnings.emplace_back(RPC::make_warning(RPC::warnRPC_CLIO));
+        auto lastCloseAge = context->etl->lastCloseAgeSeconds();
+        if (lastCloseAge >= 60)
+            warnings.emplace_back(RPC::make_warning(RPC::warnRPC_OUTDATED));
+        response["warnings"] = warnings;
+        responseStr = boost::json::serialize(response);
         if (!dosGuard.add(ip, responseStr.size()))
-            result["warning"] = "Too many requests";
-
+        {
+            response["warning"] = "load";
+            warnings.emplace_back(RPC::make_warning(RPC::warnRPC_RATE_LIMIT));
+            response["warnings"] = warnings;
+            // reserialize when we need to include this warning
+            responseStr = boost::json::serialize(response);
+        }
         return send(
             httpResponse(http::status::ok, "application/json", responseStr));
     }

src/webserver/HttpSession.h

@@ -25,6 +25,7 @@ public:
         std::shared_ptr<ReportingETL const> etl,
         DOSGuard& dosGuard,
         RPC::Counters& counters,
+        WorkQueue& queue,
         boost::beast::flat_buffer buffer)
         : HttpBase<HttpSession>(
               ioc,
@@ -34,6 +35,7 @@ public:
               etl,
               dosGuard,
               counters,
+              queue,
               std::move(buffer))
         , stream_(std::move(socket))
     {

src/webserver/Listener.h

@@ -30,6 +30,7 @@ class Detector
     std::shared_ptr<ReportingETL const> etl_;
     DOSGuard& dosGuard_;
     RPC::Counters& counters_;
+    WorkQueue& queue_;
     boost::beast::flat_buffer buffer_;
 
 public:
@@ -42,7 +43,8 @@ public:
         std::shared_ptr<ETLLoadBalancer> balancer,
         std::shared_ptr<ReportingETL const> etl,
         DOSGuard& dosGuard,
-        RPC::Counters& counters)
+        RPC::Counters& counters,
+        WorkQueue& queue)
         : ioc_(ioc)
         , stream_(std::move(socket))
         , ctx_(ctx)
@@ -52,6 +54,7 @@ public:
         , etl_(etl)
         , dosGuard_(dosGuard)
         , counters_(counters)
+        , queue_(queue)
     {
     }
 
@@ -101,6 +104,7 @@ public:
                 etl_,
                 dosGuard_,
                 counters_,
+                queue_,
                 std::move(buffer_))
                 ->run();
             return;
@@ -116,6 +120,7 @@ public:
             etl_,
             dosGuard_,
             counters_,
+            queue_,
             std::move(buffer_))
             ->run();
     }
@@ -132,7 +137,8 @@ make_websocket_session(
     std::shared_ptr<ETLLoadBalancer> balancer,
     std::shared_ptr<ReportingETL const> etl,
     DOSGuard& dosGuard,
-    RPC::Counters& counters)
+    RPC::Counters& counters,
+    WorkQueue& queue)
 {
     std::make_shared<WsUpgrader>(
         ioc,
@@ -143,6 +149,7 @@ make_websocket_session(
         etl,
         dosGuard,
         counters,
+        queue,
         std::move(buffer),
         std::move(req))
         ->run();
@@ -159,7 +166,8 @@ make_websocket_session(
     std::shared_ptr<ETLLoadBalancer> balancer,
     std::shared_ptr<ReportingETL const> etl,
     DOSGuard& dosGuard,
-    RPC::Counters& counters)
+    RPC::Counters& counters,
+    WorkQueue& queue)
 {
     std::make_shared<SslWsUpgrader>(
         ioc,
@@ -170,6 +178,7 @@ make_websocket_session(
         etl,
         dosGuard,
         counters,
+        queue,
         std::move(buffer),
         std::move(req))
         ->run();
@@ -190,11 +199,14 @@ class Listener
     std::shared_ptr<ETLLoadBalancer> balancer_;
     std::shared_ptr<ReportingETL const> etl_;
     DOSGuard& dosGuard_;
+    WorkQueue queue_;
     RPC::Counters counters_;
 
 public:
     Listener(
         boost::asio::io_context& ioc,
+        uint32_t numWorkerThreads,
+        uint32_t maxQueueSize,
         std::optional<std::reference_wrapper<ssl::context>> ctx,
         tcp::endpoint endpoint,
         std::shared_ptr<BackendInterface const> backend,
@@ -210,6 +222,7 @@ public:
         , balancer_(balancer)
         , etl_(etl)
         , dosGuard_(dosGuard)
+        , queue_(numWorkerThreads, maxQueueSize)
     {
         boost::beast::error_code ec;
 
@@ -271,7 +284,8 @@ private:
                 balancer_,
                 etl_,
                 dosGuard_,
-                counters_)
+                counters_,
+                queue_)
                 ->run();
         }
 
@@ -306,8 +320,19 @@ make_HttpServer(
     auto const port =
         static_cast<unsigned short>(serverConfig.at("port").as_int64());
 
+    uint32_t numThreads = std::thread::hardware_concurrency();
+    if (config.contains("workers"))
+        numThreads = config.at("workers").as_int64();
+    uint32_t maxQueueSize = 0;  // no max
+    if (serverConfig.contains("max_queue_size"))
+        maxQueueSize = serverConfig.at("max_queue_size").as_int64();
+    BOOST_LOG_TRIVIAL(info) << __func__ << " Number of workers = " << numThreads
+                            << ". Max queue size = " << maxQueueSize;
+
     auto server = std::make_shared<HttpServer>(
         ioc,
+        numThreads,
+        maxQueueSize,
         sslCtx,
         boost::asio::ip::tcp::endpoint{address, port},
         backend,

