From 33781496daa3a1863583874ae8c8555d5dd6f51a Mon Sep 17 00:00:00 2001
From: Julian Brost <julian.brost@icinga.com>
Date: Thu, 16 Dec 2021 14:49:50 +0100
Subject: [PATCH] InfluxdbCommonWriter: use atomic_size_t to data buffer size
 from stats function

m_DataBuffer may be modified concurrently while StatsFunc() is called, thus
it's unsafe to call size() on it. As write access to m_DataBuffer is already
synchronized by only modifying it from the single work queue thread, instead of
adding a mutex, this commit adds a new std::atomic_size_t which is additionally
updated when modifying m_DataBuffer and can safely be accessed in StatsFunc().
---
 lib/perfdata/influxdbcommonwriter.cpp | 2 ++
 lib/perfdata/influxdbcommonwriter.hpp | 4 +++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/perfdata/influxdbcommonwriter.cpp b/lib/perfdata/influxdbcommonwriter.cpp
index 071abae93..98eb453b7 100644
--- a/lib/perfdata/influxdbcommonwriter.cpp
+++ b/lib/perfdata/influxdbcommonwriter.cpp
@@ -402,6 +402,7 @@ void InfluxdbCommonWriter::SendMetric(const Checkable::Ptr& checkable, const Dic
 
 	// Buffer the data point
 	m_DataBuffer.emplace_back(msgbuf.str());
+	m_DataBufferSize = m_DataBuffer.size();
 
 	// Flush if we've buffered too much to prevent excessive memory use
 	if (static_cast<int>(m_DataBuffer.size()) >= GetFlushThreshold()) {
@@ -447,6 +448,7 @@ void InfluxdbCommonWriter::FlushWQ()
 
 	String body = boost::algorithm::join(m_DataBuffer, "\n");
 	m_DataBuffer.clear();
+	m_DataBufferSize = 0;
 
 	OptionalTlsStream stream;
 
diff --git a/lib/perfdata/influxdbcommonwriter.hpp b/lib/perfdata/influxdbcommonwriter.hpp
index ad47e6100..791a326b4 100644
--- a/lib/perfdata/influxdbcommonwriter.hpp
+++ b/lib/perfdata/influxdbcommonwriter.hpp
@@ -14,6 +14,7 @@
 #include "remote/url.hpp"
 #include <boost/beast/http/message.hpp>
 #include <boost/beast/http/string_body.hpp>
+#include <atomic>
 #include <fstream>
 
 namespace icinga
@@ -49,6 +50,7 @@ private:
 	Timer::Ptr m_FlushTimer;
 	WorkQueue m_WorkQueue{10000000, 1};
 	std::vector<String> m_DataBuffer;
+	std::atomic_size_t m_DataBufferSize{0};
 
 	void CheckResultHandler(const Checkable::Ptr& checkable, const CheckResult::Ptr& cr);
 	void CheckResultHandlerWQ(const Checkable::Ptr& checkable, const CheckResult::Ptr& cr);
@@ -77,7 +79,7 @@ void InfluxdbCommonWriter::StatsFunc(const Dictionary::Ptr& status, const Array:
 	for (const typename InfluxWriter::Ptr& influxwriter : ConfigType::GetObjectsByType<InfluxWriter>()) {
 		size_t workQueueItems = influxwriter->m_WorkQueue.GetLength();
 		double workQueueItemRate = influxwriter->m_WorkQueue.GetTaskCount(60) / 60.0;
-		size_t dataBufferItems = influxwriter->m_DataBuffer.size();
+		size_t dataBufferItems = influxwriter->m_DataBufferSize;
 
 		nodes.emplace_back(influxwriter->GetName(), new Dictionary({
 			{ "work_queue_items", workQueueItems },