#include "postgres_fe.h"
#include <ctype.h>
#include <dirent.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/time.h>
#include "pg_getopt.h"
#include "access/xlog_internal.h"

Include dependency graph for pg_standby.c:

Macros
#define	NoFailover 0

#define	SmartFailover 1

#define	FastFailover 2

#define	RESTORE_COMMAND_COPY 0

#define	RESTORE_COMMAND_LINK 1

#define	XLOG_DATA 0

#define	XLOG_HISTORY 1

#define	XLOG_BACKUP_LABEL 2

#define	SET_RESTORE_COMMAND(cmd, arg1, arg2) snprintf(restoreCommand, MAXPGPATH, cmd " \"%s\" \"%s\"", arg1, arg2)

#define	MaxSegmentsPerLogFile ( 0xFFFFFFFF / XLOG_SEG_SIZE )

Functions
static void	CustomizableInitialize (void)

static bool	CustomizableNextWALFileReady (void)

static void	CustomizableCleanupPriorWALFiles (void)

static bool	SetWALFileNameForCleanup (void)

static void	CheckForExternalTrigger (void)

static bool	RestoreWALFileForRecovery (void)

static void	usage (void)

static void	sighandler (int sig)

static void	sigquit_handler (int sig)

int	main (int argc, char **argv)

Variables
const char *	progname

int	sleeptime = 5

int	waittime = -1

int	maxwaittime = 0

int	keepfiles = 0

int	maxretries = 3

bool	debug = false

bool	need_cleanup = false

static volatile sig_atomic_t	signaled = false

char *	archiveLocation

char *	triggerPath

char *	xlogFilePath

char *	nextWALFileName

char *	restartWALFileName

char *	priorWALFileName

char	WALFilePath [MAXPGPATH *2]

char	restoreCommand [MAXPGPATH]

char	exclusiveCleanupFileName [MAXFNAMELEN]

static int	Failover = NoFailover

int	restoreCommandType

int	nextWALFileType

struct stat	stat_buf

Macro Definition Documentation

#define FastFailover 2

Definition at line 85 of file pg_standby.c.

Referenced by CheckForExternalTrigger(), and main().

#define MaxSegmentsPerLogFile ( 0xFFFFFFFF / XLOG_SEG_SIZE )

Definition at line 221 of file pg_standby.c.

Referenced by SetWALFileNameForCleanup().

#define NoFailover 0

Definition at line 83 of file pg_standby.c.

#define RESTORE_COMMAND_COPY 0

Definition at line 89 of file pg_standby.c.

Referenced by CustomizableInitialize(), and main().

#define RESTORE_COMMAND_LINK 1

Definition at line 90 of file pg_standby.c.

Referenced by CustomizableInitialize(), and main().

#define SET_RESTORE_COMMAND	(	cmd,
		arg1,
		arg2
	)	snprintf(restoreCommand, MAXPGPATH, cmd " \"%s\" \"%s\"", arg1, arg2)

Definition at line 98 of file pg_standby.c.

Referenced by CustomizableInitialize().

#define SmartFailover 1

Definition at line 84 of file pg_standby.c.

Referenced by CheckForExternalTrigger(), and main().

#define XLOG_BACKUP_LABEL 2

Definition at line 95 of file pg_standby.c.

Referenced by CustomizableNextWALFileReady().

#define XLOG_DATA 0

Definition at line 93 of file pg_standby.c.

Referenced by CustomizableCleanupPriorWALFiles(), and CustomizableNextWALFileReady().

#define XLOG_HISTORY 1

Definition at line 94 of file pg_standby.c.

Referenced by main().

Function Documentation

static void CheckForExternalTrigger ( void )

static

Definition at line 375 of file pg_standby.c.

References buf, close, Failover, FastFailover, fd(), ftruncate, read, SmartFailover, stat_buf, strerror(), and triggerPath.

Referenced by main().

