threaded logging; sigsegv handler to flush logfile before crashing

servatrice/src/main.cpp

@@ -32,6 +32,7 @@
 
 RNG_Abstract *rng;
 ServerLogger *logger;
+ServerLoggerThread *loggerThread;
 
 void testRNG()
 {
@@ -72,6 +73,14 @@ void myMessageOutput(QtMsgType /*type*/, const char *msg)
 	logger->logMessage(msg);
 }
 
+void sigSegvHandler(int sig)
+{
+	logger->logMessage("SIGSEGV");
+	usleep(1000);
+	delete loggerThread;
+	raise(sig);
+}
+
 int main(int argc, char *argv[])
 {
 	QCoreApplication app(argc, argv);
@@ -86,7 +95,12 @@ int main(int argc, char *argv[])
 	QTextCodec::setCodecForCStrings(QTextCodec::codecForName("UTF-8"));
 	
 	QSettings *settings = new QSettings("servatrice.ini", QSettings::IniFormat);
-	logger = new ServerLogger(settings->value("server/logfile").toString());
+	
+	loggerThread = new ServerLoggerThread(settings->value("server/logfile").toString());
+	loggerThread->start();
+	loggerThread->waitForInit();
+	logger = loggerThread->getLogger();
+	
 	qInstallMsgHandler(myMessageOutput);
 #ifdef Q_OS_UNIX	
 	struct sigaction hup;
@@ -95,6 +109,12 @@ int main(int argc, char *argv[])
 	hup.sa_flags = 0;
 	hup.sa_flags |= SA_RESTART;
 	sigaction(SIGHUP, &hup, 0);
+	
+	struct sigaction segv;
+	segv.sa_handler = sigSegvHandler;
+	segv.sa_flags = SA_RESETHAND;
+	sigemptyset(&segv.sa_mask);
+	sigaction(SIGSEGV, &segv, 0);
 #endif
 	rng = new RNG_SFMT;
 	

servatrice/src/server_logger.cpp

@@ -3,17 +3,14 @@
 #include <QFile>
 #include <QTextStream>
 #include <QDateTime>
-#include <QThread>
-#ifdef Q_OS_UNIX
 #include <sys/types.h>
 #include <sys/socket.h>
-#endif
 
 ServerLogger::ServerLogger(const QString &logFileName, QObject *parent)
-	: QObject(parent)
+	: QObject(parent), flushRunning(false)
 {
 	if (!logFileName.isEmpty()) {
-		logFile = new QFile(logFileName, this);
+		logFile = new QFile("server.log", this);
 		logFile->open(QIODevice::Append);
 #ifdef Q_OS_UNIX
 		::socketpair(AF_UNIX, SOCK_STREAM, 0, sigHupFD);
@@ -22,6 +19,8 @@ ServerLogger::ServerLogger(const QString &logFileName, QObject *parent)
 		connect(snHup, SIGNAL(activated(int)), this, SLOT(handleSigHup()));
 	} else
 		logFile = 0;
+	
+	connect(this, SIGNAL(sigFlushBuffer()), this, SLOT(flushBuffer()), Qt::QueuedConnection);
 }
 
 ServerLogger::~ServerLogger()
@@ -33,11 +32,33 @@ void ServerLogger::logMessage(QString message)
 	if (!logFile)
 		return;
 	
-	logFileMutex.lock();
+	bufferMutex.lock();
+	buffer.append(QDateTime::currentDateTime().toString() + " " + QString::number((qulonglong) QThread::currentThread(), 16) + " " + message);
+	bufferMutex.unlock();
+	
+	emit sigFlushBuffer();
+}
+
+void ServerLogger::flushBuffer()
+{
+	if (flushRunning)
+		return;
+	
+	flushRunning = true;
 	QTextStream stream(logFile);
-	stream << QDateTime::currentDateTime().toString() << " " << ((void *) QThread::currentThread()) << " " << message << "\n";
+	forever {
-	stream.flush();
+		bufferMutex.lock();
-	logFileMutex.unlock();
+		if (buffer.isEmpty()) {
+			bufferMutex.unlock();
+			flushRunning = false;
+			return;
+		}
+		QString message = buffer.takeFirst();
+		bufferMutex.unlock();
+		
+		stream << message << "\n";
+		stream.flush();
+	}
 }
 
 void ServerLogger::hupSignalHandler(int /*unused*/)
@@ -66,3 +87,34 @@ void ServerLogger::handleSigHup()
 
 QFile *ServerLogger::logFile;
 int ServerLogger::sigHupFD[2];
+
+ServerLoggerThread::ServerLoggerThread(const QString &_fileName, QObject *parent)
+	: QThread(parent), fileName(_fileName)
+{
+}
+
+ServerLoggerThread::~ServerLoggerThread()
+{
+	quit();
+	wait();
+}
+
+void ServerLoggerThread::run()
+{
+	logger = new ServerLogger(fileName);
+	
+	usleep(100);
+	initWaitCondition.wakeAll();
+	
+	exec();
+	
+	delete logger;
+}
+
+void ServerLoggerThread::waitForInit()
+{
+	QMutex mutex;
+	mutex.lock();
+	initWaitCondition.wait(&mutex);
+	mutex.unlock();
+}

servatrice/src/server_logger.h

@@ -2,7 +2,10 @@
 #define SERVER_LOGGER_H
 
 #include <QObject>
+#include <QThread>
 #include <QMutex>
+#include <QWaitCondition>
+#include <QStringList>
 
 class QSocketNotifier;
 class QFile;
@@ -17,11 +20,31 @@ public slots:
 	void logMessage(QString message);
 private slots:
 	void handleSigHup();
+	void flushBuffer();
+signals:
+	void sigFlushBuffer();
 private:
 	static int sigHupFD[2];
 	QSocketNotifier *snHup;
 	static QFile *logFile;
-	QMutex logFileMutex;
+	bool flushRunning;
+	QStringList buffer;
+	QMutex bufferMutex;
+};
+
+class ServerLoggerThread : public QThread {
+	Q_OBJECT
+private:
+	QString fileName;
+	ServerLogger *logger;
+	QWaitCondition initWaitCondition;
+protected:
+	void run();
+public:
+	ServerLoggerThread(const QString &_fileName, QObject *parent = 0);
+	~ServerLoggerThread();
+	ServerLogger *getLogger() const { return logger; }
+	void waitForInit();
 };
 
 #endif