src/webserver/PlainWsSession.h

@@ -38,6 +38,7 @@ public:
         std::shared_ptr<ReportingETL const> etl,
         DOSGuard& dosGuard,
         RPC::Counters& counters,
+        WorkQueue& queue,
         boost::beast::flat_buffer&& buffer)
         : WsSession(
               ioc,
@@ -47,6 +48,7 @@ public:
               etl,
               dosGuard,
               counters,
+              queue,
               std::move(buffer))
         , ws_(std::move(socket))
     {
@@ -91,6 +93,7 @@ class WsUpgrader : public std::enable_shared_from_this<WsUpgrader>
     std::shared_ptr<ReportingETL const> etl_;
     DOSGuard& dosGuard_;
     RPC::Counters& counters_;
+    WorkQueue& queue_;
     http::request<http::string_body> req_;
 
 public:
@@ -103,6 +106,7 @@ public:
         std::shared_ptr<ReportingETL const> etl,
         DOSGuard& dosGuard,
         RPC::Counters& counters,
+        WorkQueue& queue,
         boost::beast::flat_buffer&& b)
         : ioc_(ioc)
         , http_(std::move(socket))
@@ -113,6 +117,7 @@ public:
         , etl_(etl)
         , dosGuard_(dosGuard)
         , counters_(counters)
+        , queue_(queue)
     {
     }
     WsUpgrader(
@@ -124,6 +129,7 @@ public:
         std::shared_ptr<ReportingETL const> etl,
         DOSGuard& dosGuard,
         RPC::Counters& counters,
+        WorkQueue& queue,
         boost::beast::flat_buffer&& b,
         http::request<http::string_body> req)
         : ioc_(ioc)
@@ -135,6 +141,7 @@ public:
         , etl_(etl)
         , dosGuard_(dosGuard)
         , counters_(counters)
+        , queue_(queue)
         , req_(std::move(req))
     {
     }
@@ -190,6 +197,7 @@ private:
             etl_,
             dosGuard_,
             counters_,
+            queue_,
             std::move(buffer_))
             ->run(std::move(req_));
     }

src/webserver/SslHttpSession.h

@@ -26,6 +26,7 @@ public:
         std::shared_ptr<ReportingETL const> etl,
         DOSGuard& dosGuard,
         RPC::Counters& counters,
+        WorkQueue& queue,
         boost::beast::flat_buffer buffer)
         : HttpBase<SslHttpSession>(
               ioc,
@@ -35,6 +36,7 @@ public:
               etl,
               dosGuard,
               counters,
+              queue,
               std::move(buffer))
         , stream_(std::move(socket), ctx)
     {

src/webserver/SslWsSession.h

@@ -36,6 +36,7 @@ public:
         std::shared_ptr<ReportingETL const> etl,
         DOSGuard& dosGuard,
         RPC::Counters& counters,
+        WorkQueue& queue,
         boost::beast::flat_buffer&& b)
         : WsSession(
               ioc,
@@ -45,6 +46,7 @@ public:
               etl,
               dosGuard,
               counters,
+              queue,
               std::move(b))
         , ws_(std::move(stream))
     {
@@ -88,6 +90,7 @@ class SslWsUpgrader : public std::enable_shared_from_this<SslWsUpgrader>
     std::shared_ptr<ReportingETL const> etl_;
     DOSGuard& dosGuard_;
     RPC::Counters& counters_;
+    WorkQueue& queue_;
     http::request<http::string_body> req_;
 
 public:
@@ -101,6 +104,7 @@ public:
         std::shared_ptr<ReportingETL const> etl,
         DOSGuard& dosGuard,
         RPC::Counters& counters,
+        WorkQueue& queue,
         boost::beast::flat_buffer&& b)
         : ioc_(ioc)
         , https_(std::move(socket), ctx)
@@ -111,6 +115,7 @@ public:
         , etl_(etl)
         , dosGuard_(dosGuard)
         , counters_(counters)
+        , queue_(queue)
     {
     }
     SslWsUpgrader(
@@ -122,6 +127,7 @@ public:
         std::shared_ptr<ReportingETL const> etl,
         DOSGuard& dosGuard,
         RPC::Counters& counters,
+        WorkQueue& queue,
         boost::beast::flat_buffer&& b,
         http::request<http::string_body> req)
         : ioc_(ioc)
@@ -133,6 +139,7 @@ public:
         , etl_(etl)
         , dosGuard_(dosGuard)
         , counters_(counters)
+        , queue_(queue)
         , req_(std::move(req))
     {
     }
@@ -203,6 +210,7 @@ private:
             etl_,
             dosGuard_,
             counters_,
+            queue_,
             std::move(buffer_))
             ->run(std::move(req_));
     }

src/webserver/WsBase.h

@@ -9,8 +9,11 @@
 
 #include <backend/BackendInterface.h>
 #include <etl/ETLSource.h>
+#include <etl/ReportingETL.h>
 #include <rpc/Counters.h>
 #include <rpc/RPC.h>
+#include <rpc/WorkQueue.h>
+#include <subscriptions/Message.h>
 #include <subscriptions/SubscriptionManager.h>
 #include <webserver/DOSGuard.h>
 
@@ -49,7 +52,7 @@ protected:
 public:
     // Send, that enables SubscriptionManager to publish to clients
     virtual void
-    send(std::string const& msg) = 0;
+    send(std::shared_ptr<Message> msg) = 0;
 
     virtual ~WsBase()
     {
@@ -84,10 +87,11 @@ class WsSession : public WsBase,
     std::shared_ptr<ReportingETL const> etl_;
     DOSGuard& dosGuard_;
     RPC::Counters& counters_;
+    WorkQueue& queue_;
     std::mutex mtx_;
 
     bool sending_ = false;
-    std::queue<std::string> messages_;
+    std::queue<std::shared_ptr<Message>> messages_;
 
     void
     wsFail(boost::beast::error_code ec, char const* what)
@@ -98,6 +102,9 @@ class WsSession : public WsBase,
             BOOST_LOG_TRIVIAL(info)
                 << "wsFail: " << what << ": " << ec.message();
             boost::beast::get_lowest_layer(derived().ws()).socket().close(ec);
+
+            if (auto manager = subscriptions_.lock(); manager)
+                manager->cleanup(derived().shared_from_this());
         }
     }
 
