/*
 * PgArchiverMain
 *
 *	The argc/argv parameters are valid only in EXEC_BACKEND case.  However,
 *	since we don't use 'em, it hardly matters...
 */
NON_EXEC_STATIC void
PgArchiverMain(int argc, char *argv[])
{
	/*
	 * Ignore all signals usually bound to some action in the postmaster,
	 * except for SIGHUP, SIGTERM, SIGUSR1, SIGUSR2, and SIGQUIT.
	 */
	pqsignal(SIGHUP, ArchSigHupHandler);
	pqsignal(SIGINT, SIG_IGN);
	pqsignal(SIGTERM, ArchSigTermHandler);
	pqsignal(SIGQUIT, pgarch_exit);
	pqsignal(SIGALRM, SIG_IGN);
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, pgarch_waken);
	pqsignal(SIGUSR2, pgarch_waken_stop);
	pqsignal(SIGCHLD, SIG_DFL);
	pqsignal(SIGTTIN, SIG_DFL);
	pqsignal(SIGTTOU, SIG_DFL);
	pqsignal(SIGCONT, SIG_DFL);
	pqsignal(SIGWINCH, SIG_DFL);
	PG_SETMASK(&UnBlockSig);

	/*
	 * Identify myself via ps
	 */
	init_ps_display("archiver process", "", "", "");

	pgarch_MainLoop();

	exit(0);
}

/*
 * WalSndQuickDieHandler() occurs when signalled SIGQUIT by the postmaster.
 *
 * Some backend has bought the farm,
 * so we need to stop what we're doing and exit.
 */
static void
WalSndQuickDieHandler(SIGNAL_ARGS)
{
	PG_SETMASK(&BlockSig);

	/*
	 * We DO NOT want to run proc_exit() callbacks -- we're here because
	 * shared memory may be corrupted, so we don't want to try to clean up our
	 * transaction.  Just nail the windows shut and get out of town.  Now that
	 * there's an atexit callback to prevent third-party code from breaking
	 * things by calling exit() directly, we have to reset the callbacks
	 * explicitly to make this work as intended.
	 */
	on_exit_reset();

	/*
	 * Note we do exit(2) not exit(0).	This is to force the postmaster into a
	 * system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
	 * backend.  This is necessary precisely because we don't clean up our
	 * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
	 * should ensure the postmaster sees this as a crash, too, but no harm in
	 * being doubly sure.)
	 */
	exit(2);
}

/* Main entry point for walsender process */
int
WalSenderMain(void)
{
	MemoryContext walsnd_context;

	am_cascading_walsender = RecoveryInProgress();

	/* Create a per-walsender data structure in shared memory */
	InitWalSnd();

	/*
	 * Create a memory context that we will do all our work in.  We do this so
	 * that we can reset the context during error recovery and thereby avoid
	 * possible memory leaks.  Formerly this code just ran in
	 * TopMemoryContext, but resetting that would be a really bad idea.
	 *
	 * XXX: we don't actually attempt error recovery in walsender, we just
	 * close the connection and exit.
	 */
	walsnd_context = AllocSetContextCreate(TopMemoryContext,
										   "Wal Sender",
										   ALLOCSET_DEFAULT_MINSIZE,
										   ALLOCSET_DEFAULT_INITSIZE,
										   ALLOCSET_DEFAULT_MAXSIZE);
	MemoryContextSwitchTo(walsnd_context);

	/* Set up resource owner */
	CurrentResourceOwner = ResourceOwnerCreate(NULL, "walsender top-level resource owner");

	/* Unblock signals (they were blocked when the postmaster forked us) */
	PG_SETMASK(&UnBlockSig);

	/*
	 * Use the recovery target timeline ID during recovery
	 */
	if (am_cascading_walsender)
		ThisTimeLineID = GetRecoveryTargetTLI();

	/* Tell the standby that walsender is ready for receiving commands */
	ReadyForQuery(DestRemote);

	/* Handle handshake messages before streaming */
	WalSndHandshake();

	/* Initialize shared memory status */
	{
		/* use volatile pointer to prevent code rearrangement */
		volatile WalSnd *walsnd = MyWalSnd;

		SpinLockAcquire(&walsnd->mutex);
		walsnd->sentPtr = sentPtr;
		SpinLockRelease(&walsnd->mutex);
	}

	SyncRepInitConfig();

	/* Main loop of walsender */
	return WalSndLoop();
}

/* ----------------------------------
 *	Startup Process main entry point
 * ----------------------------------
 */
void
StartupProcessMain(void)
{
	/*
	 * If possible, make this process a group leader, so that the postmaster
	 * can signal any child processes too.
	 */
#ifdef HAVE_SETSID
	if (setsid() < 0)
		elog(FATAL, "setsid() failed: %m");
#endif

