Merge branch 'feature/systemd-reload-6118' into next

Fixes #6118

icinga-app/icinga.cpp

@@ -161,7 +161,7 @@ static void SigHupHandler(int)
 }
 #endif /* _WIN32 */
 
-static bool Daemonize(const String& stderrFile)
+static bool Daemonize(void)
 {
 #ifndef _WIN32
 	pid_t pid = fork();
@@ -169,9 +169,39 @@ static bool Daemonize(const String& stderrFile)
 		return false;
 	}
 
-	if (pid)
-		exit(0);
+	if (pid) {
+		// systemd requires that the pidfile of the daemon is written before the forking
+		// process terminates. So wait till either the forked daemon has written a pidfile or died.
 
+		int status;
+		int ret;
+		pid_t readpid;
+		do {
+			Utility::Sleep(0.1);
+
+			readpid = Application::ReadPidFile(Application::GetPidPath());
+			ret = waitpid(pid, &status, WNOHANG);
+		} while (readpid != pid && ret == 0);
+
+		if (ret == pid) {
+			Log(LogCritical, "icinga-app", "The daemon could not be started. See logfile for details.");
+			exit(EXIT_FAILURE);
+		} else if (ret == -1) {
+			BOOST_THROW_EXCEPTION(posix_error()
+				<< boost::errinfo_api_function("waitpid")
+				<< boost::errinfo_errno(errno));
+		}
+
+		exit(0);
+	}
+#endif /* _WIN32 */
+
+	return true;
+}
+
+static bool SetDaemonIO(const String& stderrFile)
+{
+#ifndef _WIN32
 	int fdnull = open("/dev/null", O_RDWR);
 	if (fdnull >= 0) {
 		if (fdnull != 0)
@@ -484,12 +514,16 @@ int Main(void)
 	}
 
 	if (g_AppParams.count("daemonize")) {
-		String errorLog;
+		if (!g_AppParams.count("reload-internal")) {
+			// no additional fork neccessary on reload
+			Daemonize();
+		}
 
+		String errorLog;
 		if (g_AppParams.count("errorlog"))
 			errorLog = g_AppParams["errorlog"].as<std::string>();
 
-		Daemonize(errorLog);
+		SetDaemonIO(errorLog);
 		Logger::DisableConsoleLog();
 	}
 

lib/base/application.cpp

@@ -46,6 +46,7 @@ REGISTER_TYPE(Application);
 Application *Application::m_Instance = NULL;
 bool Application::m_ShuttingDown = false;
 bool Application::m_RequestRestart = false;
+pid_t Application::m_ReloadProcess = 0;
 static bool l_Restarting = false;
 bool Application::m_Debugging = false;
 int Application::m_ArgC;
@@ -91,7 +92,15 @@ void Application::Stop(void)
 	WSACleanup();
 #endif /* _WIN32 */
 
-	ClosePidFile();
+	// Getting a shutdown-signal when a restart is in progress usually
+	// means that the restart succeeded and the new process wants to take
+	// over. Write the PID of the new process to the pidfile before this
+	// process exits to keep systemd happy.
+	if (l_Restarting) {
+		UpdatePidFile(GetPidPath(), m_ReloadProcess);
+		ClosePidFile(false);
+	} else
+		ClosePidFile(true);
 
 	DynamicObject::Stop();
 }
@@ -218,7 +227,7 @@ void Application::SetArgV(char **argv)
  * Processes events for registered sockets and timers and calls whatever
  * handlers have been set up for these events.
  */
-void Application::RunEventLoop(void) const
+void Application::RunEventLoop(void)
 {
 	Timer::Initialize();
 
@@ -254,7 +263,7 @@ mainloop:
 			goto mainloop;
 
 		l_Restarting = true;
-		StartReloadProcess();
+		m_ReloadProcess = StartReloadProcess();
 
 		goto mainloop;
 	}
@@ -285,7 +294,7 @@ static void ReloadProcessCallback(const ProcessResult& pr)
 	l_Restarting = false;
 }
 
-void Application::StartReloadProcess(void) const
+pid_t Application::StartReloadProcess(void)
 {
 	Log(LogInformation, "base", "Got reload command: Starting new instance.");
 
@@ -305,6 +314,8 @@ void Application::StartReloadProcess(void) const
 	Process::Ptr process = make_shared<Process>(Process::PrepareCommand(args));
 	process->SetTimeout(300);
 	process->Run(&ReloadProcessCallback);
+ 
+	return process->GetPID();
 }
 
