text: /*-------------------------------------------------------------------------
   *
   * syslogger.c
   *
   * The system logger (syslogger) appeared in Postgres 8.0. It catches all
   * stderr output from the postmaster, backends, and other subprocesses
   * by redirecting to a pipe, and writes it to a set of logfiles.
   * It's possible to have size and age limits for the logfile configured
   * in postgresql.conf. If these limits are reached or passed, the
   * current logfile is closed and a new one is created (rotated).
   * The logfiles are stored in a subdirectory (configurable in
   * postgresql.conf), using a user-selectable naming scheme.
   *
   * Author: Andreas Pflug <pgadmin@pse-consulting.de>
   *
   * Copyright (c) 2004-2021, PostgreSQL Global Development Group
   *
   *
   * IDENTIFICATION
   *	  src/backend/postmaster/syslogger.c
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include <fcntl.h>
  #include <limits.h>
  #include <signal.h>
  #include <time.h>
  #include <unistd.h>
  #include <sys/stat.h>
  #include <sys/time.h>
  
  #include "common/file_perm.h"
  #include "lib/stringinfo.h"
  #include "libpq/pqsignal.h"
  #include "miscadmin.h"
  #include "nodes/pg_list.h"
  #include "pgstat.h"
  #include "pgtime.h"
  #include "port/pg_bitutils.h"
  #include "postmaster/fork_process.h"
  #include "postmaster/interrupt.h"
  #include "postmaster/postmaster.h"
  #include "postmaster/syslogger.h"
  #include "storage/dsm.h"
  #include "storage/fd.h"
  #include "storage/ipc.h"
  #include "storage/latch.h"
  #include "storage/pg_shmem.h"
  #include "tcop/tcopprot.h"
  #include "utils/guc.h"
  #include "utils/ps_status.h"
  #include "utils/timestamp.h"
  
  /*
   * We read() into a temp buffer twice as big as a chunk, so that any fragment
   * left after processing can be moved down to the front and we'll still have
   * room to read a full chunk.
   */
  #define READ_BUF_SIZE (2 * PIPE_CHUNK_SIZE)
  
  /* Log rotation signal file path, relative to $PGDATA */
  #define LOGROTATE_SIGNAL_FILE	"logrotate"
  
  
  /*
   * GUC parameters.  Logging_collector cannot be changed after postmaster
   * start, but the rest can change at SIGHUP.
   */
  bool		Logging_collector = false;
  int			Log_RotationAge = HOURS_PER_DAY * MINS_PER_HOUR;
  int			Log_RotationSize = 10 * 1024;
  char	   *Log_directory = NULL;
  char	   *Log_filename = NULL;
  bool		Log_truncate_on_rotation = false;
  int			Log_file_mode = S_IRUSR | S_IWUSR;
  
  extern bool redirection_done;
  
  /*
   * Private state
   */
  static pg_time_t next_rotation_time;
  static bool pipe_eof_seen = false;
  static bool rotation_disabled = false;
  static FILE *syslogFile = NULL;
  static FILE *csvlogFile = NULL;
  NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
  static char *last_sys_file_name = NULL;
  static char *last_csv_file_name = NULL;
  
  /*
   * Buffers for saving partial messages from different backends.
   *
   * Keep NBUFFER_LISTS lists of these, with the entry for a given source pid
   * being in the list numbered (pid % NBUFFER_LISTS), so as to cut down on
   * the number of entries we have to examine for any one incoming message.
   * There must never be more than one entry for the same source pid.
   *
   * An inactive buffer is not removed from its list, just held for re-use.
   * An inactive buffer has pid == 0 and undefined contents of data.
   */
  typedef struct
  {
  	int32		pid;			/* PID of source process */
  	StringInfoData data;		/* accumulated data, as a StringInfo */
  } save_buffer;
  
  #define NBUFFER_LISTS 256
  static List *buffer_lists[NBUFFER_LISTS];
  
  /* These must be exported for EXEC_BACKEND case ... annoying */
  #ifndef WIN32
  int			syslogPipe[2] = {-1, -1};
  #else
  HANDLE		syslogPipe[2] = {0, 0};
  #endif
  
  #ifdef WIN32
  static HANDLE threadHandle = 0;
  static CRITICAL_SECTION sysloggerSection;
  #endif
  
  /*
   * Flags set by interrupt handlers for later service in the main loop.
   */
  static volatile sig_atomic_t rotation_requested = false;
  
  
  /* Local subroutines */
  #ifdef EXEC_BACKEND
  static int	syslogger_fdget(FILE *file);
  static FILE *syslogger_fdopen(int fd);
  static pid_t syslogger_forkexec(void);
  static void syslogger_parseArgs(int argc, char *argv[]);
  #endif
  NON_EXEC_STATIC void SysLoggerMain(int argc, char *argv[]) pg_attribute_noreturn();
  static void process_pipe_input(char *logbuffer, int *bytes_in_logbuffer);
  static void flush_pipe_input(char *logbuffer, int *bytes_in_logbuffer);
  static FILE *logfile_open(const char *filename, const char *mode,
  						  bool allow_errors);
  
  #ifdef WIN32
  static unsigned int __stdcall pipeThread(void *arg);
  #endif
  static void logfile_rotate(bool time_based_rotation, int size_rotation_for);
  static bool logfile_rotate_dest(bool time_based_rotation,
  								int size_rotation_for, pg_time_t fntime,
  								int target_dest, char **last_file_name,
  								FILE **logFile);
  static char *logfile_getname(pg_time_t timestamp, const char *suffix);
  static void set_next_rotation_time(void);
  static void sigUsr1Handler(SIGNAL_ARGS);
  static void update_metainfo_datafile(void);
  
