syslogger.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

#ifdef EXEC_BACKEND
	switch ((sysloggerPid = syslogger_forkexec()))
#else
	switch ((sysloggerPid = fork_process()))
#endif
	{
		case -1:
			ereport(LOG,
					(errmsg("could not fork system logger: %m")));
			return 0;

#ifndef EXEC_BACKEND
		case 0:
			/* in postmaster child ... */
			/* Close the postmaster's sockets */
			ClosePostmasterPorts(true);

			/* Drop our connection to postmaster's shared memory, as well */
			PGSharedMemoryDetach();

			/* do the work */
			SysLoggerMain(0, NULL);
			break;
#endif

		default:
			/* success, in postmaster */

			/* now we redirect stderr, if not done already */
			if (!redirection_done)
			{
#ifndef WIN32
				fflush(stdout);
				if (dup2(syslogPipe[1], fileno(stdout)) < 0)
					ereport(FATAL,
							(errcode_for_file_access(),
							 errmsg("could not redirect stdout: %m")));
				fflush(stderr);
				if (dup2(syslogPipe[1], fileno(stderr)) < 0)
					ereport(FATAL,
							(errcode_for_file_access(),
							 errmsg("could not redirect stderr: %m")));
				/* Now we are done with the write end of the pipe. */
				close(syslogPipe[1]);
				syslogPipe[1] = -1;
#else
				int			fd;

				fflush(stderr);
				fd = _open_osfhandle((long) syslogPipe[1],
									 _O_APPEND | _O_TEXT);
				if (dup2(fd, _fileno(stderr)) < 0)
					ereport(FATAL,
							(errcode_for_file_access(),
							 errmsg("could not redirect stderr: %m")));
				close(fd);
				/* Now we are done with the write end of the pipe. */
				CloseHandle(syslogPipe[1]);
				syslogPipe[1] = 0;
#endif
				redirection_done = true;
			}

			/* postmaster will never write the file; close it */
			fclose(syslogFile);
			syslogFile = NULL;
			return (int) sysloggerPid;
	}

	/* we should never reach here */
	return 0;
}


#ifdef EXEC_BACKEND

/*
 * syslogger_forkexec() -
 *
 * Format up the arglist for, then fork and exec, a syslogger process
 */
static pid_t
syslogger_forkexec(void)
{
	char	   *av[10];
	int			ac = 0,
				bufc = 0,
				i;
	char		numbuf[2][32];

	av[ac++] = "postgres";
	av[ac++] = "-forklog";
	av[ac++] = NULL;			/* filled in by postmaster_forkexec */

	/* static variables (those not passed by write_backend_variables) */
#ifndef WIN32
	if (syslogFile != NULL)
		snprintf(numbuf[bufc++], 32, "%d", fileno(syslogFile));
	else
		strcpy(numbuf[bufc++], "-1");
	snprintf(numbuf[bufc++], 32, "%d", (int) redirection_done);
#else							/* WIN32 */
	if (syslogFile != NULL)
		snprintf(numbuf[bufc++], 32, "%ld",
				 _get_osfhandle(_fileno(syslogFile)));
	else
		strcpy(numbuf[bufc++], "0");
	snprintf(numbuf[bufc++], 32, "%d", (int) redirection_done);
#endif   /* WIN32 */

	/* Add to the arg list */
	Assert(bufc <= lengthof(numbuf));
	for (i = 0; i < bufc; i++)
		av[ac++] = numbuf[i];

	av[ac] = NULL;
	Assert(ac < lengthof(av));

	return postmaster_forkexec(ac, av);
}

/*
 * syslogger_parseArgs() -
 *
 * Extract data from the arglist for exec'ed syslogger process
 */
static void
syslogger_parseArgs(int argc, char *argv[])
{
	int			fd;

	Assert(argc == 5);
	argv += 3;