@@ -110,6 +117,7 @@ public:
         std::shared_ptr<ReportingETL const> etl,
         DOSGuard& dosGuard,
         RPC::Counters& counters,
+        WorkQueue& queue,
         boost::beast::flat_buffer&& buffer)
         : buffer_(std::move(buffer))
         , ioc_(ioc)
@@ -119,6 +127,7 @@ public:
         , etl_(etl)
         , dosGuard_(dosGuard)
         , counters_(counters)
+        , queue_(queue)
     {
     }
     virtual ~WsSession()
@@ -138,7 +147,7 @@ public:
     {
         sending_ = true;
         derived().ws().async_write(
-            net::buffer(messages_.front()),
+            net::buffer(messages_.front()->data(), messages_.front()->size()),
             boost::beast::bind_front_handler(
                 &WsSession::on_write, derived().shared_from_this()));
     }
@@ -168,18 +177,25 @@ public:
     }
 
     void
-    send(std::string const& msg) override
+    send(std::shared_ptr<Message> msg) override
     {
         net::dispatch(
             derived().ws().get_executor(),
             [this,
              self = derived().shared_from_this(),
-             msg = std::string(msg)]() {
+             msg = std::move(msg)]() {
                 messages_.push(std::move(msg));
                 maybe_send_next();
             });
     }
 
+    void
+    send(std::string&& msg)
+    {
+        auto sharedMsg = std::make_shared<Message>(std::move(msg));
+        send(sharedMsg);
+    }
+
     void
     run(http::request<http::string_body> req)
     {
@@ -229,21 +245,26 @@ public:
     }
 
     void
-    handle_request(std::string const&& msg, boost::asio::yield_context& yc)
+    handle_request(
+        boost::json::object const&& request,
+        boost::json::value const& id,
+        boost::asio::yield_context& yield)
     {
         auto ip = derived().ip();
         if (!ip)
             return;
 
         boost::json::object response = {};
-        auto sendError = [this](auto error) {
-            send(boost::json::serialize(RPC::make_error(error)));
+        auto sendError = [this, &request, id](auto error) {
+            auto e = RPC::make_error(error);
+            if (!id.is_null())
+                e["id"] = id;
+            e["request"] = request;
+            this->send(boost::json::serialize(e));
         };
+
         try
         {
-            boost::json::value raw = boost::json::parse(msg);
-            boost::json::object request = raw.as_object();
-
             BOOST_LOG_TRIVIAL(debug) << " received request : " << request;
             try
             {
@@ -252,7 +273,7 @@ public:
                     return sendError(RPC::Error::rpcNOT_READY);
 
                 std::optional<RPC::Context> context = RPC::make_WsContext(
-                    yc,
+                    yield,
                     request,
                     backend_,
                     subscriptions_.lock(),
@@ -266,8 +287,6 @@ public:
                 if (!context)
                     return sendError(RPC::Error::rpcBAD_SYNTAX);
 
-                auto id = request.contains("id") ? request.at("id") : nullptr;
-
                 response = getDefaultWsResponse(id);
 
                 auto start = std::chrono::system_clock::now();
@@ -310,8 +329,23 @@ public:
             return sendError(RPC::Error::rpcINTERNAL);
         }
 
+        boost::json::array warnings;
+
+        warnings.emplace_back(RPC::make_warning(RPC::warnRPC_CLIO));
+
+        auto lastCloseAge = etl_->lastCloseAgeSeconds();
+        if (lastCloseAge >= 60)
+            warnings.emplace_back(RPC::make_warning(RPC::warnRPC_OUTDATED));
+        response["warnings"] = warnings;
         std::string responseStr = boost::json::serialize(response);
-        dosGuard_.add(*ip, responseStr.size());
+        if (!dosGuard_.add(*ip, responseStr.size()))
+        {
+            response["warning"] = "load";
+            warnings.emplace_back(RPC::make_warning(RPC::warnRPC_RATE_LIMIT));
+            response["warnings"] = warnings;
+            // reserialize if we need to include this warning
+            responseStr = boost::json::serialize(response);
+        }
         send(std::move(responseStr));
     }
 
@@ -332,25 +366,55 @@ public:
 
         BOOST_LOG_TRIVIAL(debug)
             << __func__ << " received request from ip = " << *ip;
-        if (!dosGuard_.isOk(*ip))
-        {
-            boost::json::object response;
-            response["error"] = "Too many requests. Slow down";
-            std::string responseStr = boost::json::serialize(response);
 
+        auto sendError = [this, ip](
+                             auto error,
+                             boost::json::value const& id,
+                             boost::json::object const& request) {
+            auto e = RPC::make_error(error);
+
+            if (!id.is_null())
+                e["id"] = id;
+            e["request"] = request;
+
+            auto responseStr = boost::json::serialize(e);
             BOOST_LOG_TRIVIAL(trace) << __func__ << " : " << responseStr;
-
             dosGuard_.add(*ip, responseStr.size());
             send(std::move(responseStr));
+        };
+
+        boost::json::value raw = [](std::string const&& msg) {
+            try
+            {
+                return boost::json::parse(msg);
+            }
+            catch (std::exception&)
+            {
+                return boost::json::value{nullptr};
+            }
+        }(std::move(msg));
+
+        boost::json::object request;
+        if (!raw.is_object())
+            return sendError(RPC::Error::rpcINVALID_PARAMS, nullptr, request);
+        request = raw.as_object();
+
+        auto id = request.contains("id") ? request.at("id") : nullptr;
+
+        if (!dosGuard_.isOk(*ip))
+        {
+            sendError(RPC::Error::rpcSLOW_DOWN, id, request);
         }
         else
         {
-            boost::asio::spawn(
-                derived().ws().get_executor(),
-                [m = std::move(msg), shared_this = shared_from_this()](
-                    boost::asio::yield_context yield) {
-                    shared_this->handle_request(std::move(m), yield);
-                });
+            if (!queue_.postCoro(
+                    [shared_this = shared_from_this(),
+                     r = std::move(request),
+                     id](boost::asio::yield_context yield) {
+                        shared_this->handle_request(std::move(r), id, yield);
+                    },
+                    dosGuard_.isWhiteListed(*ip)))
+                sendError(RPC::Error::rpcTOO_BUSY, id, request);
         }
 
         do_read();

test.py

@@ -475,14 +475,13 @@ async def ledger_data(ip, port, ledger, limit, binary, cursor):
     except websockets.exceptions.connectionclosederror as e:
         print(e)
 