  
  /*
   * 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[])
  {
  #ifndef WIN32
  	char		logbuffer[READ_BUF_SIZE];
  	int			bytes_in_logbuffer = 0;
  #endif
  	char	   *currentLogDir;
  	char	   *currentLogFilename;
  	int			currentLogRotationAge;
  	pg_time_t	now;
  	WaitEventSet *wes;
  
  	now = MyStartTime;
  
  #ifdef EXEC_BACKEND
  	syslogger_parseArgs(argc, argv);
  #endif							/* EXEC_BACKEND */
  
  	MyBackendType = B_LOGGER;
  	init_ps_display(NULL);
  
  	/*
  	 * 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(DEVNULL, O_WRONLY, 0);
  
  		/*
  		 * 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.
  		 *
  		 * As we're just trying to reset these to go to DEVNULL, there's not
  		 * much point in checking for failure from the close/dup2 calls here,
  		 * if they fail then presumably the file descriptors are closed and
  		 * any writes will go into the bitbucket anyway.
  		 */
  		close(fileno(stdout));
  		close(fileno(stderr));
  		if (fd != -1)
  		{
  			(void) dup2(fd, fileno(stdout));
  			(void) dup2(fd, fileno(stderr));
  			close(fd);
  		}
  	}
  
  	/*
  	 * Syslogger's own stderr can't be the syslogPipe, so set it back to text
  	 * mode if we didn't just close it. (It was set to binary in
  	 * SubPostmasterMain).
  	 */
  #ifdef WIN32
  	else
  		_setmode(_fileno(stderr), _O_TEXT);
  #endif
  
  	/*
  	 * 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, SignalHandlerForConfigReload); /* 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);
  
  	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 logfiles' name(s).  We recompute 'em 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_sys_file_name = logfile_getname(first_syslogger_file_time, NULL);
  	if (csvlogFile != NULL)
  		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
  
  	/* remember active logfile parameters */
  	currentLogDir = pstrdup(Log_directory);
  	currentLogFilename = pstrdup(Log_filename);
  	currentLogRotationAge = Log_RotationAge;
  	/* set next planned rotation time */
  	set_next_rotation_time();
  	update_metainfo_datafile();
  
  	/*
  	 * Reset whereToSendOutput, as the postmaster will do (but hasn't yet, at
  	 * the point where we forked).  This prevents duplicate output of messages
  	 * from syslogger itself.
  	 */
  	whereToSendOutput = DestNone;
  
  	/*
  	 * Set up a reusable WaitEventSet object we'll use to wait for our latch,
  	 * and (except on Windows) our socket.
  	 *
  	 * Unlike all other postmaster child processes, we'll ignore postmaster
  	 * death because we want to collect final log output from all backends and
  	 * then exit last.  We'll do that by running until we see EOF on the
  	 * syslog pipe, which implies that all other backends have exited
  	 * (including the postmaster).
  	 */
  	wes = CreateWaitEventSet(CurrentMemoryContext, 2);
  	AddWaitEventToSet(wes, WL_LATCH_SET, PGINVALID_SOCKET, MyLatch, NULL);
  #ifndef WIN32
  	AddWaitEventToSet(wes, WL_SOCKET_READABLE, syslogPipe[0], NULL, NULL);
  #endif
  
  	/* main worker loop */
  	for (;;)
  	{
  		bool		time_based_rotation = false;
  		int			size_rotation_for = 0;
  		long		cur_timeout;
  		WaitEvent	event;
  
  #ifndef WIN32
  		int			rc;
  #endif
  
  		/* Clear any already-pending wakeups */
  		ResetLatch(MyLatch);
  
  		/*
  		 * Process any requests or signals received recently.
  		 */
  		if (ConfigReloadPending)
  		{
  			ConfigReloadPending = false;
  			ProcessConfigFile(PGC_SIGHUP);
  
  			/*
  			 * Check if the log directory or filename pattern changed in
  			 * postgresql.conf. If so, force rotation to make sure we're
  			 * writing the logfiles in the right place.
  			 */
  			if (strcmp(Log_directory, currentLogDir) != 0)
  			{
  				pfree(currentLogDir);
  				currentLogDir = pstrdup(Log_directory);
  				rotation_requested = true;
  
  				/*
  				 * Also, create new directory if not present; ignore errors
  				 */
  				(void) MakePGDirectory(Log_directory);
  			}
  			if (strcmp(Log_filename, currentLogFilename) != 0)
  			{
  				pfree(currentLogFilename);
  				currentLogFilename = pstrdup(Log_filename);
  				rotation_requested = true;
  			}
  
  			/*
  			 * Force a rotation if CSVLOG output was just turned on or off and
  			 * we need to open or close csvlogFile accordingly.
  			 */
  			if (((Log_destination & LOG_DESTINATION_CSVLOG) != 0) !=
  				(csvlogFile != NULL))
  				rotation_requested = true;
  
  			/*
  			 * If rotation time parameter changed, reset next rotation time,
  			 * but don't immediately force a rotation.
  			 */
  			if (currentLogRotationAge != Log_RotationAge)
  			{
  				currentLogRotationAge = Log_RotationAge;
  				set_next_rotation_time();
  			}
  
  			/*
  			 * If we had a rotation-disabling failure, re-enable rotation
  			 * attempts after SIGHUP, and force one immediately.
  			 */
  			if (rotation_disabled)
  			{
  				rotation_disabled = false;
  				rotation_requested = true;
  			}
  