 {
     char        buf[32];
     int         fd;
     int         len;
 
     /*
      * Look for a trigger file, if that option has been selected
      *
      * We use stat() here because triggerPath is always a file rather than
      * potentially being in an archive
      */
     if (!triggerPath || stat(triggerPath, &stat_buf) != 0)
         return;
 
     /*
      * An empty trigger file performs smart failover. There's a little race
      * condition here: if the writer of the trigger file has just created the
      * file, but not yet written anything to it, we'll treat that as smart
      * shutdown even if the other process was just about to write "fast" to
      * it. But that's fine: we'll restore one more WAL file, and when we're
      * invoked next time, we'll see the word "fast" and fail over immediately.
      */
     if (stat_buf.st_size == 0)
     {
         Failover = SmartFailover;
         fprintf(stderr, "trigger file found: smart failover\n");
         fflush(stderr);
         return;
     }
 
     if ((fd = open(triggerPath, O_RDWR, 0)) < 0)
     {
         fprintf(stderr, "WARNING: could not open \"%s\": %s\n",
                 triggerPath, strerror(errno));
         fflush(stderr);
         return;
     }
 
     if ((len = read(fd, buf, sizeof(buf) - 1)) < 0)
     {
         fprintf(stderr, "WARNING: could not read \"%s\": %s\n",
                 triggerPath, strerror(errno));
         fflush(stderr);
         close(fd);
         return;
     }
     buf[len] = '\0';
 
     if (strncmp(buf, "smart", 5) == 0)
     {
         Failover = SmartFailover;
         fprintf(stderr, "trigger file found: smart failover\n");
         fflush(stderr);
         close(fd);
         return;
     }
 
     if (strncmp(buf, "fast", 4) == 0)
     {
         Failover = FastFailover;
 
         fprintf(stderr, "trigger file found: fast failover\n");
         fflush(stderr);
 
         /*
          * Turn it into a "smart" trigger by truncating the file. Otherwise if
          * the server asks us again to restore a segment that was restored
          * already, we would return "not found" and upset the server.
          */
         if (ftruncate(fd, 0) < 0)
         {
             fprintf(stderr, "WARNING: could not read \"%s\": %s\n",
                     triggerPath, strerror(errno));
             fflush(stderr);
         }
         close(fd);
 
         return;
     }
     close(fd);
 
     fprintf(stderr, "WARNING: invalid content in \"%s\"\n", triggerPath);
     fflush(stderr);
     return;
 }

static void CustomizableCleanupPriorWALFiles ( void )

static

Definition at line 224 of file pg_standby.c.

References archiveLocation, closedir(), dirent::d_name, debug, exclusiveCleanupFileName, IsXLogFileName, nextWALFileType, NULL, opendir(), progname, readdir(), snprintf(), strerror(), unlink(), WALFilePath, and XLOG_DATA.

Referenced by main().

 {
     /*
      * Work out name of prior file from current filename
      */
     if (nextWALFileType == XLOG_DATA)
     {
         int         rc;
         DIR        *xldir;
         struct dirent *xlde;
 
         /*
          * Assume it's OK to keep failing. The failure situation may change
          * over time, so we'd rather keep going on the main processing than
          * fail because we couldn't clean up yet.
          */
         if ((xldir = opendir(archiveLocation)) != NULL)
         {
             while (errno = 0, (xlde = readdir(xldir)) != NULL)
             {
                 /*
                  * We ignore the timeline part of the XLOG segment identifiers
                  * in deciding whether a segment is still needed.  This
                  * ensures that we won't prematurely remove a segment from a
                  * parent timeline. We could probably be a little more
                  * proactive about removing segments of non-parent timelines,
                  * but that would be a whole lot more complicated.
                  *
                  * We use the alphanumeric sorting property of the filenames
                  * to decide which ones are earlier than the
                  * exclusiveCleanupFileName file. Note that this means files
                  * are not removed in the order they were originally written,
                  * in case this worries you.
                  */
                 if (IsXLogFileName(xlde->d_name) &&
                     strcmp(xlde->d_name + 8, exclusiveCleanupFileName + 8) < 0)
                 {
 #ifdef WIN32
                     snprintf(WALFilePath, sizeof(WALFilePath), "%s\\%s", archiveLocation, xlde->d_name);
 #else
                     snprintf(WALFilePath, sizeof(WALFilePath), "%s/%s", archiveLocation, xlde->d_name);
 #endif
 
                     if (debug)
                         fprintf(stderr, "\nremoving file \"%s\"", WALFilePath);
 
                     rc = unlink(WALFilePath);
                     if (rc != 0)
                     {
                         fprintf(stderr, "\n%s: ERROR: could not remove file \"%s\": %s\n",
                                 progname, WALFilePath, strerror(errno));
                         break;
                     }
                 }
             }
 
             if (errno)
                 fprintf(stderr, "%s: could not read archive location \"%s\": %s\n",
                         progname, archiveLocation, strerror(errno));
             if (debug)
                 fprintf(stderr, "\n");
         }
         else
             fprintf(stderr, "%s: could not open archive location \"%s\": %s\n",
                     progname, archiveLocation, strerror(errno));
 
         if (closedir(xldir))
             fprintf(stderr, "%s: could not close archive location \"%s\": %s\n",
                     progname, archiveLocation, strerror(errno));
 
         fflush(stderr);
     }
 }

static void CustomizableInitialize ( void )

static

Definition at line 125 of file pg_standby.c.