-def writeLedgerData(data,filename):
-    print(len(data[0]))
+def writeLedgerData(state,filename):
+    print(len(state))
+
     with open(filename,'w') as f:
-        data[0].sort()
-        data[1].sort()
-        for k,v in zip(data[0],data[1]):
+        for k,v in state.items():
             f.write(k)
-            f.write('\n')
+            f.write(':')
             f.write(v)
             f.write('\n')
 
@@ -490,15 +489,14 @@ def writeLedgerData(data,filename):
 async def ledger_data_full(ip, port, ledger, binary, limit, typ=None, count=-1, marker = None):
     address = 'ws://' + str(ip) + ':' + str(port)
     try:
-        blobs = []
-        keys = []
+        state = {}
         async with websockets.connect(address,max_size=1000000000) as ws:
             if int(limit) < 2048:
                 limit = 2048
             while True:
                 res = {}
                 if marker is None:
-                    await ws.send(json.dumps({"command":"ledger_data","ledger_index":int(ledger),"binary":binary, "limit":int(limit)}))
+                    await ws.send(json.dumps({"command":"ledger_data","ledger_index":int(ledger),"binary":binary, "limit":int(limit),"out_of_order":True}))
                     res = json.loads(await ws.recv())
                     
                 else:
@@ -520,16 +518,15 @@ async def ledger_data_full(ip, port, ledger, binary, limit, typ=None, count=-1,
                     if binary:
                         if typ is None or x["data"][2:6] == typ:
                             #print(json.dumps(x))
-                            keys.append(x["index"])
+                            state[x["index"]] = x["data"]
                     else:
                         if typ is None or x["LedgerEntryType"] == typ:
-                            blobs.append(x)
-                            keys.append(x["index"])
-                if count != -1 and len(keys) > count:
+                            state[x["index"]] = x
+                if count != -1 and len(state) > count:
                     print("stopping early")
-                    print(len(keys))
+                    print(len(state))
                     print("done")
-                    return (keys,blobs)
+                    return state
                 if "cursor" in res:
                     marker = res["cursor"]
                     print(marker)
@@ -538,7 +535,7 @@ async def ledger_data_full(ip, port, ledger, binary, limit, typ=None, count=-1,
                     print(marker)
                 else:
                     print("done")
-                    return (keys, blobs)
+                    return state
 
 
     except websockets.exceptions.connectionclosederror as e:
@@ -574,7 +571,19 @@ def compare_book_offers(aldous, p2p):
     print("offers match!")
     return True
                     
-        
+async def book_changes(ip, port, ledger):
+    address = 'ws://' + str(ip) + ':' + str(port)
+    try:
+        async with websockets.connect(address) as ws:
+            await ws.send(json.dumps({
+                "command" : "book_changes",
+                "ledger_index" : ledger
+            }))
+            res = json.loads(await ws.recv())
+            print(json.dumps(res, indent=4, sort_keys=True))
+    except websockets.exceptions.connectionclosederror as e:
+        print(e)
+
 async def book_offerses(ip, port, ledger, books, numCalls):
     address = 'ws://' + str(ip) + ':' + str(port)
     random.seed()
@@ -792,6 +801,7 @@ async def fee(ip, port):
             print(json.dumps(res,indent=4,sort_keys=True))
     except websockets.exceptions.connectionclosederror as e:
         print(e)
+
 async def server_info(ip, port):
     address = 'ws://' + str(ip) + ':' + str(port)
     try:
@@ -971,7 +981,7 @@ async def verifySubscribe(ip,clioPort,ripdPort):
     
 
 parser = argparse.ArgumentParser(description='test script for xrpl-reporting')
-parser.add_argument('action', choices=["account_info", "tx", "txs","account_tx", "account_tx_full","ledger_data", "ledger_data_full", "book_offers","ledger","ledger_range","ledger_entry", "ledgers", "ledger_entries","account_txs","account_infos","account_txs_full","book_offerses","ledger_diff","perf","fee","server_info", "gaps","subscribe","verify_subscribe","call"])
+parser.add_argument('action', choices=["account_info", "tx", "txs","account_tx", "account_tx_full","ledger_data", "ledger_data_full", "book_offers","ledger","ledger_range","ledger_entry", "ledgers", "ledger_entries","account_txs","account_infos","account_txs_full","book_changes","book_offerses","ledger_diff","perf","fee","server_info", "gaps","subscribe","verify_subscribe","call"])
 
 parser.add_argument('--ip', default='127.0.0.1')
 parser.add_argument('--port', default='8080')
@@ -1159,14 +1169,17 @@ def run(args):
         end = datetime.datetime.now().timestamp()
         num = int(args.numRunners) * int(args.numCalls)
         print("Completed " + str(num) + " in " + str(end - start) + " seconds. Throughput = " + str(num / (end - start)) + " calls per second")
-    
+   
+    elif args.action == "book_changes":
+        asyncio.get_event_loop().run_until_complete(book_changes(args.ip, args.port, int(args.ledger)))
+            
     elif args.action == "book_offerses":
         books = getBooks(args.filename)
         async def runner():
 
             tasks = []
-            for x in range(0,int(args.numRunners)):
-                tasks.append(asyncio.create_task(book_offerses(args.ip, args.port,int(args.ledger),books, int(args.numCalls))))
+            for x in range(0, int(args.numRunners)):
+                tasks.append(asyncio.create_task(book_offerses(args.ip, args.port, int(args.ledger), books, int(args.numCalls))))
             for t in tasks:
                 await t
 