#ifndef WIN32
	fd = atoi(*argv++);
	if (fd != -1)
	{
		syslogFile = fdopen(fd, "a");
		setvbuf(syslogFile, NULL, LBF_MODE, 0);
	}
	redirection_done = (bool) atoi(*argv++);
#else							/* WIN32 */
	fd = atoi(*argv++);
	if (fd != 0)
	{
		fd = _open_osfhandle(fd, _O_APPEND);
		if (fd > 0)
		{
			syslogFile = fdopen(fd, "a");
			setvbuf(syslogFile, NULL, LBF_MODE, 0);
		}
	}
	redirection_done = (bool) atoi(*argv++);
#endif   /* WIN32 */
}
#endif   /* EXEC_BACKEND */


/* --------------------------------
 *		logfile routines
 * --------------------------------
 */

/*
 * Write text to the currently open logfile
 *
 * This is exported so that elog.c can call it when am_syslogger is true.
 * This allows the syslogger process to record elog messages of its own,
 * even though its stderr does not point at the syslog pipe.
 */
void
write_syslogger_file(const char *buffer, int count)
{
#ifdef WIN32

	/*
	 * On Windows we need to do our own newline-to-CRLF translation.
	 */
	char		convbuf[256];
	char	   *p;
	int			n;

	p = convbuf;
	n = 0;
	while (count-- > 0)
	{
		if (*buffer == '\n')
		{
			*p++ = '\r';
			n++;
		}
		*p++ = *buffer++;
		n++;
		if (n >= sizeof(convbuf) - 1)
		{
			write_syslogger_file_binary(convbuf, n);
			p = convbuf;
			n = 0;
		}
	}
	if (n > 0)
		write_syslogger_file_binary(convbuf, n);
#else							/* !WIN32 */
	write_syslogger_file_binary(buffer, count);
#endif
}

/*
 * Write binary data to the currently open logfile
 *
 * On Windows the data arriving in the pipe already has CR/LF newlines,
 * so we must send it to the file without further translation.
 */
static void
write_syslogger_file_binary(const char *buffer, int count)
{
	int			rc;

#ifndef WIN32
	rc = fwrite(buffer, 1, count, syslogFile);
#else
	EnterCriticalSection(&sysfileSection);
	rc = fwrite(buffer, 1, count, syslogFile);
	LeaveCriticalSection(&sysfileSection);
#endif

	/* can't use ereport here because of possible recursion */
	if (rc != count)
		write_stderr("could not write to log file: %s\n", strerror(errno));
}

#ifdef WIN32

/*
 * Worker thread to transfer data from the pipe to the current logfile.
 *
 * We need this because on Windows, WaitForSingleObject does not work on
 * unnamed pipes: it always reports "signaled", so the blocking ReadFile won't
 * allow for SIGHUP; and select is for sockets only.
 */
static unsigned int __stdcall
pipeThread(void *arg)
{
	DWORD		bytesRead;
	char		logbuffer[1024];

	for (;;)
	{
		if (!ReadFile(syslogPipe[0], logbuffer, sizeof(logbuffer),
					  &bytesRead, 0))
		{
			DWORD		error = GetLastError();

			if (error == ERROR_HANDLE_EOF ||
				error == ERROR_BROKEN_PIPE)
				break;
			_dosmaperr(error);
			ereport(LOG,
					(errcode_for_file_access(),
					 errmsg("could not read from logger pipe: %m")));
		}
		else if (bytesRead > 0)
			write_syslogger_file_binary(logbuffer, bytesRead);
	}

	/* We exit the above loop only upon detecting pipe EOF */
	pipe_eof_seen = true;
	_endthread();
	return 0;
}
#endif   /* WIN32 */

/*
 * perform logfile rotation
 */
static void
logfile_rotate(bool time_based_rotation)
{
	char	   *filename;
	FILE	   *fh;

	rotation_requested = false;

	/*
	 * When doing a time-based rotation, invent the new logfile name based on
	 * the planned rotation time, not current time, to avoid "slippage" in the
	 * file name when we don't do the rotation immediately.
	 */
	if (time_based_rotation)
		filename = logfile_getname(next_rotation_time);
	else
		filename = logfile_getname(time(NULL));

