JsonRpcConnection: Log message processing stats

lib/remote/jsonrpcconnection.cpp

@@ -60,6 +60,8 @@ void JsonRpcConnection::Start()
 
 void JsonRpcConnection::HandleIncomingMessages(boost::asio::yield_context yc)
 {
+	namespace  ch = std::chrono;
+
 	m_Stream->next_layer().SetSeen(&m_Seen);
 
 	for (;;) {
@@ -78,9 +80,37 @@ void JsonRpcConnection::HandleIncomingMessages(boost::asio::yield_context yc)
 		m_Seen = Utility::GetTime();
 
 		try {
+			auto start (ch::steady_clock::now());
+			ch::steady_clock::duration cpuBoundDuration;
+
+			String rpcMethod;
+
+			Defer addLogStats ([this, &rpcMethod,  &start, &cpuBoundDuration]() {
+				auto severity = LogDebug;
+
+				auto duration = ch::steady_clock::now() - start;
+				if (duration >= ch::seconds(5)) {
+					// Processing that RPC message seems to take an unexpectedly long time,
+					// so promote the log entry from debug to warning.
+					severity = LogWarning;
+				}
+
+				Log statsLog(severity, "JsonRpcConnection");
+				statsLog << "Processing JSON-RPC '" << rpcMethod << "' message for identity '" << m_Identity << "'";
+
+				if (cpuBoundDuration >= ch::seconds(1)) {
+					statsLog << " waited '" << ch::duration_cast<ch::milliseconds>(cpuBoundDuration).count() << "ms' on semaphore and";
+				}
+
+				statsLog << " took total " << ch::duration_cast<ch::milliseconds>(duration).count() << "ms.";
+			});
+
 			CpuBoundWork handleMessage (yc);
 
-			MessageHandler(message);
+			// Cache the elapsed time to acquire a CPU semaphore used to detect extremely heavy workloads.
+			cpuBoundDuration = ch::steady_clock::now() - start;
+
+			MessageHandler(message, rpcMethod);
 
 			l_TaskStats.InsertValue(Utility::GetTime(), 1);
 		} catch (const std::exception& ex) {
@@ -245,9 +275,13 @@ void JsonRpcConnection::Disconnect()
 	});
 }
 
-void JsonRpcConnection::MessageHandler(const String& jsonString)
+void JsonRpcConnection::MessageHandler(const String& jsonString, String& rpcMethod)
 {
 	Dictionary::Ptr message = JsonRpc::DecodeMessage(jsonString);
+	rpcMethod = message->Get("method");
+	if (rpcMethod.IsEmpty()) {
+		rpcMethod = "UNKNOWN";
+	}
 
 	if (m_Endpoint && message->Contains("ts")) {
 		double ts = message->Get("ts");

lib/remote/jsonrpcconnection.hpp

@@ -88,7 +88,23 @@ class JsonRpcConnection final : public Object
 	void CheckLiveness(boost::asio::yield_context yc);
 
 	bool ProcessMessage();
-	void MessageHandler(const String& jsonString);
+
+	/**
+	* MessageHandler routes the provided message to its corresponding handler (if any).
+	*
+	* This will first JSON decode the specified message and verifies the timestamp of that RPC message (if any).
+	* Subsequently, any message whose timestamp is less than the remote log position of the Endpoint will be rejected;
+	* otherwise, the endpoint's remote log position is updated to that timestamp. It is not expected to happen, but any
+	* message lacking an RPC method or referring to a non-existent one is also discarded. Afterwards, the RPC handler
+	* is then called for that message and sends it's result back to the sender if the message contains an ID.
+	*
+	* Note: The "rpcMethod" param is used as an output variable and is set to the RPC method of the given
+	* message if any, otherwise to "UNKNOWN".
+	*
+	* @param jsonString String The RPC message you want to process.
+	* @param rpcMethod String The output parameter for the RPC method.
+	*/
+	void MessageHandler(const String& jsonString, String& rpcMethod);
 
 	void CertificateRequestResponseHandler(const Dictionary::Ptr& message);