  			/*
  			 * Force rewriting last log filename when reloading configuration.
  			 * Even if rotation_requested is false, log_destination may have
  			 * been changed and we don't want to wait the next file rotation.
  			 */
  			update_metainfo_datafile();
  		}
  
  		if (Log_RotationAge > 0 && !rotation_disabled)
  		{
  			/* Do a logfile rotation if it's time */
  			now = (pg_time_t) time(NULL);
  			if (now >= next_rotation_time)
  				rotation_requested = time_based_rotation = true;
  		}
  
  		if (!rotation_requested && Log_RotationSize > 0 && !rotation_disabled)
  		{
  			/* Do a rotation if file is too big */
  			if (ftell(syslogFile) >= Log_RotationSize * 1024L)
  			{
  				rotation_requested = true;
  				size_rotation_for |= LOG_DESTINATION_STDERR;
  			}
  			if (csvlogFile != NULL &&
  				ftell(csvlogFile) >= Log_RotationSize * 1024L)
  			{
  				rotation_requested = true;
  				size_rotation_for |= LOG_DESTINATION_CSVLOG;
  			}
  		}
  
  		if (rotation_requested)
  		{
  			/*
  			 * Force rotation when both values are zero. It means the request
  			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
  			 */
  			if (!time_based_rotation && size_rotation_for == 0)
  				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
  			logfile_rotate(time_based_rotation, size_rotation_for);
  		}
  
  		/*
  		 * Calculate time till next time-based rotation, so that we don't
  		 * sleep longer than that.  We assume the value of "now" obtained
  		 * above is still close enough.  Note we can't make this calculation
  		 * until after calling logfile_rotate(), since it will advance
  		 * next_rotation_time.
  		 *
  		 * Also note that we need to beware of overflow in calculation of the
  		 * timeout: with large settings of Log_RotationAge, next_rotation_time
  		 * could be more than INT_MAX msec in the future.  In that case we'll
  		 * wait no more than INT_MAX msec, and try again.
  		 */
  		if (Log_RotationAge > 0 && !rotation_disabled)
  		{
  			pg_time_t	delay;
  
  			delay = next_rotation_time - now;
  			if (delay > 0)
  			{
  				if (delay > INT_MAX / 1000)
  					delay = INT_MAX / 1000;
  				cur_timeout = delay * 1000L;	/* msec */
  			}
  			else
  				cur_timeout = 0;
  		}
  		else
  			cur_timeout = -1L;
  
  		/*
  		 * Sleep until there's something to do
  		 */
  #ifndef WIN32
  		rc = WaitEventSetWait(wes, cur_timeout, &event, 1,
  							  WAIT_EVENT_SYSLOGGER_MAIN);
  
  		if (rc == 1 && event.events == WL_SOCKET_READABLE)
  		{
  			int			bytesRead;
  
  			bytesRead = read(syslogPipe[0],
  							 logbuffer + bytes_in_logbuffer,
  							 sizeof(logbuffer) - bytes_in_logbuffer);
  			if (bytesRead < 0)
  			{
  				if (errno != EINTR)
  					ereport(LOG,
  							(errcode_for_socket_access(),
  							 errmsg("could not read from logger pipe: %m")));
  			}
  			else if (bytesRead > 0)
  			{
  				bytes_in_logbuffer += bytesRead;
  				process_pipe_input(logbuffer, &bytes_in_logbuffer);
  				continue;
  			}
  			else
  			{
  				/*
  				 * Zero bytes read when select() is saying read-ready means
  				 * EOF on the pipe: that is, there are no longer any processes
  				 * with the pipe write end open.  Therefore, the postmaster
  				 * and all backends are shut down, and we are done.
  				 */
  				pipe_eof_seen = true;
  
  				/* if there's any data left then force it out now */
  				flush_pipe_input(logbuffer, &bytes_in_logbuffer);
  			}
  		}
  #else							/* WIN32 */
  
  		/*
  		 * On Windows we leave it to a separate thread to transfer data and
  		 * detect pipe EOF.  The main thread just wakes up to handle SIGHUP
  		 * and rotation conditions.
  		 *
  		 * Server code isn't generally thread-safe, so we ensure that only one
  		 * of the threads is active at a time by entering the critical section
  		 * whenever we're not sleeping.
  		 */
  		LeaveCriticalSection(&sysloggerSection);
  
  		(void) WaitEventSetWait(wes, cur_timeout, &event, 1,
  								WAIT_EVENT_SYSLOGGER_MAIN);
  
  		EnterCriticalSection(&sysloggerSection);
  #endif							/* WIN32 */
  
  		if (pipe_eof_seen)
  		{
  			/*
  			 * seeing this message on the real stderr is annoying - so we make
  			 * it DEBUG1 to suppress in normal use.
  			 */
  			ereport(DEBUG1,
  					(errmsg_internal("logger shutting down")));
  
  			/*
  			 * Normal exit from the syslogger is here.  Note that we
  			 * deliberately do not close syslogFile before exiting; this is to
  			 * allow for the possibility of elog messages being generated
  			 * inside proc_exit.  Regular exit() will take care of flushing
  			 * and closing stdio channels.
  			 */
  			proc_exit(0);
  		}
  	}
  }
  
  /*
   * Postmaster subroutine to start a syslogger subprocess.
   */
  int
  SysLogger_Start(void)
  {
  	pid_t		sysloggerPid;
  	char	   *filename;
  
  	if (!Logging_collector)
  		return 0;
  
