feat: Choose writer by cluster communication (#2830)

Fixes #1974

src/cluster/Backend.cpp

@@ -0,0 +1,141 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2025, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include "cluster/Backend.hpp"
+
+#include "cluster/ClioNode.hpp"
+#include "data/BackendInterface.hpp"
+#include "etl/WriterState.hpp"
+
+#include <boost/asio/bind_cancellation_slot.hpp>
+#include <boost/asio/cancellation_type.hpp>
+#include <boost/asio/error.hpp>
+#include <boost/asio/execution_context.hpp>
+#include <boost/asio/executor.hpp>
+#include <boost/asio/spawn.hpp>
+#include <boost/asio/steady_timer.hpp>
+#include <boost/asio/thread_pool.hpp>
+#include <boost/asio/use_future.hpp>
+#include <boost/json/parse.hpp>
+#include <boost/json/serialize.hpp>
+#include <boost/json/value.hpp>
+#include <boost/json/value_from.hpp>
+#include <boost/json/value_to.hpp>
+#include <boost/uuid/random_generator.hpp>
+#include <boost/uuid/uuid.hpp>
+#include <fmt/format.h>
+
+#include <chrono>
+#include <memory>
+#include <utility>
+#include <vector>
+
+namespace cluster {
+
+Backend::Backend(
+    boost::asio::thread_pool& ctx,
+    std::shared_ptr<data::BackendInterface> backend,
+    std::unique_ptr<etl::WriterStateInterface const> writerState,
+    std::chrono::steady_clock::duration readInterval,
+    std::chrono::steady_clock::duration writeInterval
+)
+    : backend_(std::move(backend))
+    , writerState_(std::move(writerState))
+    , readerTask_(readInterval, ctx)
+    , writerTask_(writeInterval, ctx)
+    , selfUuid_(std::make_shared<boost::uuids::uuid>(boost::uuids::random_generator{}()))
+{
+}
+
+void
+Backend::run()
+{
+    readerTask_.run([this](boost::asio::yield_context yield) {
+        auto clusterData = doRead(yield);
+        onNewState_(selfUuid_, std::make_shared<ClusterData>(std::move(clusterData)));
+    });
+
+    writerTask_.run([this]() { doWrite(); });
+}
+
+Backend::~Backend()
+{
+    stop();
+}
+
+void
+Backend::stop()
+{
+    readerTask_.stop();
+    writerTask_.stop();
+}
+
+ClioNode::CUuid
+Backend::selfId() const
+{
+    return selfUuid_;
+}
+
+Backend::ClusterData
+Backend::doRead(boost::asio::yield_context yield)
+{
+    BackendInterface::ClioNodesDataFetchResult expectedResult;
+    try {
+        expectedResult = backend_->fetchClioNodesData(yield);
+    } catch (...) {
+        expectedResult = std::unexpected{"Failed to fetch Clio nodes data"};
+    }
+
+    if (!expectedResult.has_value()) {
+        return std::unexpected{std::move(expectedResult).error()};
+    }
+
+    std::vector<ClioNode> otherNodesData;
+    for (auto const& [uuid, nodeDataStr] : expectedResult.value()) {
+        if (uuid == *selfUuid_) {
+            continue;
+        }
+
+        boost::system::error_code errorCode;
+        auto const json = boost::json::parse(nodeDataStr, errorCode);
+        if (errorCode.failed()) {
+            return std::unexpected{fmt::format("Error parsing json from DB: {}", nodeDataStr)};
+        }
+
+        auto expectedNodeData = boost::json::try_value_to<ClioNode>(json);
+        if (expectedNodeData.has_error()) {
+            return std::unexpected{fmt::format("Error converting json to ClioNode: {}", nodeDataStr)};
+        }
+        *expectedNodeData->uuid = uuid;
+        otherNodesData.push_back(std::move(expectedNodeData).value());
+    }
+    otherNodesData.push_back(ClioNode::from(selfUuid_, *writerState_));
+    return otherNodesData;
+}
+
+void
+Backend::doWrite()
+{
+    auto const selfData = ClioNode::from(selfUuid_, *writerState_);
+    boost::json::value jsonValue{};
+    boost::json::value_from(selfData, jsonValue);
+    backend_->writeNodeMessage(*selfData.uuid, boost::json::serialize(jsonValue.as_object()));
+}
+
+}  // namespace cluster