	/*
	 * Properly accept or ignore signals the postmaster might send us.
	 */
	pqsignal(SIGHUP, StartupProcSigHupHandler); /* reload config file */
	pqsignal(SIGINT, SIG_IGN);	/* ignore query cancel */
	pqsignal(SIGTERM, StartupProcShutdownHandler);		/* request shutdown */
	pqsignal(SIGQUIT, startupproc_quickdie);	/* hard crash time */
	InitializeTimeouts();		/* establishes SIGALRM handler */
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, StartupProcSigUsr1Handler);
	pqsignal(SIGUSR2, StartupProcTriggerHandler);

	/*
	 * Reset some signals that are accepted by postmaster but not here
	 */
	pqsignal(SIGCHLD, SIG_DFL);
	pqsignal(SIGTTIN, SIG_DFL);
	pqsignal(SIGTTOU, SIG_DFL);
	pqsignal(SIGCONT, SIG_DFL);
	pqsignal(SIGWINCH, SIG_DFL);

	/*
	 * Register timeouts needed for standby mode
	 */
	RegisterTimeout(STANDBY_DEADLOCK_TIMEOUT, StandbyDeadLockHandler);
	RegisterTimeout(STANDBY_TIMEOUT, StandbyTimeoutHandler);

	/*
	 * Unblock signals (they were blocked when the postmaster forked us)
	 */
	PG_SETMASK(&UnBlockSig);

	/*
	 * Do what we came for.
	 */
	StartupXLOG();

	/*
	 * Exit normally. Exit code 0 tells postmaster that we completed recovery
	 * successfully.
	 */
	proc_exit(0);
}

/*
 * resetTimers - disable process interval timers
 *
 * Testing has shown that fork on some systems doesn't clear timers as it should and
 * exec is subjected to *fatal* interruption by timers so the timers are disabled
 * before the fork is done.  Before resetting the interval timers, the all signals
 * are blocked.  After resetting the interval timers, the signal mask is restored.
 *
 * otimers: a pointer to an itmers struct to contain the old timer values.  If
 * 		NULL, the old timer valuess are not preserved.
 *
 * Errors from setitimer are not expected and are handled using Assert (as in
 * PGSempahoreLockTimed).
 */
void
resetTimers(struct itimers *otimers)
{
	int			err;
	struct itimerval xtimer;	/* Zero timer for disabling */
	struct itimerval *p_rtimer = NULL;	/* ITIMER_REAL */
	struct itimerval *p_vtimer = NULL;	/* ITIMER_VIRTUAL */
	struct itimerval *p_ptimer = NULL;	/* ITIMER_PROF */

	if (otimers != NULL)
	{
		p_rtimer = &otimers->rtimer;
		p_vtimer = &otimers->vtimer;
		p_ptimer = &otimers->ptimer;
	}

	/*
	 * Block signals while capturing timers.
	 */
	PG_SETMASK(&BlockSig);

	/*
	 * Disable all process interval timers preserving the old values if
	 * requested.
	 */
	timerclear(&xtimer.it_interval);
	timerclear(&xtimer.it_value);

	err = setitimer(ITIMER_REAL, &xtimer, p_rtimer);
	Assert(err == 0);

	err = setitimer(ITIMER_VIRTUAL, &xtimer, p_vtimer);
	Assert(err == 0);

	err = setitimer(ITIMER_REAL, &xtimer, p_ptimer);
	Assert(err == 0);

	/*
	 * Restore signal mask.
	 */
	PG_SETMASK(&UnBlockSig);
}

/* Main entry point for walsender process */
int
WalSenderMain(void)
{
	MemoryContext walsnd_context;

	if (RecoveryInProgress())
		ereport(FATAL,
				(errcode(ERRCODE_CANNOT_CONNECT_NOW),
				 errmsg("recovery is still in progress, can't accept WAL streaming connections")));

	/* Create a per-walsender data structure in shared memory */
	InitWalSnd();

	/*
	 * Create a memory context that we will do all our work in.  We do this so
	 * that we can reset the context during error recovery and thereby avoid
	 * possible memory leaks.  Formerly this code just ran in
	 * TopMemoryContext, but resetting that would be a really bad idea.
	 *
	 * XXX: we don't actually attempt error recovery in walsender, we just
	 * close the connection and exit.
	 */
	walsnd_context = AllocSetContextCreate(TopMemoryContext,
										   "Wal Sender",
										   ALLOCSET_DEFAULT_MINSIZE,
										   ALLOCSET_DEFAULT_INITSIZE,
										   ALLOCSET_DEFAULT_MAXSIZE);
	MemoryContextSwitchTo(walsnd_context);

	/* Unblock signals (they were blocked when the postmaster forked us) */
	PG_SETMASK(&UnBlockSig);

	/* Tell the standby that walsender is ready for receiving commands */
	ReadyForQuery(DestRemote);

	/* Handle handshake messages before streaming */
	WalSndHandshake();

	/* Initialize shared memory status */
	{
		/* use volatile pointer to prevent code rearrangement */
		volatile WalSnd *walsnd = MyWalSnd;

		SpinLockAcquire(&walsnd->mutex);
		walsnd->sentPtr = sentPtr;
		SpinLockRelease(&walsnd->mutex);
	}