@@ -1263,7 +1276,7 @@ def run(args):
 
         res = asyncio.get_event_loop().run_until_complete(
                 ledger_data_full(args.ip, args.port, args.ledger, bool(args.binary), args.limit,args.type, int(args.count), args.marker))
-        print(len(res[0]))
+        print(len(res))
         if args.verify:
             writeLedgerData(res,args.filename)
 

unittests/main.cpp

@@ -1,5 +1,6 @@
 #include <algorithm>
 #include <backend/DBHelpers.h>
+#include <etl/ReportingETL.h>
 #include <gtest/gtest.h>
 #include <rpc/RPCHelpers.h>
 
@@ -296,6 +297,122 @@ TEST(BackendTest, Basic)
                     "E0311EB450B6177F969B94DBDDA83E99B7A0576ACD9079573876F16C0C"
                     "004F06";
 
+                // An NFTokenMint tx
+                std::string nftTxnHex =
+                    "1200192200000008240011CC9B201B001F71D6202A0000000168400000"
+                    "000000000C7321ED475D1452031E8F9641AF1631519A58F7B8681E172E"
+                    "4838AA0E59408ADA1727DD74406960041F34F10E0CBB39444B4D4E577F"
+                    "C0B7E8D843D091C2917E96E7EE0E08B30C91413EC551A2B8A1D405E8BA"
+                    "34FE185D8B10C53B40928611F2DE3B746F0303751868747470733A2F2F"
+                    "677265677765697362726F642E636F6D81146203F49C21D5D6E022CB16"
+                    "DE3538F248662FC73C";
+
+                std::string nftTxnMeta =
+                    "201C00000001F8E511005025001F71B3556ED9C9459001E4F4A9121F4E"
+                    "07AB6D14898A5BBEF13D85C25D743540DB59F3CF566203F49C21D5D6E0"
+                    "22CB16DE3538F248662FC73CFFFFFFFFFFFFFFFFFFFFFFFFE6FAEC5A00"
+                    "0800006203F49C21D5D6E022CB16DE3538F248662FC73C8962EFA00000"
+                    "0006751868747470733A2F2F677265677765697362726F642E636F6DE1"
+                    "EC5A000800006203F49C21D5D6E022CB16DE3538F248662FC73C93E8B1"
+                    "C200000028751868747470733A2F2F677265677765697362726F642E63"
+                    "6F6DE1EC5A000800006203F49C21D5D6E022CB16DE3538F248662FC73C"
+                    "9808B6B90000001D751868747470733A2F2F677265677765697362726F"
+                    "642E636F6DE1EC5A000800006203F49C21D5D6E022CB16DE3538F24866"
+                    "2FC73C9C28BBAC00000012751868747470733A2F2F6772656777656973"
+                    "62726F642E636F6DE1EC5A000800006203F49C21D5D6E022CB16DE3538"
+                    "F248662FC73CA048C0A300000007751868747470733A2F2F6772656777"
+                    "65697362726F642E636F6DE1EC5A000800006203F49C21D5D6E022CB16"
+                    "DE3538F248662FC73CAACE82C500000029751868747470733A2F2F6772"
+                    "65677765697362726F642E636F6DE1EC5A000800006203F49C21D5D6E0"
+                    "22CB16DE3538F248662FC73CAEEE87B80000001E751868747470733A2F"
+                    "2F677265677765697362726F642E636F6DE1EC5A000800006203F49C21"
+                    "D5D6E022CB16DE3538F248662FC73CB30E8CAF00000013751868747470"
+                    "733A2F2F677265677765697362726F642E636F6DE1EC5A000800006203"
+                    "F49C21D5D6E022CB16DE3538F248662FC73CB72E91A200000008751868"
+                    "747470733A2F2F677265677765697362726F642E636F6DE1EC5A000800"
+                    "006203F49C21D5D6E022CB16DE3538F248662FC73CC1B453C40000002A"
+                    "751868747470733A2F2F677265677765697362726F642E636F6DE1EC5A"
+                    "000800006203F49C21D5D6E022CB16DE3538F248662FC73CC5D458BB00"
+                    "00001F751868747470733A2F2F677265677765697362726F642E636F6D"
+                    "E1EC5A000800006203F49C21D5D6E022CB16DE3538F248662FC73CC9F4"
+                    "5DAE00000014751868747470733A2F2F677265677765697362726F642E"
+                    "636F6DE1EC5A000800006203F49C21D5D6E022CB16DE3538F248662FC7"
+                    "3CCE1462A500000009751868747470733A2F2F67726567776569736272"
+                    "6F642E636F6DE1EC5A000800006203F49C21D5D6E022CB16DE3538F248"
+                    "662FC73CD89A24C70000002B751868747470733A2F2F67726567776569"
+                    "7362726F642E636F6DE1EC5A000800006203F49C21D5D6E022CB16DE35"
+                    "38F248662FC73CDCBA29BA00000020751868747470733A2F2F67726567"
+                    "7765697362726F642E636F6DE1EC5A000800006203F49C21D5D6E022CB"
+                    "16DE3538F248662FC73CE0DA2EB100000015751868747470733A2F2F67"
+                    "7265677765697362726F642E636F6DE1EC5A000800006203F49C21D5D6"
+                    "E022CB16DE3538F248662FC73CE4FA33A40000000A751868747470733A"
+                    "2F2F677265677765697362726F642E636F6DE1EC5A000800006203F49C"
+                    "21D5D6E022CB16DE3538F248662FC73CF39FFABD000000217518687474"
+                    "70733A2F2F677265677765697362726F642E636F6DE1EC5A0008000062"
+                    "03F49C21D5D6E022CB16DE3538F248662FC73CF7BFFFB0000000167518"
+                    "68747470733A2F2F677265677765697362726F642E636F6DE1EC5A0008"
+                    "00006203F49C21D5D6E022CB16DE3538F248662FC73CFBE004A7000000"
+                    "0B751868747470733A2F2F677265677765697362726F642E636F6DE1F1"