  	/*
  	 * If first time through, create the pipe which will receive stderr
  	 * output.
  	 *
  	 * If the syslogger crashes and needs to be restarted, we continue to use
  	 * the same pipe (indeed must do so, since extant backends will be writing
  	 * into that pipe).
  	 *
  	 * This means the postmaster must continue to hold the read end of the
  	 * pipe open, so we can pass it down to the reincarnated syslogger. This
  	 * is a bit klugy but we have little choice.
  	 *
  	 * Also note that we don't bother counting the pipe FDs by calling
  	 * Reserve/ReleaseExternalFD.  There's no real need to account for them
  	 * accurately in the postmaster or syslogger process, and both ends of the
  	 * pipe will wind up closed in all other postmaster children.
  	 */
  #ifndef WIN32
  	if (syslogPipe[0] < 0)
  	{
  		if (pipe(syslogPipe) < 0)
  			ereport(FATAL,
  					(errcode_for_socket_access(),
  					 errmsg("could not create pipe for syslog: %m")));
  	}
  #else
  	if (!syslogPipe[0])
  	{
  		SECURITY_ATTRIBUTES sa;
  
  		memset(&sa, 0, sizeof(SECURITY_ATTRIBUTES));
  		sa.nLength = sizeof(SECURITY_ATTRIBUTES);
  		sa.bInheritHandle = TRUE;
  
  		if (!CreatePipe(&syslogPipe[0], &syslogPipe[1], &sa, 32768))
  			ereport(FATAL,
  					(errcode_for_file_access(),
  					 errmsg("could not create pipe for syslog: %m")));
  	}
  #endif
  
  	/*
  	 * Create log directory if not present; ignore errors
  	 */
  	(void) MakePGDirectory(Log_directory);
  
  	/*
  	 * The initial logfile is created right in the postmaster, to verify that
  	 * the Log_directory is writable.  We save the reference time so that the
  	 * syslogger child process can recompute this file name.
  	 *
  	 * It might look a bit strange to re-do this during a syslogger restart,
  	 * but we must do so since the postmaster closed syslogFile after the
  	 * previous fork (and remembering that old file wouldn't be right anyway).
  	 * Note we always append here, we won't overwrite any existing file.  This
  	 * is consistent with the normal rules, because by definition this is not
  	 * a time-based rotation.
  	 */
  	first_syslogger_file_time = time(NULL);
  
  	filename = logfile_getname(first_syslogger_file_time, NULL);
  
  	syslogFile = logfile_open(filename, "a", false);
  
  	pfree(filename);
  
  	/*
  	 * Likewise for the initial CSV log file, if that's enabled.  (Note that
  	 * we open syslogFile even when only CSV output is nominally enabled,
  	 * since some code paths will write to syslogFile anyway.)
  	 */
  	if (Log_destination & LOG_DESTINATION_CSVLOG)
  	{
  		filename = logfile_getname(first_syslogger_file_time, ".csv");
  
  		csvlogFile = logfile_open(filename, "a", false);
  
  		pfree(filename);
  	}
  
  #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 ... */
  			InitPostmasterChild();
  
  			/* Close the postmaster's sockets */
  			ClosePostmasterPorts(true);
  
  			/* Drop our connection to postmaster's shared memory, as well */
  			dsm_detach_all();
  			PGSharedMemoryDetach();
  
  			/* do the work */
  			SysLoggerMain(0, NULL);
  			break;
  #endif
  
  		default:
  			/* success, in postmaster */
  
  			/* now we redirect stderr, if not done already */
  			if (!redirection_done)
  			{
  #ifdef WIN32
  				int			fd;
  #endif
  
  				/*
  				 * Leave a breadcrumb trail when redirecting, in case the user
  				 * forgets that redirection is active and looks only at the
  				 * original stderr target file.
  				 */
  				ereport(LOG,
  						(errmsg("redirecting log output to logging collector process"),
  						 errhint("Future log output will appear in directory \"%s\".",
  								 Log_directory)));
  
  #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
  
  				/*
  				 * open the pipe in binary mode and make sure stderr is binary
  				 * after it's been dup'ed into, to avoid disturbing the pipe
  				 * chunking protocol.
  				 */
  				fflush(stderr);
  				fd = _open_osfhandle((intptr_t) syslogPipe[1],
  									 _O_APPEND | _O_BINARY);
  				if (dup2(fd, _fileno(stderr)) < 0)
  					ereport(FATAL,
  							(errcode_for_file_access(),
  							 errmsg("could not redirect stderr: %m")));
  				close(fd);
  				_setmode(_fileno(stderr), _O_BINARY);
  
  				/*
  				 * Now we are done with the write end of the pipe.
  				 * CloseHandle() must not be called because the preceding
  				 * close() closes the underlying handle.
  				 */
  				syslogPipe[1] = 0;
  #endif
  				redirection_done = true;
  			}
  
  			/* postmaster will never write the file(s); close 'em */
  			fclose(syslogFile);
  			syslogFile = NULL;
  			if (csvlogFile != NULL)
  			{
  				fclose(csvlogFile);
  				csvlogFile = NULL;
  			}
  			return (int) sysloggerPid;
  	}
  
  	/* we should never reach here */
  	return 0;
  }
  
  
  #ifdef EXEC_BACKEND
  
  /*
   * syslogger_fdget() -
   *
   * Utility wrapper to grab the file descriptor of an opened error output
   * file.  Used when building the command to fork the logging collector.
   */
  static int
  syslogger_fdget(FILE *file)
  {
  #ifndef WIN32
  	if (file != NULL)
  		return fileno(file);
  	else
  		return -1;
  #else
  	if (file != NULL)
  		return (int) _get_osfhandle(_fileno(file));
  	else
  		return 0;
  #endif							/* WIN32 */
  }
  