References archiveLocation, MAXPGPATH, nextWALFileName, progname, RESTORE_COMMAND_COPY, RESTORE_COMMAND_LINK, restoreCommandType, SET_RESTORE_COMMAND, snprintf(), stat_buf, WALFilePath, and xlogFilePath.

Referenced by main().

 {
 #ifdef WIN32
     snprintf(WALFilePath, MAXPGPATH, "%s\\%s", archiveLocation, nextWALFileName);
     switch (restoreCommandType)
     {
         case RESTORE_COMMAND_LINK:
             SET_RESTORE_COMMAND("mklink", WALFilePath, xlogFilePath);
             break;
         case RESTORE_COMMAND_COPY:
         default:
             SET_RESTORE_COMMAND("copy", WALFilePath, xlogFilePath);
             break;
     }
 #else
     snprintf(WALFilePath, MAXPGPATH, "%s/%s", archiveLocation, nextWALFileName);
     switch (restoreCommandType)
     {
         case RESTORE_COMMAND_LINK:
 #if HAVE_WORKING_LINK
             SET_RESTORE_COMMAND("ln -s -f", WALFilePath, xlogFilePath);
             break;
 #endif
         case RESTORE_COMMAND_COPY:
         default:
             SET_RESTORE_COMMAND("cp", WALFilePath, xlogFilePath);
             break;
     }
 #endif
 
     /*
      * This code assumes that archiveLocation is a directory You may wish to
      * add code to check for tape libraries, etc.. So, since it is a
      * directory, we use stat to test if it's accessible
      */
     if (stat(archiveLocation, &stat_buf) != 0)
     {
         fprintf(stderr, "%s: archive location \"%s\" does not exist\n", progname, archiveLocation);
         fflush(stderr);
         exit(2);
     }
 }

static bool CustomizableNextWALFileReady ( void )

static

Definition at line 174 of file pg_standby.c.

References debug, IsBackupHistoryFileName, nextWALFileName, nextWALFileType, pg_usleep(), sleeptime, stat_buf, WALFilePath, XLOG_BACKUP_LABEL, and XLOG_DATA.

Referenced by main().

 {
     if (stat(WALFilePath, &stat_buf) == 0)
     {
         /*
          * If it's a backup file, return immediately. If it's a regular file
          * return only if it's the right size already.
          */
         if (IsBackupHistoryFileName(nextWALFileName))
         {
             nextWALFileType = XLOG_BACKUP_LABEL;
             return true;
         }
         else if (stat_buf.st_size == XLOG_SEG_SIZE)
         {
 #ifdef WIN32
 
             /*
              * Windows 'cp' sets the final file size before the copy is
              * complete, and not yet ready to be opened by pg_standby. So we
              * wait for sleeptime secs before attempting to restore. If that
              * is not enough, we will rely on the retry/holdoff mechanism.
              * GNUWin32's cp does not have this problem.
              */
             pg_usleep(sleeptime * 1000000L);
 #endif
             nextWALFileType = XLOG_DATA;
             return true;
         }
 
         /*
          * If still too small, wait until it is the correct size
          */
         if (stat_buf.st_size > XLOG_SEG_SIZE)
         {
             if (debug)
             {
                 fprintf(stderr, "file size greater than expected\n");
                 fflush(stderr);
             }
             exit(3);
         }
     }
 
     return false;
 }

int main	(	int	argc,
		char **	argv
	)

Definition at line 548 of file pg_standby.c.

References archiveLocation, CheckForExternalTrigger(), CustomizableCleanupPriorWALFiles(), CustomizableInitialize(), CustomizableNextWALFileReady(), debug, exclusiveCleanupFileName, Failover, FastFailover, get_progname(), getopt(), IsTLHistoryFileName, keepfiles, maxretries, maxwaittime, need_cleanup, nextWALFileName, nextWALFileType, optarg, optind, pg_strdup(), pg_usleep(), pqsignal(), progname, restartWALFileName, RESTORE_COMMAND_COPY, RESTORE_COMMAND_LINK, restoreCommand, restoreCommandType, RestoreWALFileForRecovery(), SetWALFileNameForCleanup(), sighandler(), signaled, SIGQUIT, sigquit_handler(), SIGUSR1, sleeptime, SmartFailover, triggerPath, usage(), waittime, WALFilePath, XLOG_HISTORY, and xlogFilePath.

