From b45b34edb132d59c44f0c75e3baba40be2b49757 Mon Sep 17 00:00:00 2001
From: ethanlabelle <37966268+ethanlabelle@users.noreply.github.com>
Date: Tue, 14 Jun 2022 14:50:42 -0400
Subject: [PATCH] append warning to response if clio is out of date (#175)

Fixes #46.
---
 src/etl/ReportingETL.h   | 33 +++++++++++++++++++--------------
 src/webserver/HttpBase.h | 20 ++++++++++++++++++--
 src/webserver/WsBase.h   | 23 ++++++++++++++++++++++-
 3 files changed, 59 insertions(+), 17 deletions(-)

diff --git a/src/etl/ReportingETL.h b/src/etl/ReportingETL.h
index 9ab108f70..3c68d35d0 100644
--- a/src/etl/ReportingETL.h
+++ b/src/etl/ReportingETL.h
@@ -130,19 +130,12 @@ private:
     /// 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();
     }
 
@@ -322,13 +315,25 @@ 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();
+    }
 };
 
 #endif
diff --git a/src/webserver/HttpBase.h b/src/webserver/HttpBase.h
index da05563c5..0b16f12b5 100644
--- a/src/webserver/HttpBase.h
+++ b/src/webserver/HttpBase.h
@@ -405,9 +405,25 @@ handle_request(
             responseStr = boost::json::serialize(response);
         }
 
+        auto warningFlag = false;
+        boost::json::array warnings;
         if (!dosGuard.add(ip, responseStr.size()))
-            result["warning"] = "Too many requests";
-
+        {
+            warnings.emplace_back("Too many requests");
+            warningFlag = true;
+        }
+        auto lastPublishAge = context->etl->lastPublishAgeSeconds();
+        if (lastPublishAge >= 60)
+        {
+            warnings.emplace_back("This server may be out of date");
+            warningFlag = true;
+        }
+        // reserialize only if a warning was appended.
+        if (warningFlag)
+        {
+            result["warning"] = warnings;
+            responseStr = boost::json::serialize(response);
+        }
         return send(
             httpResponse(http::status::ok, "application/json", responseStr));
     }
diff --git a/src/webserver/WsBase.h b/src/webserver/WsBase.h
index 9a6bbc6ac..2d4d313fd 100644
--- a/src/webserver/WsBase.h
+++ b/src/webserver/WsBase.h
@@ -9,6 +9,7 @@
 
 #include <backend/BackendInterface.h>
 #include <etl/ETLSource.h>
+#include <etl/ReportingETL.h>
 #include <rpc/Counters.h>
 #include <rpc/RPC.h>
 #include <subscriptions/Message.h>
@@ -322,7 +323,27 @@ public:
         }
 
         std::string responseStr = boost::json::serialize(response);
-        dosGuard_.add(*ip, responseStr.size());
+        boost::json::array warnings;
+        auto warningFlag = false;
+
+        if (!dosGuard_.add(*ip, responseStr.size()))
+        {
+            warnings.emplace_back("Too many requests");
+            warningFlag = true;
+        }
+        auto lastPublishAge = etl_->lastPublishAgeSeconds();
+        if (lastPublishAge >= 60)
+        {
+            warnings.emplace_back("This server may be out of date");
+            warningFlag = true;
+        }
+        // reserialize if a warning was appended
+        if (warningFlag)
+        {
+            auto& result = response["result"].as_object();
+            result["warning"] = warnings;
+            responseStr = boost::json::serialize(response);
+        }
         send(std::move(responseStr));
     }