	/*
	 * Decide whether to overwrite or append.  We can overwrite if (a)
	 * Log_truncate_on_rotation is set, (b) the rotation was triggered by
	 * elapsed time and not something else, and (c) the computed file name is
	 * different from what we were previously logging into.
	 *
	 * Note: during the first rotation after forking off from the postmaster,
	 * last_file_name will be NULL.  (We don't bother to set it in the
	 * postmaster because it ain't gonna work in the EXEC_BACKEND case.) So we
	 * will always append in that situation, even though truncating would
	 * usually be safe.
	 */
	if (Log_truncate_on_rotation && time_based_rotation &&
		last_file_name != NULL && strcmp(filename, last_file_name) != 0)
		fh = fopen(filename, "w");
	else
		fh = fopen(filename, "a");

	if (!fh)
	{
		int			saveerrno = errno;

		ereport(LOG,
				(errcode_for_file_access(),
				 errmsg("could not open new log file \"%s\": %m",
						filename)));

		/*
		 * ENFILE/EMFILE are not too surprising on a busy system; just keep
		 * using the old file till we manage to get a new one. Otherwise,
		 * assume something's wrong with Log_directory and stop trying to
		 * create files.
		 */
		if (saveerrno != ENFILE && saveerrno != EMFILE)
		{
			ereport(LOG,
					(errmsg("disabling automatic rotation (use SIGHUP to reenable)")));
			Log_RotationAge = 0;
			Log_RotationSize = 0;
		}
		pfree(filename);
		return;
	}

	setvbuf(fh, NULL, LBF_MODE, 0);

	/* On Windows, need to interlock against data-transfer thread */
#ifdef WIN32
	EnterCriticalSection(&sysfileSection);
#endif
	fclose(syslogFile);
	syslogFile = fh;
#ifdef WIN32
	LeaveCriticalSection(&sysfileSection);
#endif

	set_next_rotation_time();

	/* instead of pfree'ing filename, remember it for next time */
	if (last_file_name != NULL)
		pfree(last_file_name);
	last_file_name = filename;
}


/*
 * construct logfile name using timestamp information
 *
 * Result is palloc'd.
 */
static char *
logfile_getname(pg_time_t timestamp)
{
	char	   *filename;
	int			len;
	struct pg_tm *tm;

	filename = palloc(MAXPGPATH);

	snprintf(filename, MAXPGPATH, "%s/", Log_directory);

	len = strlen(filename);

	if (strchr(Log_filename, '%'))
	{
		/* treat it as a strftime pattern */
		tm = pg_localtime(&timestamp, global_timezone);
		pg_strftime(filename + len, MAXPGPATH - len, Log_filename, tm);
	}
	else
	{
		/* no strftime escapes, so append timestamp to new filename */
		snprintf(filename + len, MAXPGPATH - len, "%s.%lu",
				 Log_filename, (unsigned long) timestamp);
	}

	return filename;
}

/*
 * Determine the next planned rotation time, and store in next_rotation_time.
 */
static void
set_next_rotation_time(void)
{
	pg_time_t	now;
	struct pg_tm *tm;
	int			rotinterval;

	/* nothing to do if time-based rotation is disabled */
	if (Log_RotationAge <= 0)
		return;

	/*
	 * The requirements here are to choose the next time > now that is a
	 * "multiple" of the log rotation interval.  "Multiple" can be interpreted
	 * fairly loosely.	In this version we align to local time rather than
	 * GMT.
	 */
	rotinterval = Log_RotationAge * SECS_PER_MINUTE;	/* convert to seconds */
	now = time(NULL);
	tm = pg_localtime(&now, global_timezone);
	now += tm->tm_gmtoff;
	now -= now % rotinterval;
	now += rotinterval;
	now -= tm->tm_gmtoff;
	next_rotation_time = now;
}

/* --------------------------------
 *		signal handler routines
 * --------------------------------
 */

/* SIGHUP: set flag to reload config file */
static void
sigHupHandler(SIGNAL_ARGS)
{
	got_SIGHUP = true;
}

/* SIGUSR1: set flag to rotate logfile */
static void
sigUsr1Handler(SIGNAL_ARGS)
{
	rotation_requested = true;
}