 {
     int         c;
 
     progname = get_progname(argv[0]);
 
     if (argc > 1)
     {
         if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-?") == 0)
         {
             usage();
             exit(0);
         }
         if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0)
         {
             puts("pg_standby (PostgreSQL) " PG_VERSION);
             exit(0);
         }
     }
 
 #ifndef WIN32
 
     /*
      * You can send SIGUSR1 to trigger failover.
      *
      * Postmaster uses SIGQUIT to request immediate shutdown. The default
      * action is to core dump, but we don't want that, so trap it and commit
      * suicide without core dump.
      *
      * We used to use SIGINT and SIGQUIT to trigger failover, but that turned
      * out to be a bad idea because postmaster uses SIGQUIT to request
      * immediate shutdown. We still trap SIGINT, but that may change in a
      * future release.
      *
      * There's no way to trigger failover via signal on Windows.
      */
     (void) pqsignal(SIGUSR1, sighandler);
     (void) pqsignal(SIGINT, sighandler);    /* deprecated, use SIGUSR1 */
     (void) pqsignal(SIGQUIT, sigquit_handler);
 #endif
 
     while ((c = getopt(argc, argv, "cdk:lr:s:t:w:")) != -1)
     {
         switch (c)
         {
             case 'c':           /* Use copy */
                 restoreCommandType = RESTORE_COMMAND_COPY;
                 break;
             case 'd':           /* Debug mode */
                 debug = true;
                 break;
             case 'k':           /* keepfiles */
                 keepfiles = atoi(optarg);
                 if (keepfiles < 0)
                 {
                     fprintf(stderr, "%s: -k keepfiles must be >= 0\n", progname);
                     exit(2);
                 }
                 break;
             case 'l':           /* Use link */
 
                 /*
                  * Link feature disabled, possibly permanently. Linking causes
                  * a problem after recovery ends that is not currently
                  * resolved by PostgreSQL. 25 Jun 2009
                  */
 #ifdef NOT_USED
                 restoreCommandType = RESTORE_COMMAND_LINK;
 #endif
                 break;
             case 'r':           /* Retries */
                 maxretries = atoi(optarg);
                 if (maxretries < 0)
                 {
                     fprintf(stderr, "%s: -r maxretries must be >= 0\n", progname);
                     exit(2);
                 }
                 break;
             case 's':           /* Sleep time */
                 sleeptime = atoi(optarg);
                 if (sleeptime <= 0 || sleeptime > 60)
                 {
                     fprintf(stderr, "%s: -s sleeptime incorrectly set\n", progname);
                     exit(2);
                 }
                 break;
             case 't':           /* Trigger file */
                 triggerPath = pg_strdup(optarg);
                 break;
             case 'w':           /* Max wait time */
                 maxwaittime = atoi(optarg);
                 if (maxwaittime < 0)
                 {
                     fprintf(stderr, "%s: -w maxwaittime incorrectly set\n", progname);
                     exit(2);
                 }
                 break;
             default:
                 fprintf(stderr, "Try \"%s --help\" for more information.\n", progname);
                 exit(2);
                 break;
         }
     }
 
     /*
      * Parameter checking - after checking to see if trigger file present
      */
     if (argc == 1)
     {
         fprintf(stderr, "%s: not enough command-line arguments\n", progname);
         exit(2);
     }
 
     /*
      * We will go to the archiveLocation to get nextWALFileName.
      * nextWALFileName may not exist yet, which would not be an error, so we
      * separate the archiveLocation and nextWALFileName so we can check
      * separately whether archiveLocation exists, if not that is an error
      */
     if (optind < argc)
     {
         archiveLocation = argv[optind];
         optind++;
     }
     else
     {
         fprintf(stderr, "%s: must specify archive location\n", progname);
         fprintf(stderr, "Try \"%s --help\" for more information.\n", progname);
         exit(2);
     }
 
     if (optind < argc)
     {
         nextWALFileName = argv[optind];
         optind++;
     }
     else
     {
         fprintf(stderr, "%s: must specify WAL file name as second non-option argument (use \"%%f\")\n", progname);
         fprintf(stderr, "Try \"%s --help\" for more information.\n", progname);
         exit(2);
     }
 
     if (optind < argc)
     {
         xlogFilePath = argv[optind];
         optind++;
     }
     else
     {
         fprintf(stderr, "%s: must specify xlog destination as third non-option argument (use \"%%p\")\n", progname);
         fprintf(stderr, "Try \"%s --help\" for more information.\n", progname);
         exit(2);
     }
 
     if (optind < argc)
     {
         restartWALFileName = argv[optind];
         optind++;
     }
 