  /*
   * syslogger_fdopen() -
   *
   * Utility wrapper to re-open an error output file, using the given file
   * descriptor.  Used when parsing arguments in a forked logging collector.
   */
  static FILE *
  syslogger_fdopen(int fd)
  {
  	FILE	   *file = NULL;
  
  #ifndef WIN32
  	if (fd != -1)
  	{
  		file = fdopen(fd, "a");
  		setvbuf(file, NULL, PG_IOLBF, 0);
  	}
  #else							/* WIN32 */
  	if (fd != 0)
  	{
  		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
  		if (fd > 0)
  		{
  			file = fdopen(fd, "a");
  			setvbuf(file, NULL, PG_IOLBF, 0);
  		}
  	}
  #endif							/* WIN32 */
  
  	return file;
  }
  
  /*
   * 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;
  	char		filenobuf[32];
  	char		csvfilenobuf[32];
  
  	av[ac++] = "postgres";
  	av[ac++] = "--forklog";
  	av[ac++] = NULL;			/* filled in by postmaster_forkexec */
  
  	/* static variables (those not passed by write_backend_variables) */
  	snprintf(filenobuf, sizeof(filenobuf), "%d",
  			 syslogger_fdget(syslogFile));
  	av[ac++] = filenobuf;
  	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
  			 syslogger_fdget(csvlogFile));
  	av[ac++] = csvfilenobuf;
  
  	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;
  
  	/*
  	 * Re-open the error output files that were opened by SysLogger_Start().
  	 *
  	 * We expect this will always succeed, which is too optimistic, but if it
  	 * fails there's not a lot we can do to report the problem anyway.  As
  	 * coded, we'll just crash on a null pointer dereference after failure...
  	 */
  	fd = atoi(*argv++);
  	syslogFile = syslogger_fdopen(fd);
  	fd = atoi(*argv++);
  	csvlogFile = syslogger_fdopen(fd);
  }
  #endif							/* EXEC_BACKEND */
  
  
  /* --------------------------------
   *		pipe protocol handling
   * --------------------------------
   */
  
  /*
   * Process data received through the syslogger pipe.
   *
   * This routine interprets the log pipe protocol which sends log messages as
   * (hopefully atomic) chunks - such chunks are detected and reassembled here.
   *
   * The protocol has a header that starts with two nul bytes, then has a 16 bit
   * length, the pid of the sending process, and a flag to indicate if it is
   * the last chunk in a message. Incomplete chunks are saved until we read some
   * more, and non-final chunks are accumulated until we get the final chunk.
   *
   * All of this is to avoid 2 problems:
   * . partial messages being written to logfiles (messes rotation), and
   * . messages from different backends being interleaved (messages garbled).
   *
   * Any non-protocol messages are written out directly. These should only come
   * from non-PostgreSQL sources, however (e.g. third party libraries writing to
   * stderr).
   *
   * logbuffer is the data input buffer, and *bytes_in_logbuffer is the number
   * of bytes present.  On exit, any not-yet-eaten data is left-justified in
   * logbuffer, and *bytes_in_logbuffer is updated.
   */
  static void
  process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
  {
  	char	   *cursor = logbuffer;
  	int			count = *bytes_in_logbuffer;
  	int			dest = LOG_DESTINATION_STDERR;
  
  	/* While we have enough for a header, process data... */
  	while (count >= (int) (offsetof(PipeProtoHeader, data) + 1))
  	{
  		PipeProtoHeader p;
  		int			chunklen;
  		bits8		dest_flags;
  
  		/* Do we have a valid header? */
  		memcpy(&p, cursor, offsetof(PipeProtoHeader, data));
  		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG);
  		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
  			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
  			p.pid != 0 &&
  			pg_popcount((char *) &dest_flags, 1) == 1)
  		{
  			List	   *buffer_list;
  			ListCell   *cell;
  			save_buffer *existing_slot = NULL,
  					   *free_slot = NULL;
  			StringInfo	str;
  
  			chunklen = PIPE_HEADER_SIZE + p.len;
  
  			/* Fall out of loop if we don't have the whole chunk yet */
  			if (count < chunklen)
  				break;
  
  			if ((p.flags & PIPE_PROTO_DEST_STDERR) != 0)
  				dest = LOG_DESTINATION_STDERR;
  			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
  				dest = LOG_DESTINATION_CSVLOG;
  			else
  			{
  				/* this should never happen as of the header validation */
  				Assert(false);
  			}
  
  			/* Locate any existing buffer for this source pid */
  			buffer_list = buffer_lists[p.pid % NBUFFER_LISTS];
  			foreach(cell, buffer_list)
  			{
  				save_buffer *buf = (save_buffer *) lfirst(cell);
  
  				if (buf->pid == p.pid)
  				{
  					existing_slot = buf;
  					break;
  				}
  				if (buf->pid == 0 && free_slot == NULL)
  					free_slot = buf;
  			}
  