+                    "E1E72200000000501A6203F49C21D5D6E022CB16DE3538F248662FC73C"
+                    "662FC73C8962EFA000000006FAEC5A000800006203F49C21D5D6E022CB"
+                    "16DE3538F248662FC73C8962EFA000000006751868747470733A2F2F67"
+                    "7265677765697362726F642E636F6DE1EC5A000800006203F49C21D5D6"
+                    "E022CB16DE3538F248662FC73C93E8B1C200000028751868747470733A"
+                    "2F2F677265677765697362726F642E636F6DE1EC5A000800006203F49C"
+                    "21D5D6E022CB16DE3538F248662FC73C9808B6B90000001D7518687474"
+                    "70733A2F2F677265677765697362726F642E636F6DE1EC5A0008000062"
+                    "03F49C21D5D6E022CB16DE3538F248662FC73C9C28BBAC000000127518"
+                    "68747470733A2F2F677265677765697362726F642E636F6DE1EC5A0008"
+                    "00006203F49C21D5D6E022CB16DE3538F248662FC73CA048C0A3000000"
+                    "07751868747470733A2F2F677265677765697362726F642E636F6DE1EC"
+                    "5A000800006203F49C21D5D6E022CB16DE3538F248662FC73CAACE82C5"
+                    "00000029751868747470733A2F2F677265677765697362726F642E636F"
+                    "6DE1EC5A000800006203F49C21D5D6E022CB16DE3538F248662FC73CAE"
+                    "EE87B80000001E751868747470733A2F2F677265677765697362726F64"
+                    "2E636F6DE1EC5A000800006203F49C21D5D6E022CB16DE3538F248662F"
+                    "C73CB30E8CAF00000013751868747470733A2F2F677265677765697362"
+                    "726F642E636F6DE1EC5A000800006203F49C21D5D6E022CB16DE3538F2"
+                    "48662FC73CB72E91A200000008751868747470733A2F2F677265677765"
+                    "697362726F642E636F6DE1EC5A000800006203F49C21D5D6E022CB16DE"
+                    "3538F248662FC73CC1B453C40000002A751868747470733A2F2F677265"
+                    "677765697362726F642E636F6DE1EC5A000800006203F49C21D5D6E022"
+                    "CB16DE3538F248662FC73CC5D458BB0000001F751868747470733A2F2F"
+                    "677265677765697362726F642E636F6DE1EC5A000800006203F49C21D5"
+                    "D6E022CB16DE3538F248662FC73CC9F45DAE0000001475186874747073"
+                    "3A2F2F677265677765697362726F642E636F6DE1EC5A000800006203F4"
+                    "9C21D5D6E022CB16DE3538F248662FC73CCE1462A50000000975186874"
+                    "7470733A2F2F677265677765697362726F642E636F6DE1EC5A00080000"
+                    "6203F49C21D5D6E022CB16DE3538F248662FC73CD89A24C70000002B75"
+                    "1868747470733A2F2F677265677765697362726F642E636F6DE1EC5A00"
+                    "0800006203F49C21D5D6E022CB16DE3538F248662FC73CDCBA29BA0000"
+                    "0020751868747470733A2F2F677265677765697362726F642E636F6DE1"
+                    "EC5A000800006203F49C21D5D6E022CB16DE3538F248662FC73CE0DA2E"
+                    "B100000015751868747470733A2F2F677265677765697362726F642E63"
+                    "6F6DE1EC5A000800006203F49C21D5D6E022CB16DE3538F248662FC73C"
+                    "E4FA33A40000000A751868747470733A2F2F677265677765697362726F"
+                    "642E636F6DE1EC5A000800006203F49C21D5D6E022CB16DE3538F24866"
+                    "2FC73CEF7FF5C60000002C751868747470733A2F2F6772656777656973"
+                    "62726F642E636F6DE1EC5A000800006203F49C21D5D6E022CB16DE3538"
+                    "F248662FC73CF39FFABD00000021751868747470733A2F2F6772656777"
+                    "65697362726F642E636F6DE1EC5A000800006203F49C21D5D6E022CB16"
+                    "DE3538F248662FC73CF7BFFFB000000016751868747470733A2F2F6772"
+                    "65677765697362726F642E636F6DE1EC5A000800006203F49C21D5D6E0"
+                    "22CB16DE3538F248662FC73CFBE004A70000000B751868747470733A2F"
+                    "2F677265677765697362726F642E636F6DE1F1E1E1E511006125001F71"
+                    "B3556ED9C9459001E4F4A9121F4E07AB6D14898A5BBEF13D85C25D7435"
+                    "40DB59F3CF56BE121B82D5812149D633F605EB07265A80B762A365CE94"
+                    "883089FEEE4B955701E6240011CC9B202B0000002C6240000002540BE3"
+                    "ECE1E72200000000240011CC9C2D0000000A202B0000002D202C000000"
+                    "066240000002540BE3E081146203F49C21D5D6E022CB16DE3538F24866"
+                    "2FC73CE1E1F1031000";
+                std::string nftTxnHashHex =
+                    "6C7F69A6D25A13AC4A2E9145999F45D4674F939900017A96885FDC2757"
+                    "E9284E";
+                ripple::uint256 nftID;
+                EXPECT_TRUE(
+                    nftID.parseHex("000800006203F49C21D5D6E022CB16DE3538F248662"
+                                   "FC73CEF7FF5C60000002C"));
+
                 std::string metaBlob = hexStringToBinaryString(metaHex);
                 std::string txnBlob = hexStringToBinaryString(txnHex);
                 std::string hashBlob = hexStringToBinaryString(hashHex);
@@ -304,6 +421,10 @@ TEST(BackendTest, Basic)
                     hexStringToBinaryString(accountIndexHex);
                 std::vector<ripple::AccountID> affectedAccounts;
 