	/* Main loop of walsender */
	return WalSndLoop();
}

/*
 * PgArchiverMain
 *
 *	The argc/argv parameters are valid only in EXEC_BACKEND case.  However,
 *	since we don't use 'em, it hardly matters...
 */
NON_EXEC_STATIC void
PgArchiverMain(int argc, char *argv[])
{
	IsUnderPostmaster = true;	/* we are a postmaster subprocess now */

	MyProcPid = getpid();		/* reset MyProcPid */

	MyStartTime = time(NULL);	/* record Start Time for logging */

	/*
	 * If possible, make this process a group leader, so that the postmaster
	 * can signal any child processes too.
	 */
#ifdef HAVE_SETSID
	if (setsid() < 0)
		elog(FATAL, "setsid() failed: %m");
#endif

	InitializeLatchSupport();	/* needed for latch waits */

	InitLatch(&mainloop_latch); /* initialize latch used in main loop */

	/*
	 * Ignore all signals usually bound to some action in the postmaster,
	 * except for SIGHUP, SIGTERM, SIGUSR1, SIGUSR2, and SIGQUIT.
	 */
	pqsignal(SIGHUP, ArchSigHupHandler);
	pqsignal(SIGINT, SIG_IGN);
	pqsignal(SIGTERM, ArchSigTermHandler);
	pqsignal(SIGQUIT, pgarch_exit);
	pqsignal(SIGALRM, SIG_IGN);
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, pgarch_waken);
	pqsignal(SIGUSR2, pgarch_waken_stop);
	pqsignal(SIGCHLD, SIG_DFL);
	pqsignal(SIGTTIN, SIG_DFL);
	pqsignal(SIGTTOU, SIG_DFL);
	pqsignal(SIGCONT, SIG_DFL);
	pqsignal(SIGWINCH, SIG_DFL);
	PG_SETMASK(&UnBlockSig);

	/*
	 * Identify myself via ps
	 */
	init_ps_display("archiver process", "", "", "");

	pgarch_MainLoop();

	exit(0);
}

/*
 * bg_quickdie() occurs when signalled SIGQUIT by the postmaster.
 *
 * Some backend has bought the farm,
 * so we need to stop what we're doing and exit.
 */
static void
bg_quickdie(SIGNAL_ARGS)
{
	PG_SETMASK(&BlockSig);

	/*
	 * DO NOT proc_exit() -- we're here because shared memory may be
	 * corrupted, so we don't want to try to clean up our transaction. Just
	 * nail the windows shut and get out of town.
	 *
	 * Note we do exit(2) not exit(0).	This is to force the postmaster into a
	 * system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
	 * backend.  This is necessary precisely because we don't clean up our
	 * shared memory state.
	 */
	exit(2);
}

/*
 * ServiceQuickDie() occurs when signalled SIGQUIT by the postmaster.
 *
 * Some backend has bought the farm,
 * so we need to stop what we're doing and exit.
 */
static void
ServiceQuickDie(SIGNAL_ARGS)
{
	PG_SETMASK(&BlockSig);

	ereport(LOG,
			(errmsg("terminating immediately")));


	/* DO ANY SPECIAL SERVICE QUICKDIE HANDLING HERE */

	/*
	 * NOTE: see MPP-9518, MPP-9396, we need to make sure the atexit()
	 * hooks get cleaned up before calling exit(). quickdie() knows how
	 * to do that.
	 */
	quickdie(PASS_SIGNAL_ARGS);
	/* not reached */
}

/*
 * PgArchiverMain
 *
 *	The argc/argv parameters are valid only in EXEC_BACKEND case.  However,
 *	since we don't use 'em, it hardly matters...
 */
NON_EXEC_STATIC void
PgArchiverMain(int argc, char *argv[])
{
	IsUnderPostmaster = true;	/* we are a postmaster subprocess now */

	MyProcPid = getpid();		/* reset MyProcPid */

	/* Lose the postmaster's on-exit routines */
	on_exit_reset();

	/*
	 * Ignore all signals usually bound to some action in the postmaster,
	 * except for SIGHUP, SIGUSR1 and SIGQUIT.
	 */
	pqsignal(SIGHUP, ArchSigHupHandler);
	pqsignal(SIGINT, SIG_IGN);
	pqsignal(SIGTERM, SIG_IGN);
	pqsignal(SIGQUIT, pgarch_exit);
	pqsignal(SIGALRM, SIG_IGN);
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, pgarch_waken);
	pqsignal(SIGUSR2, SIG_IGN);
	pqsignal(SIGCHLD, SIG_DFL);
	pqsignal(SIGTTIN, SIG_DFL);
	pqsignal(SIGTTOU, SIG_DFL);
	pqsignal(SIGCONT, SIG_DFL);
	pqsignal(SIGWINCH, SIG_DFL);
	PG_SETMASK(&UnBlockSig);

	/*
	 * Identify myself via ps
	 */
	init_ps_display("archiver process", "", "");
	set_ps_display("");

	pgarch_MainLoop();

	exit(0);
}

//.........这里部分代码省略.........
#endif

	InitializeLatchSupport();	/* needed for latch waits */

	/* Initialize private latch for use by signal handlers */
	InitLatch(&sysLoggerLatch);