  			if ((p.flags & PIPE_PROTO_IS_LAST) == 0)
  			{
  				/*
  				 * Save a complete non-final chunk in a per-pid buffer
  				 */
  				if (existing_slot != NULL)
  				{
  					/* Add chunk to data from preceding chunks */
  					str = &(existing_slot->data);
  					appendBinaryStringInfo(str,
  										   cursor + PIPE_HEADER_SIZE,
  										   p.len);
  				}
  				else
  				{
  					/* First chunk of message, save in a new buffer */
  					if (free_slot == NULL)
  					{
  						/*
  						 * Need a free slot, but there isn't one in the list,
  						 * so create a new one and extend the list with it.
  						 */
  						free_slot = palloc(sizeof(save_buffer));
  						buffer_list = lappend(buffer_list, free_slot);
  						buffer_lists[p.pid % NBUFFER_LISTS] = buffer_list;
  					}
  					free_slot->pid = p.pid;
  					str = &(free_slot->data);
  					initStringInfo(str);
  					appendBinaryStringInfo(str,
  										   cursor + PIPE_HEADER_SIZE,
  										   p.len);
  				}
  			}
  			else
  			{
  				/*
  				 * Final chunk --- add it to anything saved for that pid, and
  				 * either way write the whole thing out.
  				 */
  				if (existing_slot != NULL)
  				{
  					str = &(existing_slot->data);
  					appendBinaryStringInfo(str,
  										   cursor + PIPE_HEADER_SIZE,
  										   p.len);
  					write_syslogger_file(str->data, str->len, dest);
  					/* Mark the buffer unused, and reclaim string storage */
  					existing_slot->pid = 0;
  					pfree(str->data);
  				}
  				else
  				{
  					/* The whole message was one chunk, evidently. */
  					write_syslogger_file(cursor + PIPE_HEADER_SIZE, p.len,
  										 dest);
  				}
  			}
  
  			/* Finished processing this chunk */
  			cursor += chunklen;
  			count -= chunklen;
  		}
  		else
  		{
  			/* Process non-protocol data */
  
  			/*
  			 * Look for the start of a protocol header.  If found, dump data
  			 * up to there and repeat the loop.  Otherwise, dump it all and
  			 * fall out of the loop.  (Note: we want to dump it all if at all
  			 * possible, so as to avoid dividing non-protocol messages across
  			 * logfiles.  We expect that in many scenarios, a non-protocol
  			 * message will arrive all in one read(), and we want to respect
  			 * the read() boundary if possible.)
  			 */
  			for (chunklen = 1; chunklen < count; chunklen++)
  			{
  				if (cursor[chunklen] == '\0')
  					break;
  			}
  			/* fall back on the stderr log as the destination */
  			write_syslogger_file(cursor, chunklen, LOG_DESTINATION_STDERR);
  			cursor += chunklen;
  			count -= chunklen;
  		}
  	}
  
  	/* We don't have a full chunk, so left-align what remains in the buffer */
  	if (count > 0 && cursor != logbuffer)
  		memmove(logbuffer, cursor, count);
  	*bytes_in_logbuffer = count;
  }
  
  /*
   * Force out any buffered data
   *
   * This is currently used only at syslogger shutdown, but could perhaps be
   * useful at other times, so it is careful to leave things in a clean state.
   */
  static void
  flush_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
  {
  	int			i;
  
  	/* Dump any incomplete protocol messages */
  	for (i = 0; i < NBUFFER_LISTS; i++)
  	{
  		List	   *list = buffer_lists[i];
  		ListCell   *cell;
  
  		foreach(cell, list)
  		{
  			save_buffer *buf = (save_buffer *) lfirst(cell);
  
  			if (buf->pid != 0)
  			{
  				StringInfo	str = &(buf->data);
  
  				write_syslogger_file(str->data, str->len,
  									 LOG_DESTINATION_STDERR);
  				/* Mark the buffer unused, and reclaim string storage */
  				buf->pid = 0;
  				pfree(str->data);
  			}
  		}
  	}
  
  	/*
  	 * Force out any remaining pipe data as-is; we don't bother trying to
  	 * remove any protocol headers that may exist in it.
  	 */
  	if (*bytes_in_logbuffer > 0)
  		write_syslogger_file(logbuffer, *bytes_in_logbuffer,
  							 LOG_DESTINATION_STDERR);
  	*bytes_in_logbuffer = 0;
  }
  
  
  /* --------------------------------
   *		logfile routines
   * --------------------------------
   */
  
  /*
   * Write text to the currently open logfile
   *
   * This is exported so that elog.c can call it when MyBackendType is B_LOGGER.
   * 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, int destination)
  {
  	int			rc;
  	FILE	   *logfile;
  
  	/*
  	 * If we're told to write to csvlogFile, but it's not open, dump the data
  	 * to syslogFile (which is always open) instead.  This can happen if CSV
  	 * output is enabled after postmaster start and we've been unable to open
  	 * csvlogFile.  There are also race conditions during a parameter change
  	 * whereby backends might send us CSV output before we open csvlogFile or
  	 * after we close it.  Writing CSV-formatted output to the regular log
  	 * file isn't great, but it beats dropping log output on the floor.
  	 *
  	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
  	 * failure in that would lead to recursion.
  	 */
  	logfile = (destination == LOG_DESTINATION_CSVLOG &&
  			   csvlogFile != NULL) ? csvlogFile : syslogFile;
  
  	rc = fwrite(buffer, 1, count, logfile);
  
  	/*
  	 * Try to report any failure.  We mustn't use ereport because it would
  	 * just recurse right back here, but write_stderr is OK: it will write
  	 * either to the postmaster's original stderr, or to /dev/null, but never
  	 * to our input pipe which would result in a different sort of looping.
  	 */
  	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, WaitForMultipleObjects 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)
  {
  	char		logbuffer[READ_BUF_SIZE];
  	int			bytes_in_logbuffer = 0;
  
  	for (;;)
  	{
  		DWORD		bytesRead;
  		BOOL		result;
  
  		result = ReadFile(syslogPipe[0],
  						  logbuffer + bytes_in_logbuffer,
  						  sizeof(logbuffer) - bytes_in_logbuffer,
  						  &bytesRead, 0);
  