+                std::string nftTxnBlob = hexStringToBinaryString(nftTxnHex);
+                std::string nftTxnMetaBlob =
+                    hexStringToBinaryString(nftTxnMeta);
+
                 {
                     backend->startWrites();
                     lgrInfoNext.seq = lgrInfoNext.seq + 1;
@@ -322,23 +443,62 @@ TEST(BackendTest, Basic)
                     {
                         affectedAccounts.push_back(a);
                     }
-
                     std::vector<AccountTransactionsData> accountTxData;
                     accountTxData.emplace_back(txMeta, hash256, journal);
+
+                    ripple::uint256 nftHash256;
+                    EXPECT_TRUE(nftHash256.parseHex(nftTxnHashHex));
+                    ripple::TxMeta nftTxMeta{
+                        nftHash256, lgrInfoNext.seq, nftTxnMetaBlob};
+                    ripple::SerialIter it{nftTxnBlob.data(), nftTxnBlob.size()};
+                    ripple::STTx sttx{it};
+                    auto const [parsedNFTTxsRef, parsedNFT] =
+                        getNFTData(nftTxMeta, sttx);
+                    // need to copy the nft txns so we can std::move later
+                    std::vector<NFTTransactionsData> parsedNFTTxs;
+                    parsedNFTTxs.insert(
+                        parsedNFTTxs.end(),
+                        parsedNFTTxsRef.begin(),
+                        parsedNFTTxsRef.end());
+                    EXPECT_EQ(parsedNFTTxs.size(), 1);
+                    EXPECT_TRUE(parsedNFT.has_value());
+                    EXPECT_EQ(parsedNFT->tokenID, nftID);
+                    std::vector<NFTsData> nftData;
+                    nftData.push_back(*parsedNFT);
+
                     backend->writeLedger(
-                        lgrInfoNext,
-                        std::move(ledgerInfoToBinaryString(lgrInfoNext)));
+                        lgrInfoNext, ledgerInfoToBinaryString(lgrInfoNext));
                     backend->writeTransaction(
-                        std::move(std::string{hashBlob}),
+                        std::string{hashBlob},
                         lgrInfoNext.seq,
                         lgrInfoNext.closeTime.time_since_epoch().count(),
-                        std::move(std::string{txnBlob}),
-                        std::move(std::string{metaBlob}));
+                        std::string{txnBlob},
+                        std::string{metaBlob});
                     backend->writeAccountTransactions(std::move(accountTxData));
+
+                    // NFT writing not yet implemented for pg
+                    if (config == cassandraConfig)
+                    {
+                        backend->writeNFTs(std::move(nftData));
+                        backend->writeNFTTransactions(std::move(parsedNFTTxs));
+                    }
+                    else
+                    {
+                        EXPECT_THROW(
+                            { backend->writeNFTs(std::move(nftData)); },
+                            std::runtime_error);
+                        EXPECT_THROW(
+                            {
+                                backend->writeNFTTransactions(
+                                    std::move(parsedNFTTxs));
+                            },
+                            std::runtime_error);
+                    }
+
                     backend->writeLedgerObject(
-                        std::move(std::string{accountIndexBlob}),
+                        std::string{accountIndexBlob},
                         lgrInfoNext.seq,
-                        std::move(std::string{accountBlob}));
+                        std::string{accountBlob});
                     backend->writeSuccessor(
                         uint256ToString(Backend::firstKey),
                         lgrInfoNext.seq,
@@ -384,6 +544,34 @@ TEST(BackendTest, Basic)
                         EXPECT_FALSE(cursor);
                     }
 
+                    // NFT fetching not yet implemented for pg
+                    if (config == cassandraConfig)
+                    {
+                        auto nft =
+                            backend->fetchNFT(nftID, lgrInfoNext.seq, yield);
+                        EXPECT_TRUE(nft.has_value());
+                        auto [nftTxns, cursor] = backend->fetchNFTTransactions(
+                            nftID, 100, true, {}, yield);
+                        EXPECT_EQ(nftTxns.size(), 1);
+                        EXPECT_EQ(nftTxns[0], nftTxns[0]);
+                        EXPECT_FALSE(cursor);
+                    }
+                    else
+                    {
+                        EXPECT_THROW(
+                            {
+                                backend->fetchNFT(
+                                    nftID, lgrInfoNext.seq, yield);
+                            },
+                            std::runtime_error);
+                        EXPECT_THROW(
+                            {
+                                backend->fetchNFTTransactions(
+                                    nftID, 100, true, {}, yield);
+                            },
+                            std::runtime_error);
+                    }
+
                     ripple::uint256 key256;
                     EXPECT_TRUE(key256.parseHex(accountIndexHex));
                     auto obj = backend->fetchLedgerObject(
@@ -417,16 +605,15 @@ TEST(BackendTest, Basic)
                         ~(lgrInfoNext.accountHash ^ lgrInfoNext.txHash);
 
                     backend->writeLedger(
-                        lgrInfoNext,
-                        std::move(ledgerInfoToBinaryString(lgrInfoNext)));
+                        lgrInfoNext, ledgerInfoToBinaryString(lgrInfoNext));
                     std::shuffle(
                         accountBlob.begin(),
                         accountBlob.end(),
                         std::default_random_engine(seed));
                     backend->writeLedgerObject(
-                        std::move(std::string{accountIndexBlob}),
+                        std::string{accountIndexBlob},
                         lgrInfoNext.seq,
-                        std::move(std::string{accountBlob}));
+                        std::string{accountBlob});
 
                     ASSERT_TRUE(backend->finishWrites(lgrInfoNext.seq));
                 }
@@ -480,12 +667,11 @@ TEST(BackendTest, Basic)
                         ~(lgrInfoNext.accountHash ^ lgrInfoNext.txHash);
 
                     backend->writeLedger(
-                        lgrInfoNext,
-                        std::move(ledgerInfoToBinaryString(lgrInfoNext)));
+                        lgrInfoNext, ledgerInfoToBinaryString(lgrInfoNext));
                     backend->writeLedgerObject(
-                        std::move(std::string{accountIndexBlob}),
+                        std::string{accountIndexBlob},
                         lgrInfoNext.seq,
-                        std::move(std::string{}));
+                        std::string{});
                     backend->writeSuccessor(
                         uint256ToString(Backend::firstKey),
                         lgrInfoNext.seq,
@@ -527,9 +713,8 @@ TEST(BackendTest, Basic)
                     EXPECT_FALSE(obj);
                 }
 