	/*
	 * Properly accept or ignore signals the postmaster might send us
	 *
	 * Note: we ignore all termination signals, and instead exit only when all
	 * upstream processes are gone, to ensure we don't miss any dying gasps of
	 * broken backends...
	 */

	pqsignal(SIGHUP, sigHupHandler);	/* set flag to read config file */
	pqsignal(SIGINT, SIG_IGN);
	pqsignal(SIGTERM, SIG_IGN);
	pqsignal(SIGQUIT, SIG_IGN);
	pqsignal(SIGALRM, SIG_IGN);
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, sigUsr1Handler);	/* request log rotation */
	pqsignal(SIGUSR2, SIG_IGN);

	/*
	 * Reset some signals that are accepted by postmaster but not here
	 */
	pqsignal(SIGCHLD, SIG_DFL);
	pqsignal(SIGTTIN, SIG_DFL);
	pqsignal(SIGTTOU, SIG_DFL);
	pqsignal(SIGCONT, SIG_DFL);
	pqsignal(SIGWINCH, SIG_DFL);

	PG_SETMASK(&UnBlockSig);

#ifdef WIN32
	/* Fire up separate data transfer thread */
	InitializeCriticalSection(&sysloggerSection);
	EnterCriticalSection(&sysloggerSection);

	threadHandle = (HANDLE) _beginthreadex(NULL, 0, pipeThread, NULL, 0, NULL);
	if (threadHandle == 0)
		elog(FATAL, "could not create syslogger data transfer thread: %m");
#endif   /* WIN32 */

	/*
	 * Remember active logfile's name.  We recompute this from the reference
	 * time because passing down just the pg_time_t is a lot cheaper than
	 * passing a whole file path in the EXEC_BACKEND case.
	 */
	last_file_name = logfile_getname(first_syslogger_file_time, NULL);

	/* remember active logfile parameters */
	currentLogDir = pstrdup(Log_directory);
	currentLogFilename = pstrdup(Log_filename);
	currentLogRotationAge = Log_RotationAge;
	/* set next planned rotation time */
	set_next_rotation_time();

	/* main worker loop */
	for (;;)
	{
		bool		time_based_rotation = false;
		int			size_rotation_for = 0;
		long		cur_timeout;
		int			cur_flags;

//.........这里部分代码省略.........
		 * Now return to normal top-level context and clear ErrorContext for
		 * next time.
		 */
		MemoryContextSwitchTo(bgwriter_context);
		FlushErrorState();

		/* Flush any leaked data in the top-level context */
		MemoryContextResetAndDeleteChildren(bgwriter_context);

		/* Now we can allow interrupts again */
		RESUME_INTERRUPTS();

		/*
		 * Sleep at least 1 second after any error.  A write error is likely
		 * to be repeated, and we don't want to be filling the error logs as
		 * fast as we can.
		 */
		pg_usleep(1000000L);

		/*
		 * Close all open files after any error.  This is helpful on Windows,
		 * where holding deleted files open causes various strange errors.
		 * It's not clear we need it elsewhere, but shouldn't hurt.
		 */
		smgrcloseall();
	}

	/* We can now handle ereport(ERROR) */
	PG_exception_stack = &local_sigjmp_buf;

	/*
	 * Unblock signals (they were blocked when the postmaster forked us)
	 */
	PG_SETMASK(&UnBlockSig);

	/*
	 * Loop forever
	 */
	for (;;)
	{
		bool		do_checkpoint = false;
		int			flags = 0;
		time_t		now;
		int			elapsed_secs;

		/*
		 * Emergency bailout if postmaster has died.  This is to avoid the
		 * necessity for manual cleanup of all postmaster children.
		 */
		if (!PostmasterIsAlive(true))
			exit(1);

		/*
		 * Process any requests or signals received recently.
		 */
		AbsorbFsyncRequests();

		if (got_SIGHUP)
		{
			got_SIGHUP = false;
			ProcessConfigFile(PGC_SIGHUP);
		}
		if (checkpoint_requested)
		{
			checkpoint_requested = false;
			do_checkpoint = true;

//.........这里部分代码省略.........
		 * AbortTransaction().	We don't have very many resources to worry
		 * about in walwriter, but we do have LWLocks, and perhaps buffers?
		 */
		LWLockReleaseAll();
		AbortBufferIO();
		UnlockBuffers();
		/* buffer pins are released here: */
		ResourceOwnerRelease(CurrentResourceOwner,
							 RESOURCE_RELEASE_BEFORE_LOCKS,
							 false, true);
		/* we needn't bother with the other ResourceOwnerRelease phases */
		AtEOXact_Buffers(false);
		AtEOXact_Files();
		AtEOXact_HashTables(false);

		/*
		 * Now return to normal top-level context and clear ErrorContext for
		 * next time.
		 */
		MemoryContextSwitchTo(walwriter_context);
		FlushErrorState();