 /**
@@ -619,8 +630,9 @@ int Application::Run(void)
  * if the PID file is already locked by another instance of the application.
  *
  * @param filename The name of the PID file.
+ * @param pid The PID to write; default is the current PID
  */
-void Application::UpdatePidFile(const String& filename)
+void Application::UpdatePidFile(const String& filename, pid_t pid)
 {
 	ASSERT(!OwnsLock());
 	ObjectLock olock(this);
@@ -663,20 +675,27 @@ void Application::UpdatePidFile(const String& filename)
 	}
 #endif /* _WIN32 */
 
-	fprintf(m_PidFile, "%d\n", Utility::GetPid());
+	fprintf(m_PidFile, "%d\n", pid);
 	fflush(m_PidFile);
 }
 
 /**
  * Closes the PID file. Does nothing if the PID file is not currently open.
  */
-void Application::ClosePidFile(void)
+void Application::ClosePidFile(bool unlink)
 {
 	ASSERT(!OwnsLock());
 	ObjectLock olock(this);
 
 	if (m_PidFile != NULL)
+	{
+		if (unlink) {
+			String pidpath = GetPidPath();
+			::unlink(pidpath.CStr());
+		}
+
 		fclose(m_PidFile);
+	}
 
 	m_PidFile = NULL;
 }

lib/base/application.h

@@ -23,6 +23,7 @@
 #include "base/i2-base.h"
 #include "base/application.th"
 #include "base/threadpool.h"
+#include "base/utility.h"
 
 namespace icinga
 {
@@ -67,8 +68,8 @@ public:
 	static void SetDebugging(bool debug);
 	static bool IsDebugging(void);
 
-	void UpdatePidFile(const String& filename);
-	void ClosePidFile(void);
+	void UpdatePidFile(const String& filename, pid_t pid = Utility::GetPid());
+	void ClosePidFile(bool unlink);
 	static pid_t ReadPidFile(const String& filename);
 
 	static String GetExePath(const String& argv0);
@@ -113,9 +114,9 @@ protected:
 	virtual void OnConfigLoaded(void);
 	virtual void Stop(void);
 
-	void RunEventLoop(void) const;
+	void RunEventLoop(void);
 
-	void StartReloadProcess(void) const;
+	pid_t StartReloadProcess(void);
 
 	virtual void OnShutdown(void);
 
@@ -124,7 +125,10 @@ private:
 
 	static bool m_ShuttingDown; /**< Whether the application is in the process of
 				  shutting down. */
-	static bool m_RequestRestart;
+	static bool m_RequestRestart; /**< A restart was requested through SIGHUP */
+	static pid_t m_ReloadProcess; /**< The PID of a subprocess doing a reload, 
+									only valid when l_Restarting==true */
+
 	static int m_ArgC; /**< The number of command-line arguments. */
 	static char **m_ArgV; /**< Command-line arguments. */
 	FILE *m_PidFile; /**< The PID file */

lib/base/process.cpp

@@ -410,9 +410,10 @@ void Process::Run(const boost::function<void(const ProcessResult&)>& callback)
 
 	m_Process = pi.hProcess;
 	m_FD = outReadPipe;
+	m_PID = pi.dwProcessId;
 
 	Log(LogInformation, "base", "Running command '" + m_Arguments +
-		"': PID " + Convert::ToString(pi.dwProcessId));
+		"': PID " + Convert::ToString(m_PID));
 
 #else /* _WIN32 */
 	int fds[2];
@@ -514,8 +515,10 @@ void Process::Run(const boost::function<void(const ProcessResult&)>& callback)
 
 	// parent process
 
+	m_PID = m_Process;
+
 	Log(LogInformation, "base", "Running command '" + boost::algorithm::join(m_Arguments, " ") +
-		"': PID " + Convert::ToString(m_Process));
+		"': PID " + Convert::ToString(m_PID));
 
 	m_Arguments.clear();
 
@@ -636,6 +639,12 @@ bool Process::DoEvents(void)
 	return false;
 }
 
+pid_t Process::GetPID(void) const
+{
+	return m_PID;
+}
+
+
 int Process::GetTID(void) const
 {
 	return (reinterpret_cast<uintptr_t>(this) / sizeof(void *)) % IOTHREADS;

lib/base/process.h

@@ -73,6 +73,8 @@ public:
 
 	void Run(const boost::function<void (const ProcessResult&)>& callback = boost::function<void (const ProcessResult&)>());
 
+	pid_t GetPID(void) const;
+
 	static Arguments PrepareCommand(const Value& command);
 
 	static void StaticInitialize(void);
@@ -85,6 +87,7 @@ private:
 	double m_Timeout;
 
 	ProcessHandle m_Process;
+	pid_t m_PID;
 	ConsoleHandle m_FD;
 
 	std::ostringstream m_OutputStream;