  		/*
  		 * Enter critical section before doing anything that might touch
  		 * global state shared by the main thread. Anything that uses
  		 * palloc()/pfree() in particular are not safe outside the critical
  		 * section.
  		 */
  		EnterCriticalSection(&sysloggerSection);
  		if (!result)
  		{
  			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)
  		{
  			bytes_in_logbuffer += bytesRead;
  			process_pipe_input(logbuffer, &bytes_in_logbuffer);
  		}
  
  		/*
  		 * If we've filled the current logfile, nudge the main thread to do a
  		 * log rotation.
  		 */
  		if (Log_RotationSize > 0)
  		{
  			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
  				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
  				SetLatch(MyLatch);
  		}
  		LeaveCriticalSection(&sysloggerSection);
  	}
  
  	/* We exit the above loop only upon detecting pipe EOF */
  	pipe_eof_seen = true;
  
  	/* if there's any data left then force it out now */
  	flush_pipe_input(logbuffer, &bytes_in_logbuffer);
  
  	/* set the latch to waken the main thread, which will quit */
  	SetLatch(MyLatch);
  
  	LeaveCriticalSection(&sysloggerSection);
  	_endthread();
  	return 0;
  }
  #endif							/* WIN32 */
  
  /*
   * Open a new logfile with proper permissions and buffering options.
   *
   * If allow_errors is true, we just log any open failure and return NULL
   * (with errno still correct for the fopen failure).
   * Otherwise, errors are treated as fatal.
   */
  static FILE *
  logfile_open(const char *filename, const char *mode, bool allow_errors)
  {
  	FILE	   *fh;
  	mode_t		oumask;
  
  	/*
  	 * Note we do not let Log_file_mode disable IWUSR, since we certainly want
  	 * to be able to write the files ourselves.
  	 */
  	oumask = umask((mode_t) ((~(Log_file_mode | S_IWUSR)) & (S_IRWXU | S_IRWXG | S_IRWXO)));
  	fh = fopen(filename, mode);
  	umask(oumask);
  
  	if (fh)
  	{
  		setvbuf(fh, NULL, PG_IOLBF, 0);
  
  #ifdef WIN32
  		/* use CRLF line endings on Windows */
  		_setmode(_fileno(fh), _O_TEXT);
  #endif
  	}
  	else
  	{
  		int			save_errno = errno;
  
  		ereport(allow_errors ? LOG : FATAL,
  				(errcode_for_file_access(),
  				 errmsg("could not open log file \"%s\": %m",
  						filename)));
  		errno = save_errno;
  	}
  
  	return fh;
  }
  
  /*
   * Do logfile rotation for a single destination, as specified by target_dest.
   * The information stored in *last_file_name and *logFile is updated on a
   * successful file rotation.
   *
   * Returns false if the rotation has been stopped, or true to move on to
   * the processing of other formats.
   */
  static bool
  logfile_rotate_dest(bool time_based_rotation, int size_rotation_for,
  					pg_time_t fntime, int target_dest,
  					char **last_file_name, FILE **logFile)
  {
  	char	   *logFileExt = NULL;
  	char	   *filename;
  	FILE	   *fh;
  
  	/*
  	 * If the target destination was just turned off, close the previous file
  	 * and unregister its data.  This cannot happen for stderr as syslogFile
  	 * is assumed to be always opened even if stderr is disabled in
  	 * log_destination.
  	 */
  	if ((Log_destination & target_dest) == 0 &&
  		target_dest != LOG_DESTINATION_STDERR)
  	{
  		if (*logFile != NULL)
  			fclose(*logFile);
  		*logFile = NULL;
  		if (*last_file_name != NULL)
  			pfree(*last_file_name);
  		*last_file_name = NULL;
  		return true;
  	}
  
  	/*
  	 * Leave if it is not time for a rotation or if the target destination has
  	 * no need to do a rotation based on the size of its file.
  	 */
  	if (!time_based_rotation && (size_rotation_for & target_dest) == 0)
  		return true;
  
  	/* file extension depends on the destination type */
  	if (target_dest == LOG_DESTINATION_STDERR)
  		logFileExt = NULL;
  	else if (target_dest == LOG_DESTINATION_CSVLOG)
  		logFileExt = ".csv";
  	else
  	{
  		/* cannot happen */
  		Assert(false);
  	}
  
  	/* build the new file name */
  	filename = logfile_getname(fntime, logFileExt);
  
  	/*
  	 * 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.
  	 */
  	if (Log_truncate_on_rotation && time_based_rotation &&
  		*last_file_name != NULL &&
  		strcmp(filename, *last_file_name) != 0)
  		fh = logfile_open(filename, "w", true);
  	else
  		fh = logfile_open(filename, "a", true);
  
  	if (!fh)
  	{
  		/*
  		 * 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 (errno != ENFILE && errno != EMFILE)
  		{
  			ereport(LOG,
  					(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
  			rotation_disabled = true;
  		}
  
  		if (filename)
  			pfree(filename);
  		return false;
  	}
  
  	/* fill in the new information */
  	if (*logFile != NULL)
  		fclose(*logFile);
  	*logFile = fh;
  
  	/* instead of pfree'ing filename, remember it for next time */
  	if (*last_file_name != NULL)
  		pfree(*last_file_name);
  	*last_file_name = filename;
  
  	return true;
  }
  
  /*
   * perform logfile rotation
   */
  static void
  logfile_rotate(bool time_based_rotation, int size_rotation_for)
  {
  	pg_time_t	fntime;
  