-                auto generateObjects = [seed](
-                                           size_t numObjects,
-                                           uint32_t ledgerSequence) {
+                auto generateObjects = [](size_t numObjects,
+                                          uint32_t ledgerSequence) {
                     std::vector<std::pair<std::string, std::string>> res{
                         numObjects};
                     ripple::uint256 key;
@@ -551,26 +736,26 @@ TEST(BackendTest, Basic)
                     }
                     return objs;
                 };
-                auto generateTxns =
-                    [seed](size_t numTxns, uint32_t ledgerSequence) {
-                        std::vector<
-                            std::tuple<std::string, std::string, std::string>>
-                            res{numTxns};
-                        ripple::uint256 base;
-                        base = ledgerSequence * 100000;
-                        for (auto& blob : res)
-                        {
-                            ++base;
-                            std::string hashStr{
-                                (const char*)base.data(), base.size()};
-                            std::string txnStr =
-                                "tx" + std::to_string(ledgerSequence) + hashStr;
-                            std::string metaStr = "meta" +
-                                std::to_string(ledgerSequence) + hashStr;
-                            blob = std::make_tuple(hashStr, txnStr, metaStr);
-                        }
-                        return res;
-                    };
+                auto generateTxns = [](size_t numTxns,
+                                       uint32_t ledgerSequence) {
+                    std::vector<
+                        std::tuple<std::string, std::string, std::string>>
+                        res{numTxns};
+                    ripple::uint256 base;
+                    base = ledgerSequence * 100000;
+                    for (auto& blob : res)
+                    {
+                        ++base;
+                        std::string hashStr{
+                            (const char*)base.data(), base.size()};
+                        std::string txnStr =
+                            "tx" + std::to_string(ledgerSequence) + hashStr;
+                        std::string metaStr =
+                            "meta" + std::to_string(ledgerSequence) + hashStr;
+                        blob = std::make_tuple(hashStr, txnStr, metaStr);
+                    }
+                    return res;
+                };
                 auto generateAccounts = [](uint32_t ledgerSequence,
                                            uint32_t numAccounts) {
                     std::vector<ripple::AccountID> accounts;
@@ -635,7 +820,7 @@ TEST(BackendTest, Basic)
                     backend->startWrites();
 
                     backend->writeLedger(
-                        lgrInfo, std::move(ledgerInfoToBinaryString(lgrInfo)));
+                        lgrInfo, ledgerInfoToBinaryString(lgrInfo));
                     for (auto [hash, txn, meta] : txns)
                     {
                         backend->writeTransaction(
@@ -729,8 +914,7 @@ TEST(BackendTest, Basic)
                     for (auto [account, data] : accountTx)
                     {
                         std::vector<Backend::TransactionAndMetadata> retData;
-                        std::optional<Backend::AccountTransactionsCursor>
-                            cursor;
+                        std::optional<Backend::TransactionsCursor> cursor;
                         do
                         {
                             uint32_t limit = 10;
@@ -1854,12 +2038,11 @@ TEST(Backend, cacheIntegration)
                     lgrInfoNext.hash++;
 
                     backend->writeLedger(
-                        lgrInfoNext,
-                        std::move(ledgerInfoToBinaryString(lgrInfoNext)));
+                        lgrInfoNext, ledgerInfoToBinaryString(lgrInfoNext));
                     backend->writeLedgerObject(
-                        std::move(std::string{accountIndexBlob}),
+                        std::string{accountIndexBlob},
                         lgrInfoNext.seq,
-                        std::move(std::string{accountBlob}));
+                        std::string{accountBlob});
                     auto key =
                         ripple::uint256::fromVoidChecked(accountIndexBlob);
                     backend->cache().update(
@@ -1921,8 +2104,7 @@ TEST(Backend, cacheIntegration)
                         ~(lgrInfoNext.accountHash ^ lgrInfoNext.txHash);
 
                     backend->writeLedger(
-                        lgrInfoNext,
-                        std::move(ledgerInfoToBinaryString(lgrInfoNext)));
+                        lgrInfoNext, ledgerInfoToBinaryString(lgrInfoNext));
                     std::shuffle(
                         accountBlob.begin(),
                         accountBlob.end(),
@@ -1933,9 +2115,9 @@ TEST(Backend, cacheIntegration)
                         {{*key, {accountBlob.begin(), accountBlob.end()}}},
                         lgrInfoNext.seq);
                     backend->writeLedgerObject(
-                        std::move(std::string{accountIndexBlob}),
+                        std::string{accountIndexBlob},
                         lgrInfoNext.seq,
-                        std::move(std::string{accountBlob}));
+                        std::string{accountBlob});
 
                     ASSERT_TRUE(backend->finishWrites(lgrInfoNext.seq));
                 }
@@ -1983,15 +2165,14 @@ TEST(Backend, cacheIntegration)
                         ~(lgrInfoNext.accountHash ^ lgrInfoNext.txHash);
 
                     backend->writeLedger(
-                        lgrInfoNext,
-                        std::move(ledgerInfoToBinaryString(lgrInfoNext)));
+                        lgrInfoNext, ledgerInfoToBinaryString(lgrInfoNext));
                     auto key =
                         ripple::uint256::fromVoidChecked(accountIndexBlob);
                     backend->cache().update({{*key, {}}}, lgrInfoNext.seq);
                     backend->writeLedgerObject(
-                        std::move(std::string{accountIndexBlob}),
+                        std::string{accountIndexBlob},
                         lgrInfoNext.seq,
-                        std::move(std::string{}));
+                        std::string{});
                     backend->writeSuccessor(
                         uint256ToString(Backend::firstKey),
                         lgrInfoNext.seq,
@@ -2027,9 +2208,8 @@ TEST(Backend, cacheIntegration)
                     EXPECT_FALSE(obj);
                 }
 
-                auto generateObjects = [seed](
-                                           size_t numObjects,
-                                           uint32_t ledgerSequence) {
+                auto generateObjects = [](size_t numObjects,
+                                          uint32_t ledgerSequence) {
                     std::vector<std::pair<std::string, std::string>> res{
                         numObjects};
                     ripple::uint256 key;