     CustomizableInitialize();
 
     need_cleanup = SetWALFileNameForCleanup();
 
     if (debug)
     {
         fprintf(stderr, "Trigger file:         %s\n", triggerPath ? triggerPath : "<not set>");
         fprintf(stderr, "Waiting for WAL file: %s\n", nextWALFileName);
         fprintf(stderr, "WAL file path:        %s\n", WALFilePath);
         fprintf(stderr, "Restoring to:         %s\n", xlogFilePath);
         fprintf(stderr, "Sleep interval:       %d second%s\n",
                 sleeptime, (sleeptime > 1 ? "s" : " "));
         fprintf(stderr, "Max wait interval:    %d %s\n",
                 maxwaittime, (maxwaittime > 0 ? "seconds" : "forever"));
         fprintf(stderr, "Command for restore:  %s\n", restoreCommand);
         fprintf(stderr, "Keep archive history: ");
         if (need_cleanup)
             fprintf(stderr, "%s and later\n", exclusiveCleanupFileName);
         else
             fprintf(stderr, "no cleanup required\n");
         fflush(stderr);
     }
 
     /*
      * Check for initial history file: always the first file to be requested
      * It's OK if the file isn't there - all other files need to wait
      */
     if (IsTLHistoryFileName(nextWALFileName))
     {
         nextWALFileType = XLOG_HISTORY;
         if (RestoreWALFileForRecovery())
             exit(0);
         else
         {
             if (debug)
             {
                 fprintf(stderr, "history file not found\n");
                 fflush(stderr);
             }
             exit(1);
         }
     }
 
     /*
      * Main wait loop
      */
     for (;;)
     {
         /* Check for trigger file or signal first */
         CheckForExternalTrigger();
 #ifndef WIN32
         if (signaled)
         {
             Failover = FastFailover;
             if (debug)
             {
                 fprintf(stderr, "signaled to exit: fast failover\n");
                 fflush(stderr);
             }
         }
 #endif
 
         /*
          * Check for fast failover immediately, before checking if the
          * requested WAL file is available
          */
         if (Failover == FastFailover)
             exit(1);
 
         if (CustomizableNextWALFileReady())
         {
             /*
              * Once we have restored this file successfully we can remove some
              * prior WAL files. If this restore fails we mustn't remove any
              * file because some of them will be requested again immediately
              * after the failed restore, or when we restart recovery.
              */
             if (RestoreWALFileForRecovery())
             {
                 if (need_cleanup)
                     CustomizableCleanupPriorWALFiles();
 
                 exit(0);
             }
             else
             {
                 /* Something went wrong in copying the file */
                 exit(1);
             }
         }
 
         /* Check for smart failover if the next WAL file was not available */
         if (Failover == SmartFailover)
             exit(1);
 
         if (sleeptime <= 60)
             pg_usleep(sleeptime * 1000000L);
 
         waittime += sleeptime;
         if (waittime >= maxwaittime && maxwaittime > 0)
         {
             Failover = FastFailover;
             if (debug)
             {
                 fprintf(stderr, "Timed out after %d seconds: fast failover\n",
                         waittime);
                 fflush(stderr);
             }
         }
         if (debug)
         {
             fprintf(stderr, "WAL file not present yet.");
             if (triggerPath)
                 fprintf(stderr, " Checking for trigger file...");
             fprintf(stderr, "\n");
             fflush(stderr);
         }
     }
 }

static bool RestoreWALFileForRecovery ( void )

static

Definition at line 468 of file pg_standby.c.

References debug, maxretries, pg_usleep(), restoreCommand, and sleeptime.

Referenced by main().