  	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)
  		fntime = next_rotation_time;
  	else
  		fntime = time(NULL);
  
  	/* file rotation for stderr */
  	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
  							 LOG_DESTINATION_STDERR, &last_sys_file_name,
  							 &syslogFile))
  		return;
  
  	/* file rotation for csvlog */
  	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
  							 LOG_DESTINATION_CSVLOG, &last_csv_file_name,
  							 &csvlogFile))
  		return;
  
  	update_metainfo_datafile();
  
  	set_next_rotation_time();
  }
  
  
  /*
   * construct logfile name using timestamp information
   *
   * If suffix isn't NULL, append it to the name, replacing any ".log"
   * that may be in the pattern.
   *
   * Result is palloc'd.
   */
  static char *
  logfile_getname(pg_time_t timestamp, const char *suffix)
  {
  	char	   *filename;
  	int			len;
  
  	filename = palloc(MAXPGPATH);
  
  	snprintf(filename, MAXPGPATH, "%s/", Log_directory);
  
  	len = strlen(filename);
  
  	/* treat Log_filename as a strftime pattern */
  	pg_strftime(filename + len, MAXPGPATH - len, Log_filename,
  				pg_localtime(&timestamp, log_timezone));
  
  	if (suffix != NULL)
  	{
  		len = strlen(filename);
  		if (len > 4 && (strcmp(filename + (len - 4), ".log") == 0))
  			len -= 4;
  		strlcpy(filename + len, suffix, MAXPGPATH - len);
  	}
  
  	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 log_timezone rather than
  	 * GMT.
  	 */
  	rotinterval = Log_RotationAge * SECS_PER_MINUTE;	/* convert to seconds */
  	now = (pg_time_t) time(NULL);
  	tm = pg_localtime(&now, log_timezone);
  	now += tm->tm_gmtoff;
  	now -= now % rotinterval;
  	now += rotinterval;
  	now -= tm->tm_gmtoff;
  	next_rotation_time = now;
  }
  
  /*
   * Store the name of the file(s) where the log collector, when enabled, writes
   * log messages.  Useful for finding the name(s) of the current log file(s)
   * when there is time-based logfile rotation.  Filenames are stored in a
   * temporary file and which is renamed into the final destination for
   * atomicity.  The file is opened with the same permissions as what gets
   * created in the data directory and has proper buffering options.
   */
  static void
  update_metainfo_datafile(void)
  {
  	FILE	   *fh;
  	mode_t		oumask;
  
  	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
  		!(Log_destination & LOG_DESTINATION_CSVLOG))
  	{
  		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
  			ereport(LOG,
  					(errcode_for_file_access(),
  					 errmsg("could not remove file \"%s\": %m",
  							LOG_METAINFO_DATAFILE)));
  		return;
  	}
  
  	/* use the same permissions as the data directory for the new file */
  	oumask = umask(pg_mode_mask);
  	fh = fopen(LOG_METAINFO_DATAFILE_TMP, "w");
  	umask(oumask);
  
  	if (fh)
  	{
  		setvbuf(fh, NULL, PG_IOLBF, 0);
  
  #ifdef WIN32
  		/* use CRLF line endings on Windows */
  		_setmode(_fileno(fh), _O_TEXT);
  #endif
  	}
  	else
  	{
  		ereport(LOG,
  				(errcode_for_file_access(),
  				 errmsg("could not open file \"%s\": %m",
  						LOG_METAINFO_DATAFILE_TMP)));
  		return;
  	}
  
  	if (last_sys_file_name && (Log_destination & LOG_DESTINATION_STDERR))
  	{
  		if (fprintf(fh, "stderr %s\n", last_sys_file_name) < 0)
  		{
  			ereport(LOG,
  					(errcode_for_file_access(),
  					 errmsg("could not write file \"%s\": %m",
  							LOG_METAINFO_DATAFILE_TMP)));
  			fclose(fh);
  			return;
  		}
  	}
  
  	if (last_csv_file_name && (Log_destination & LOG_DESTINATION_CSVLOG))
  	{
  		if (fprintf(fh, "csvlog %s\n", last_csv_file_name) < 0)
  		{
  			ereport(LOG,
  					(errcode_for_file_access(),
  					 errmsg("could not write file \"%s\": %m",
  							LOG_METAINFO_DATAFILE_TMP)));
  			fclose(fh);
  			return;
  		}
  	}
  	fclose(fh);
  
  	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
  		ereport(LOG,
  				(errcode_for_file_access(),
  				 errmsg("could not rename file \"%s\" to \"%s\": %m",
  						LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE)));
  }
  
  /* --------------------------------
   *		signal handler routines
   * --------------------------------
   */
  
  /*
   * Check to see if a log rotation request has arrived.  Should be
   * called by postmaster after receiving SIGUSR1.
   */
  bool
  CheckLogrotateSignal(void)
  {
  	struct stat stat_buf;
  
  	if (stat(LOGROTATE_SIGNAL_FILE, &stat_buf) == 0)
  		return true;
  
  	return false;
  }
  
  /*
   * Remove the file signaling a log rotation request.
   */
  void
  RemoveLogrotateSignalFiles(void)
  {
  	unlink(LOGROTATE_SIGNAL_FILE);
  }
  
  /* SIGUSR1: set flag to rotate logfile */
  static void
  sigUsr1Handler(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	rotation_requested = true;
  	SetLatch(MyLatch);
  
  	errno = save_errno;
  }
  