		/* Flush any leaked data in the top-level context */
		MemoryContextResetAndDeleteChildren(walwriter_context);

		/* Now we can allow interrupts again */
		RESUME_INTERRUPTS();

		/*
		 * Sleep at least 1 second after any error.  A write error is likely
		 * to be repeated, and we don't want to be filling the error logs as
		 * fast as we can.
		 */
		pg_usleep(1000000L);

		/*
		 * Close all open files after any error.  This is helpful on Windows,
		 * where holding deleted files open causes various strange errors.
		 * It's not clear we need it elsewhere, but shouldn't hurt.
		 */
		smgrcloseall();
	}

	/* We can now handle ereport(ERROR) */
	PG_exception_stack = &local_sigjmp_buf;

	/*
	 * Unblock signals (they were blocked when the postmaster forked us)
	 */
	PG_SETMASK(&UnBlockSig);

	/*
	 * Loop forever
	 */
	for (;;)
	{
		long		udelay;

		/*
		 * Emergency bailout if postmaster has died.  This is to avoid the
		 * necessity for manual cleanup of all postmaster children.
		 */
		if (!PostmasterIsAlive(true))
			exit(1);

		/*
		 * Process any requests or signals received recently.
		 */
		if (got_SIGHUP)
		{
			got_SIGHUP = false;
			ProcessConfigFile(PGC_SIGHUP);
		}
		if (shutdown_requested)
		{
			/* Normal exit from the walwriter is here */
			proc_exit(0);		/* done */
		}

		/*
		 * Do what we're here for...
		 */
		XLogBackgroundFlush();

		/*
		 * Delay until time to do something more, but fall out of delay
		 * reasonably quickly if signaled.
		 */
		udelay = WalWriterDelay * 1000L;
		while (udelay > 999999L)
		{
			if (got_SIGHUP || shutdown_requested)
				break;
			pg_usleep(1000000L);
			udelay -= 1000000L;
		}
		if (!(got_SIGHUP || shutdown_requested))
			pg_usleep(udelay);
	}
}

/*
 * Main entry point for syslogger process
 * argc/argv parameters are valid only in EXEC_BACKEND case.
 */
NON_EXEC_STATIC void
SysLoggerMain(int argc, char *argv[])
{
	char	   *currentLogDir;
	char	   *currentLogFilename;
	int			currentLogRotationAge;

	IsUnderPostmaster = true;	/* we are a postmaster subprocess now */

	MyProcPid = getpid();		/* reset MyProcPid */

	/* Lose the postmaster's on-exit routines */
	on_exit_reset();

#ifdef EXEC_BACKEND
	syslogger_parseArgs(argc, argv);
#endif   /* EXEC_BACKEND */

	am_syslogger = true;

	init_ps_display("logger process", "", "");
	set_ps_display("");

	/*
	 * If we restarted, our stderr is already redirected into our own
	 * input pipe.	This is of course pretty useless, not to mention that
	 * it interferes with detecting pipe EOF.  Point stderr to /dev/null.
	 * This assumes that all interesting messages generated in the
	 * syslogger will come through elog.c and will be sent to
	 * write_syslogger_file.
	 */
	if (redirection_done)
	{
		int			fd = open(NULL_DEV, O_WRONLY);

		/*
		 * The closes might look redundant, but they are not: we want to
		 * be darn sure the pipe gets closed even if the open failed.  We
		 * can survive running with stderr pointing nowhere, but we can't
		 * afford to have extra pipe input descriptors hanging around.
		 */
		close(fileno(stdout));
		close(fileno(stderr));
		dup2(fd, fileno(stdout));
		dup2(fd, fileno(stderr));
		close(fd);
	}

	/*
	 * Also close our copy of the write end of the pipe.  This is needed
	 * to ensure we can detect pipe EOF correctly.	(But note that in the
	 * restart case, the postmaster already did this.)
	 */
#ifndef WIN32
	if (syslogPipe[1] >= 0)
		close(syslogPipe[1]);
	syslogPipe[1] = -1;
#else
	if (syslogPipe[1])
		CloseHandle(syslogPipe[1]);
	syslogPipe[1] = 0;
#endif

	/*
	 * Properly accept or ignore signals the postmaster might send us
	 *
	 * Note: we ignore all termination signals, and instead exit only when
	 * all upstream processes are gone, to ensure we don't miss any dying
	 * gasps of broken backends...
	 */

	pqsignal(SIGHUP, sigHupHandler);	/* set flag to read config file */
	pqsignal(SIGINT, SIG_IGN);
	pqsignal(SIGTERM, SIG_IGN);
	pqsignal(SIGQUIT, SIG_IGN);
	pqsignal(SIGALRM, SIG_IGN);
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, SIG_IGN);
	pqsignal(SIGUSR2, SIG_IGN);

	/*
	 * Reset some signals that are accepted by postmaster but not here
	 */
	pqsignal(SIGCHLD, SIG_DFL);
	pqsignal(SIGTTIN, SIG_DFL);
	pqsignal(SIGTTOU, SIG_DFL);
	pqsignal(SIGCONT, SIG_DFL);
	pqsignal(SIGWINCH, SIG_DFL);

	PG_SETMASK(&UnBlockSig);

#ifdef WIN32
	/* Fire up separate data transfer thread */
	InitializeCriticalSection(&sysfileSection);

	{
//.........这里部分代码省略.........

