Add flush_threshold/flush_interval logic to GelfWriter

doc/09-object-types.md

@@ -1317,6 +1317,8 @@ Configuration Attributes:
   diconnect\_timeout        | Duration              | **Optional.** Timeout to wait for any outstanding data to be flushed to GELF before disconnecting. Defaults to `10s`.
   source                    | String                | **Optional.** Source name for this instance. Defaults to `icinga2`.
   enable\_send\_perfdata    | Boolean               | **Optional.** Enable performance data for 'CHECK RESULT' events.
+  flush\_interval           | Duration              | **Optional.** How long to buffer data points before sending. Defaults to `15s`.
+  flush\_threshold          | Number                | **Optional.** How many bytes to buffer before forcing a flush to the backend. Defaults to `2MiB`.
   enable\_ha                | Boolean               | **Optional.** Enable the high availability functionality. Only valid in a [cluster setup](06-distributed-monitoring.md#distributed-monitoring-high-availability-features). Defaults to `false`.
   enable\_tls               | Boolean               | **Optional.** Whether to use a TLS stream. Defaults to `false`.
   insecure\_noverify        | Boolean               | **Optional.** Disable TLS peer verification.

lib/perfdata/gelfwriter.cpp

@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include "perfdata/gelfwriter.hpp"
+#include "base/defer.hpp"
 #include "perfdata/gelfwriter-ti.cpp"
 #include "icinga/service.hpp"
 #include "icinga/notification.hpp"
@@ -90,6 +91,13 @@ void GelfWriter::Resume()
 	/* Register exception handler for WQ tasks. */
 	m_WorkQueue.SetExceptionCallback([this](boost::exception_ptr exp) { ExceptionHandler(std::move(exp)); });
 
+	/* Setup timer for periodically flushing m_DataBuffer */
+	m_FlushTimer = Timer::Create();
+	m_FlushTimer->SetInterval(GetFlushInterval());
+	m_FlushTimer->OnTimerExpired.connect([this](const Timer * const&) { FlushTimeout(); });
+	m_FlushTimer->Start();
+	m_FlushTimer->Reschedule(0);
+
 	m_Connection = new PerfdataWriterConnection{this, GetHost(), GetPort(), m_SslContext, !GetInsecureNoverify()};
 
 	/* Register event handlers. */
@@ -115,6 +123,8 @@ void GelfWriter::Pause()
 	m_HandleNotifications.disconnect();
 	m_HandleStateChanges.disconnect();
 
+	m_FlushTimer->Stop(true);
+
 	std::promise<void> queueDonePromise;
 
 	m_WorkQueue.Enqueue([&]() {
@@ -360,19 +370,38 @@ void GelfWriter::SendLogMessage(const Checkable::Ptr& checkable, const String& g
 {
 	AssertOnWorkQueue();
 
-	std::ostringstream msgbuf;
-	msgbuf << gelfMessage;
-	msgbuf << '\0';
+	Log(LogDebug, "GelfWriter")
+		<< "Checkable '" << checkable->GetName() << "' sending message '" << gelfMessage << "'.";
 
-	auto log = msgbuf.str();
+	m_MsgBuf.GetData().reserve(m_MsgBuf.GetLength() + gelfMessage.GetLength() + 1);
+	m_MsgBuf += gelfMessage;
+	m_MsgBuf += '\0';
 
-	try {
-		Log(LogDebug, "GelfWriter")
-			<< "Checkable '" << checkable->GetName() << "' sending message '" << log << "'.";
-
-		m_Connection->Send(boost::asio::const_buffer{log.data(), log.length()});
-	} catch (const PerfdataWriterConnection::Stopped& ex) {
-		Log(LogDebug, "GelfWriter") << ex.what();
-		return;
+	if (GetFlushThreshold() <= m_MsgBuf.GetLength()) {
+		Flush();
+	}
+}
+
+/**
+ * Queues a Flush on the work-queue if none is queued yet.
+ */
+void GelfWriter::FlushTimeout()
+{
+	if (m_FlushTimerInQueue.exchange(true, std::memory_order_relaxed)) {
+		return;
+	}
+
+	m_WorkQueue.Enqueue([&]() {
+		Defer resetFlushTimer{[&]() { m_FlushTimerInQueue.store(false, std::memory_order_relaxed); }};
+		Flush();
+	});
+}
+
+void GelfWriter::Flush()
+{
+	try {
+		m_Connection->Send(boost::asio::buffer(std::exchange(m_MsgBuf.GetData(), {})));
+	} catch (const PerfdataWriterConnection::Stopped& ex) {
+		Log(LogDebug, "GelfWriter") << ex.what();
 	}
 }

lib/perfdata/gelfwriter.hpp

@@ -34,6 +34,9 @@ protected:
 
 private:
 	PerfdataWriterConnection::Ptr m_Connection;
+	Timer::Ptr m_FlushTimer;
+	std::atomic_bool m_FlushTimerInQueue{false};
+	String m_MsgBuf;
 	WorkQueue m_WorkQueue{10000000, 1};
 	Shared<boost::asio::ssl::context>::Ptr m_SslContext;
 
@@ -46,6 +49,8 @@ private:
 
 	String ComposeGelfMessage(const Dictionary::Ptr& fields, const String& source, double ts);
 	void SendLogMessage(const Checkable::Ptr& checkable, const String& gelfMessage);
+	void FlushTimeout();
+	void Flush();
 
 	void AssertOnWorkQueue();
 

lib/perfdata/gelfwriter.ti

@@ -24,6 +24,12 @@ class GelfWriter : ConfigObject
 	[config] bool enable_send_perfdata {
 		default {{{ return false; }}}
 	};
+	[config] int flush_interval {
+		default {{{ return 15; }}}
+	};
+	[config] std::size_t flush_threshold {
+		default {{{ return 2 * 1024 * 1024; }}}
+	};
 
 	[config] double disconnect_timeout {
 		default {{{ return 10; }}}