logging improvements (#664)

* Eliminate spurious `FlushFileBuffers` calls on Windows by tracking writes
* Make cache log file creation optional

4 files changed, 34 insertions, 21 deletions

diff --git a/src/zenserver/diag/logging.cpp b/src/zenserver/diag/logging.cpp
index 90af79651..80da240e8 100644
--- a/src/zenserver/diag/logging.cpp
+++ b/src/zenserver/diag/logging.cpp
@@ -21,7 +21,7 @@ ZEN_THIRD_PARTY_INCLUDES_END
 namespace zen {
 
 void
-InitializeServerLogging(const ZenServerConfig& InOptions)
+InitializeServerLogging(const ZenServerConfig& InOptions, bool WithCacheService)
 {
 	ZEN_MEMSCOPE(ELLMTag::Logging);
 
@@ -51,29 +51,32 @@ InitializeServerLogging(const ZenServerConfig& InOptions)
 	spdlog::apply_logger_env_levels(HttpLogger);
 	spdlog::register_logger(HttpLogger);
 
-	// Cache request logging
-	std::filesystem::path CacheLogPath = InOptions.DataDir / "logs" / "z$.log";
-	zen::CreateDirectories(CacheLogPath.parent_path());
+	if (WithCacheService)
+	{
+		// Cache request logging
+		std::filesystem::path CacheLogPath = InOptions.DataDir / "logs" / "z$.log";
+		zen::CreateDirectories(CacheLogPath.parent_path());
 
-	auto CacheSink	 = std::make_shared<zen::logging::RotatingFileSink>(CacheLogPath,
-																		/* max size */ 128 * 1024 * 1024,
-																		/* max files */ 16,
-																		/* rotate on open */ false);
-	auto CacheLogger = std::make_shared<spdlog::logger>("z$", CacheSink);
-	spdlog::apply_logger_env_levels(CacheLogger);
-	spdlog::register_logger(CacheLogger);
+		auto CacheSink	 = std::make_shared<zen::logging::RotatingFileSink>(CacheLogPath,
+																			/* max size */ 128 * 1024 * 1024,
+																			/* max files */ 16,
+																			/* rotate on open */ false);
+		auto CacheLogger = std::make_shared<spdlog::logger>("z$", CacheSink);
+		spdlog::apply_logger_env_levels(CacheLogger);
+		spdlog::register_logger(CacheLogger);
 
-	// Jupiter - only log upstream HTTP traffic to file
+		// Jupiter - only log upstream HTTP traffic to file
 
-	auto JupiterLogger = std::make_shared<spdlog::logger>("jupiter", FileSink);
-	spdlog::apply_logger_env_levels(JupiterLogger);
-	spdlog::register_logger(JupiterLogger);
+		auto JupiterLogger = std::make_shared<spdlog::logger>("jupiter", FileSink);
+		spdlog::apply_logger_env_levels(JupiterLogger);
+		spdlog::register_logger(JupiterLogger);
 
-	// Zen - only log upstream HTTP traffic to file
+		// Zen - only log upstream HTTP traffic to file
 
-	auto ZenClientLogger = std::make_shared<spdlog::logger>("zenclient", FileSink);
-	spdlog::apply_logger_env_levels(ZenClientLogger);
-	spdlog::register_logger(ZenClientLogger);
+		auto ZenClientLogger = std::make_shared<spdlog::logger>("zenclient", FileSink);
+		spdlog::apply_logger_env_levels(ZenClientLogger);
+		spdlog::register_logger(ZenClientLogger);
+	}
 
 	//
 
diff --git a/src/zenserver/diag/logging.h b/src/zenserver/diag/logging.h
index 4b27a50cf..9a85eb719 100644
--- a/src/zenserver/diag/logging.h
+++ b/src/zenserver/diag/logging.h
@@ -8,7 +8,7 @@ namespace zen {
 
 struct ZenServerConfig;
 
-void InitializeServerLogging(const ZenServerConfig& LogOptions);
+void InitializeServerLogging(const ZenServerConfig& LogOptions, bool WithCacheService);
 void ShutdownServerLogging();
 
 }  // namespace zen
diff --git a/src/zenserver/zenserver.cpp b/src/zenserver/zenserver.cpp
index 5408f2f0b..e83624bbb 100644
--- a/src/zenserver/zenserver.cpp
+++ b/src/zenserver/zenserver.cpp
@@ -505,7 +505,7 @@ ZenServerMain::Run()
 			}
 		}
 
-		InitializeServerLogging(m_ServerOptions);
+		InitializeServerLogging(m_ServerOptions, /* WithCacheService */ true);
 
 		ZEN_INFO("Command line: {}", m_ServerOptions.CommandLine);
 
diff --git a/src/zenutil/include/zenutil/logging/rotatingfilesink.h b/src/zenutil/include/zenutil/logging/rotatingfilesink.h
index 5c6c655b8..4d10f3794 100644
--- a/src/zenutil/include/zenutil/logging/rotatingfilesink.h
+++ b/src/zenutil/include/zenutil/logging/rotatingfilesink.h
@@ -114,6 +114,11 @@ public:
 	}
 	virtual void flush() override
 	{
+		if (!m_NeedFlush)
+		{
+			return;
+		}
+
 		ZEN_MEMSCOPE(ELLMTag::Logging);
 
 		try
@@ -128,6 +133,8 @@ public:
 		{
 			// Silently eat errors
 		}
+
+		m_NeedFlush = false;
 	}
 
 	virtual void set_pattern(const std::string& pattern) override
@@ -204,6 +211,7 @@ private:
 		{
 			return false;
 		}
+		m_NeedFlush = true;
 		return true;
 	}
 
@@ -229,6 +237,7 @@ private:
 		{
 			return false;
 		}
+		m_NeedFlush = true;
 		return true;
 	}
 
@@ -239,6 +248,7 @@ private:
 	const std::size_t				   m_MaxSize;
 	const std::size_t				   m_MaxFiles;
 	BasicFile						   m_CurrentFile;
+	bool							   m_NeedFlush = false;
 };
 
 }  // namespace zen::logging