//.........这里部分代码省略.........
	on_exit_reset();

	/* Identify myself via ps */
	init_ps_display(serviceConfig->psTitle, "", "", "");

	if (serviceConfig->ServiceEarlyInit != NULL)
	{
		serviceConfig->ServiceEarlyInit();
	}
	else
	{
		SetProcessingMode(InitProcessing);
	}

	/*
	 * Set up signal handlers.	We operate on databases much like a regular
	 * backend, so we use the same signal handling.  See equivalent code in
	 * tcop/postgres.c.
	 *
	 * Currently, we don't pay attention to postgresql.conf changes that
	 * happen during a single daemon iteration, so we can ignore SIGHUP.
	 */
	pqsignal(SIGHUP, SIG_IGN);

	/*
	 * Presently, SIGINT will lead to autovacuum shutdown, because that's how
	 * we handle ereport(ERROR).  It could be improved however.
	 */
	pqsignal(SIGINT, StatementCancelHandler);
	pqsignal(SIGTERM, ServiceDie);
	pqsignal(SIGQUIT, ServiceQuickDie);
	pqsignal(SIGALRM, handle_sig_alarm);

	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
	/* We don't listen for async notifies */
	pqsignal(SIGUSR2, serviceConfig->ServiceRequestShutdown);
	pqsignal(SIGFPE, FloatExceptionHandler);
	pqsignal(SIGCHLD, SIG_DFL);

#ifdef SIGBUS
    pqsignal(SIGBUS, HandleCrash);
#endif
#ifdef SIGILL
    pqsignal(SIGILL, HandleCrash);
#endif
#ifdef SIGSEGV
    pqsignal(SIGSEGV, HandleCrash);
#endif


	/* Early initialization */
	BaseInit();

	if (serviceConfig->ServicePostgresInit != NULL)
	{
		serviceConfig->ServicePostgresInit();
	}

	SetProcessingMode(NormalProcessing);

	/*
	 * If an exception is encountered, processing resumes here.
	 *
	 * See notes in postgres.c about the design of this coding.
	 */
	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
	{
		/* Prevents interrupts while cleaning up */
		HOLD_INTERRUPTS();

		/* Report the error to the server log */
		EmitErrorReport();

		/*
		 * We can now go away.	Note that because we'll call InitProcess, a
		 * callback will be registered to do ProcKill, which will clean up
		 * necessary state.
		 */
		proc_exit(0);
	}

	/* We can now handle ereport(ERROR) */
	PG_exception_stack = &local_sigjmp_buf;

	PG_SETMASK(&UnBlockSig);

	/* set up a listener port and put it in shmem*/
	serviceCtrl->listenerPort = ServiceListenerSetup(serviceCtrl);

	if (serviceConfig->ServiceInit != NULL)
	{
		serviceConfig->ServiceInit(serviceCtrl->listenerPort);
	}

	/* listen loop */
	ServiceListenLoop(serviceCtrl);

	proc_exit(0);
}

//.........这里部分代码省略.........
		 * Now return to normal top-level context and clear ErrorContext for
		 * next time.
		 */
		MemoryContextSwitchTo(checkpointer_context);
		FlushErrorState();

		/* Flush any leaked data in the top-level context */
		MemoryContextResetAndDeleteChildren(checkpointer_context);

		/* Now we can allow interrupts again */
		RESUME_INTERRUPTS();

		/*
		 * Sleep at least 1 second after any error.  A write error is likely
		 * to be repeated, and we don't want to be filling the error logs as
		 * fast as we can.
		 */
		pg_usleep(1000000L);

		/*
		 * Close all open files after any error.  This is helpful on Windows,
		 * where holding deleted files open causes various strange errors.
		 * It's not clear we need it elsewhere, but shouldn't hurt.
		 */
		smgrcloseall();
	}

	/* We can now handle ereport(ERROR) */
	PG_exception_stack = &local_sigjmp_buf;

	/*
	 * Unblock signals (they were blocked when the postmaster forked us)
	 */
	PG_SETMASK(&UnBlockSig);

	/*
	 * Ensure all shared memory values are set correctly for the config. Doing
	 * this here ensures no race conditions from other concurrent updaters.
	 */
	UpdateSharedMemoryConfig();

	/*
	 * Advertise our latch that backends can use to wake us up while we're
	 * sleeping.
	 */
	ProcGlobal->checkpointerLatch = &MyProc->procLatch;

	/*
	 * Loop forever
	 */
	for (;;)
	{
		bool		do_checkpoint = false;
		int			flags = 0;
		pg_time_t	now;
		int			elapsed_secs;
		int			cur_timeout;
		int			rc;

		/* Clear any already-pending wakeups */
		ResetLatch(MyLatch);