 {
     int         rc = 0;
     int         numretries = 0;
 
     if (debug)
     {
         fprintf(stderr, "running restore:      ");
         fflush(stderr);
     }
 
     while (numretries <= maxretries)
     {
         rc = system(restoreCommand);
         if (rc == 0)
         {
             if (debug)
             {
                 fprintf(stderr, "OK\n");
                 fflush(stderr);
             }
             return true;
         }
         pg_usleep(numretries++ * sleeptime * 1000000L);
     }
 
     /*
      * Allow caller to add additional info
      */
     if (debug)
         fprintf(stderr, "not restored\n");
     return false;
 }

static bool SetWALFileNameForCleanup ( void )

static

Definition at line 310 of file pg_standby.c.

References cleanup(), exclusiveCleanupFileName, keepfiles, MaxSegmentsPerLogFile, nextWALFileName, restartWALFileName, strlcpy(), and XLogFileNameById.

Referenced by main().

 {
     uint32      tli = 1,
                 log = 0,
                 seg = 0;
     uint32      log_diff = 0,
                 seg_diff = 0;
     bool        cleanup = false;
 
     if (restartWALFileName)
     {
         /*
          * Don't do cleanup if the restartWALFileName provided is later than
          * the xlog file requested. This is an error and we must not remove
          * these files from archive. This shouldn't happen, but better safe
          * than sorry.
          */
         if (strcmp(restartWALFileName, nextWALFileName) > 0)
             return false;
 
         strlcpy(exclusiveCleanupFileName, restartWALFileName, sizeof(exclusiveCleanupFileName));
         return true;
     }
 
     if (keepfiles > 0)
     {
         sscanf(nextWALFileName, "%08X%08X%08X", &tli, &log, &seg);
         if (tli > 0 && seg > 0)
         {
             log_diff = keepfiles / MaxSegmentsPerLogFile;
             seg_diff = keepfiles % MaxSegmentsPerLogFile;
             if (seg_diff > seg)
             {
                 log_diff++;
                 seg = MaxSegmentsPerLogFile - (seg_diff - seg);
             }
             else
                 seg -= seg_diff;
 
             if (log >= log_diff)
             {
                 log -= log_diff;
                 cleanup = true;
             }
             else
             {
                 log = 0;
                 seg = 0;
             }
         }
     }
 
     XLogFileNameById(exclusiveCleanupFileName, tli, log, seg);
 
     return cleanup;
 }

static void sighandler ( int sig )

static

Definition at line 532 of file pg_standby.c.

References signaled.

Referenced by main().

 {
     signaled = true;
 }

static void sigquit_handler ( int sig )

static

Definition at line 539 of file pg_standby.c.

References pqsignal(), and SIG_DFL.

Referenced by main().

 {
     pqsignal(SIGINT, SIG_DFL);
     kill(getpid(), SIGINT);
 }

static void usage ( void )

static

Definition at line 503 of file pg_standby.c.

References progname.

Referenced by exec_command_slash_command_help(), main(), parse_psql_options(), and pg_notification_queue_usage().

 {
     printf("%s allows PostgreSQL warm standby servers to be configured.\n\n", progname);
     printf("Usage:\n");
     printf("  %s [OPTION]... ARCHIVELOCATION NEXTWALFILE XLOGFILEPATH [RESTARTWALFILE]\n", progname);
     printf("\nOptions:\n");
     printf("  -c                 copy file from archive (default)\n");
     printf("  -d                 generate lots of debugging output (testing only)\n");
     printf("  -k NUMFILESTOKEEP  if RESTARTWALFILE is not used, remove files prior to limit\n"
            "                     (0 keeps all)\n");
     printf("  -l                 does nothing; use of link is now deprecated\n");
     printf("  -r MAXRETRIES      max number of times to retry, with progressive wait\n"
            "                     (default=3)\n");
     printf("  -s SLEEPTIME       seconds to wait between file checks (min=1, max=60,\n"
            "                     default=5)\n");
     printf("  -t TRIGGERFILE     trigger file to initiate failover (no default)\n");
     printf("  -V, --version      output version information, then exit\n");
     printf("  -w MAXWAITTIME     max seconds to wait for a file (0=no limit) (default=0)\n");
     printf("  -?, --help         show this help, then exit\n");
     printf("\n"
            "Main intended use as restore_command in recovery.conf:\n"
            "  restore_command = 'pg_standby [OPTION]... ARCHIVELOCATION %%f %%p %%r'\n"
            "e.g.\n"
            "  restore_command = 'pg_standby /mnt/server/archiverdir %%f %%p %%r'\n");
     printf("\nReport bugs to <pgsql-bugs@postgresql.org>.\n");
 }