		/*
		 * Process any requests or signals received recently.
		 */
		AbsorbFsyncRequests();

/**
 * This method is called after fork of the sweeper process. It sets up signal
 * handlers and does initialization that is required by a postgres backend.
 */
NON_EXEC_STATIC void
BackoffSweeperMain(int argc, char *argv[])
{
	sigjmp_buf	local_sigjmp_buf;

	IsUnderPostmaster = true;
	isSweeperProcess = true;

	/* Stay away from PMChildSlot */
	MyPMChildSlot = -1;

	/* reset MyProcPid */
	MyProcPid = getpid();

	/* Lose the postmaster's on-exit routines */
	on_exit_reset();

	/* Identify myself via ps */
	init_ps_display("sweeper process", "", "", "");

	SetProcessingMode(InitProcessing);

	/*
	 * Set up signal handlers.  We operate on databases much like a regular
	 * backend, so we use the same signal handling.  See equivalent code in
	 * tcop/postgres.c.
	 */
	pqsignal(SIGHUP, SIG_IGN);
	pqsignal(SIGINT, SIG_IGN);
	pqsignal(SIGALRM, SIG_IGN);
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, SIG_IGN);

	pqsignal(SIGTERM, die);
	pqsignal(SIGQUIT, quickdie);
	pqsignal(SIGUSR2, BackoffRequestShutdown);

	pqsignal(SIGFPE, FloatExceptionHandler);
	pqsignal(SIGCHLD, SIG_DFL);

	/*
	 * Copied from bgwriter
	 */
	CurrentResourceOwner = ResourceOwnerCreate(NULL, "Sweeper process");

	/* Early initialization */
	BaseInit();

	/* See InitPostgres()... */
	InitProcess();

	SetProcessingMode(NormalProcessing);

	/*
	 * If an exception is encountered, processing resumes here.
	 *
	 * See notes in postgres.c about the design of this coding.
	 */
	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
	{
		/* Prevents interrupts while cleaning up */
		HOLD_INTERRUPTS();

		/* Report the error to the server log */
		EmitErrorReport();

		/*
		 * We can now go away.  Note that because we'll call InitProcess, a
		 * callback will be registered to do ProcKill, which will clean up
		 * necessary state.
		 */
		proc_exit(0);
	}

	/* We can now handle ereport(ERROR) */
	PG_exception_stack = &local_sigjmp_buf;

	PG_SETMASK(&UnBlockSig);

	MyBackendId = InvalidBackendId;

	/* main loop */
	BackoffSweeperLoop();

	/* One iteration done, go away */
	proc_exit(0);
}

//.........这里部分代码省略.........
	 * processes do this.)
	 */
#ifdef HAVE_SETSID
	if (setsid() < 0)
		elog(FATAL, "setsid() failed: %m");
#endif

	/*
	 * Properly accept or ignore signals the postmaster might send us
	 *
	 * Note: we ignore all termination signals, and instead exit only when all
	 * upstream processes are gone, to ensure we don't miss any dying gasps of
	 * broken backends...
	 */

	pqsignal(SIGHUP, sigHupHandler);	/* set flag to read config file */
	pqsignal(SIGINT, SIG_IGN);
	pqsignal(SIGTERM, SIG_IGN);
	pqsignal(SIGQUIT, SIG_IGN);
	pqsignal(SIGALRM, SIG_IGN);
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, sigUsr1Handler);	/* request log rotation */
	pqsignal(SIGUSR2, SIG_IGN);

	/*
	 * Reset some signals that are accepted by postmaster but not here
	 */
	pqsignal(SIGCHLD, SIG_DFL);
	pqsignal(SIGTTIN, SIG_DFL);
	pqsignal(SIGTTOU, SIG_DFL);
	pqsignal(SIGCONT, SIG_DFL);
	pqsignal(SIGWINCH, SIG_DFL);

	PG_SETMASK(&UnBlockSig);

#ifdef WIN32
	/* Fire up separate data transfer thread */
	InitializeCriticalSection(&sysloggerSection);
	EnterCriticalSection(&sysloggerSection);

	threadHandle = (HANDLE) _beginthreadex(NULL, 0, pipeThread, NULL, 0, NULL);
	if (threadHandle == 0)
		elog(FATAL, "could not create syslogger data transfer thread: %m");
#endif   /* WIN32 */

	/* remember active logfile parameters */
	currentLogDir = pstrdup(Log_directory);
	currentLogFilename = pstrdup(Log_filename);
	currentLogRotationAge = Log_RotationAge;
	/* set next planned rotation time */
	set_next_rotation_time();

	/* main worker loop */
	for (;;)
	{
		bool		time_based_rotation = false;
		int			size_rotation_for = 0;

#ifndef WIN32
		int			bytesRead;
		int			rc;
		fd_set		rfds;
		struct timeval timeout;
#endif

		if (got_SIGHUP)

//.........这里部分代码省略.........
		/* Forget any pending QueryCancel or timeout request */
		disable_all_timeouts(false);
		QueryCancelPending = false; /* second to avoid race condition */

		/* Report the error to the server log */
		EmitErrorReport();

		/* Abort the current transaction in order to recover */
		AbortCurrentTransaction();

		/*
		 * Now return to normal top-level context and clear ErrorContext for
		 * next time.
		 */
		MemoryContextSwitchTo(ContQuerySchedulerMemCxt);
		FlushErrorState();

		/* Flush any leaked data in the top-level context */
		MemoryContextResetAndDeleteChildren(ContQuerySchedulerMemCxt);

		/* Now we can allow interrupts again */
		RESUME_INTERRUPTS();

		/*
		 * Sleep at least 1 second after any error.  We don't want to be
		 * filling the error logs as fast as we can.
		 */
		pg_usleep(1000000L);
	}
	/* We can now handle ereport(ERROR) */
	PG_exception_stack = &local_sigjmp_buf;

	/* must unblock signals before calling rebuild_database_list */
	PG_SETMASK(&UnBlockSig);

	ContQuerySchedulerShmem->scheduler_pid = MyProcPid;

	dbs = get_database_list();

	/* Loop forever */
	for (;;)
	{
		ListCell *lc;
		int rc;

		foreach(lc, dbs)
		{
			DatabaseEntry *db_entry = lfirst(lc);
			bool found;
			ContQueryProcGroup *grp = hash_search(ContQuerySchedulerShmem->proc_table, &db_entry->oid, HASH_ENTER, &found);

			/* If we don't have an entry for this dboid, initialize a new one and fire off bg procs */
			if (!found)
			{
				grp->db_oid = db_entry->oid;
				namestrcpy(&grp->db_name, NameStr(db_entry->name));

				start_group(grp);
			}
		}

		/* Allow sinval catchup interrupts while sleeping */
		EnableCatchupInterrupt();

		/*
		 * Wait until naptime expires or we get some type of signal (all the

void FileRepResetPeer_Main(void)
{
	/* BASIC PROCESS SETUP */

	FileRepReset_ConfigureSignals();

	/*
	 * If an exception is encountered, processing resumes here.
	 *
	 * See notes in postgres.c about the design of this coding and comments about how the error
	 * handling works.
	 */
	sigjmp_buf		local_sigjmp_buf;
	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
	{
		HOLD_INTERRUPTS();
		EmitErrorReport();
		proc_exit(EXIT_CODE_SHOULD_ENTER_FAULT);
	}
	/* We can now handle ereport(ERROR) */
	PG_exception_stack = &local_sigjmp_buf;
	PG_SETMASK(&UnBlockSig);


	/** NOW DO THE ACTUAL WORK */ 
	char messageFromPeer[MESSAGE_FROM_PEER_BUF_SIZE];
	char resetNumberFromPeer[MESSAGE_FROM_PEER_BUF_SIZE];
	char resetNumberThatIndicatesResetComplete[MESSAGE_FROM_PEER_BUF_SIZE];
	struct addrinfo *addrList = NULL;
	char portStr[100];

	PrimaryMirrorModeTransitionArguments args = primaryMirrorGetArgumentsFromLocalMemory();
	Assert(args.mode == PMModePrimarySegment || args.mode == PMModeMirrorSegment);

	snprintf(portStr, sizeof(portStr), "%d", args.peerPostmasterPort);
	if (! determineTargetHost(&addrList, args.peerAddress, portStr))
	{
		elog(WARNING, "during reset, unable to look up address for peer host to coordinate reset; "
				"will transition to fault state.");
		proc_exit(EXIT_CODE_SHOULD_ENTER_FAULT);
	}

	sendMessageToPeerAndExitIfProblem(addrList, "beginPostmasterReset", messageFromPeer,
		resetNumberThatIndicatesResetComplete);

	for ( ;; )
	{
		pg_usleep(10 * 1000L); /* 10 ms */
		sendMessageToPeerAndExitIfProblem(addrList, "getPostmasterResetStatus", messageFromPeer, resetNumberFromPeer );
		if (strequals(messageFromPeer, RESET_STATUS_IS_IN_RESET_PIVOT_POINT))
		{
			if (args.mode == PMModeMirrorSegment)
			{
				/**
				 * peer is in the reset pivot point, we can break out of our checking loop and
				 *   thus exit with a code telling the postmaster to begin the startup sequence again
				 *
				 * this is only done on the mirror as currently the mirror must execute the startup sequence
				 *   before the primary
				 */
				elog(DEBUG1, "peer reset: primary peer has reached reset point");
				break;
			}
		}
		else if (strequals(messageFromPeer, RESET_STATUS_IS_RUNNING))
		{
			/** it's running -- is it >= than the reset number that indicates reset complete one */
			if (strcmp( resetNumberFromPeer, resetNumberThatIndicatesResetComplete) >= 0)
			{
				/** yes, the reset is complete and so we can quit and do a restart */
				elog(DEBUG1, "peer reset: mirror peer reset is complete");
				break;
			}
		}
	}

	proc_exit(EXIT_CODE_SHOULD_RESTART_SHMEM_CLEANLY);
}