/*
* $PostgreSQL: pgsql/contrib/pg_standby/pg_standby.c,v 1.20 2009/03/18 20:30:35 heikki Exp $
*
*
* pg_standby.c
*
* Production-ready example of how to create a Warm Standby
* database server using continuous archiving as a
* replication mechanism
*
* We separate the parameters for archive and nextWALfile
* so that we can check the archive exists, even if the
* WAL file doesn't (yet).
*
* This program will be executed once in full for each file
* requested by the warm standby server.
*
* It is designed to cater to a variety of needs, as well
* providing a customizable section.
*
* Original author: Simon Riggs simon@2ndquadrant.com
* Current maintainer: Simon Riggs
*/
#include "postgres_fe.h"
#include <ctype.h>
#include <dirent.h>
#include <sys/stat.h>
#include <signal.h>
#ifdef WIN32
int getopt(int argc, char *const argv[], const char *optstring);
#else
#include <sys/time.h>
#include <unistd.h>
#ifdef HAVE_GETOPT_H
#include <getopt.h>
#endif
#endif /* ! WIN32 */
extern char *optarg;
extern int optind;
const char *progname;
/* Options and defaults */
int sleeptime = 5; /* amount of time to sleep between file checks */
int waittime = -1; /* how long we have been waiting, -1 no wait
* yet */
int maxwaittime = 0; /* how long are we prepared to wait for? */
int keepfiles = 0; /* number of WAL files to keep, 0 keep all */
int maxretries = 3; /* number of retries on restore command */
bool debug = false; /* are we debugging? */
bool triggered = false; /* have we been triggered? */
bool need_cleanup = false; /* do we need to remove files from
* archive? */
static volatile sig_atomic_t signaled = false;
char *archiveLocation; /* where to find the archive? */
char *triggerPath; /* where to find the trigger file? */
char *xlogFilePath; /* where we are going to restore to */
char *nextWALFileName; /* the file we need to get from archive */
char *restartWALFileName; /* the file from which we can restart restore */
char *priorWALFileName; /* the file we need to get from archive */
char WALFilePath[MAXPGPATH]; /* the file path including archive */
char restoreCommand[MAXPGPATH]; /* run this to restore */
char exclusiveCleanupFileName[MAXPGPATH]; /* the file we need to
* get from archive */
#define RESTORE_COMMAND_COPY 0
#define RESTORE_COMMAND_LINK 1
int restoreCommandType;
#define XLOG_DATA 0
#define XLOG_HISTORY 1
#define XLOG_BACKUP_LABEL 2
int nextWALFileType;
#define SET_RESTORE_COMMAND(cmd, arg1, arg2) \
snprintf(restoreCommand, MAXPGPATH, cmd " \"%s\" \"%s\"", arg1, arg2)
struct stat stat_buf;
/* =====================================================================
*
* Customizable section
*
* =====================================================================
*
* Currently, this section assumes that the Archive is a locally
* accessible directory. If you want to make other assumptions,
* such as using a vendor-specific archive and access API, these
* routines are the ones you'll need to change. You're
* enouraged to submit any changes to pgsql-hackers@postgresql.org
* or personally to the current maintainer. Those changes may be
* folded in to later versions of this program.
*/
#define XLOG_DATA_FNAME_LEN 24
/* Reworked from access/xlog_internal.h */
#define XLogFileName(fname, tli, log, seg) \
snprintf(fname, XLOG_DATA_FNAME_LEN + 1, "%08X%08X%08X", tli, log, seg)
/*
* Initialize allows customized commands into the warm standby program.
*
* As an example, and probably the common case, we use either
* cp/ln commands on *nix, or copy/move command on Windows.
*
*/
static void
CustomizableInitialize(void)
{
#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 its accessible
*/
if (stat(archiveLocation, &stat_buf) != 0)
{
fprintf(stderr, "%s: archiveLocation \"%s\" does not exist\n", progname, archiveLocation);
fflush(stderr);
exit(2);
}
}
/*
* CustomizableNextWALFileReady()
*
* Is the requested file ready yet?
*/
static bool
CustomizableNextWALFileReady()
{
if (stat(WALFilePath, &stat_buf) == 0)
{
/*
* If its a backup file, return immediately If its a regular file
* return only if its the right size already
*/
if (strlen(nextWALFileName) > 24 &&
strspn(nextWALFileName, "0123456789ABCDEF") == 24 &&
strcmp(nextWALFileName + strlen(nextWALFileName) - strlen(".backup"),
".backup") == 0)
{
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;
}
#define MaxSegmentsPerLogFile ( 0xFFFFFFFF / XLOG_SEG_SIZE )
static void
CustomizableCleanupPriorWALFiles(void)
{
/*
* Work out name of prior file from current filename
*/
if (nextWALFileType == XLOG_DATA)
{
int rc;
DIR *xldir;
struct dirent *xlde;
/*
* Assume its 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 couldnt clean up yet.
*/
if ((xldir = opendir(archiveLocation)) != NULL)
{
while ((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 (strlen(xlde->d_name) == XLOG_DATA_FNAME_LEN &&
strspn(xlde->d_name, "0123456789ABCDEF") == XLOG_DATA_FNAME_LEN &&
strcmp(xlde->d_name + 8, exclusiveCleanupFileName + 8) < 0)
{
#ifdef WIN32
snprintf(WALFilePath, MAXPGPATH, "%s\\%s", archiveLocation, xlde->d_name);
#else
snprintf(WALFilePath, MAXPGPATH, "%s/%s", archiveLocation, xlde->d_name);
#endif
if (debug)
fprintf(stderr, "\nremoving \"%s\"", WALFilePath);
rc = unlink(WALFilePath);
if (rc != 0)
{
fprintf(stderr, "\n%s: ERROR failed to remove \"%s\": %s",
progname, WALFilePath, strerror(errno));
break;
}
}
}
if (debug)
fprintf(stderr, "\n");
}
else
fprintf(stderr, "%s: archiveLocation \"%s\" open error\n", progname, archiveLocation);
closedir(xldir);
fflush(stderr);
}
}
/* =====================================================================
* End of Customizable section
* =====================================================================
*/
/*
* SetWALFileNameForCleanup()
*
* Set the earliest WAL filename that we want to keep on the archive
* and decide whether we need_cleanup
*/
static bool
SetWALFileNameForCleanup(void)
{
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;
strcpy(exclusiveCleanupFileName, restartWALFileName);
return true;
}
if (keepfiles > 0)
{
sscanf(nextWALFileName, "%08X%08X%08X", &tli, &log, &seg);
if (tli > 0 && log >= 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;
}
}
}
XLogFileName(exclusiveCleanupFileName, tli, log, seg);
return cleanup;
}
/*
* CheckForExternalTrigger()
*
* Is there a trigger file?
*/
static bool
CheckForExternalTrigger(void)
{
int rc;
/*
* 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)
{
fprintf(stderr, "trigger file found\n");
fflush(stderr);
/*
* If trigger file found, we *must* delete it. Here's why: When
* recovery completes, we will be asked again for the same file from
* the archive using pg_standby so must remove trigger file so we can
* reload file again and come up correctly.
*/
rc = unlink(triggerPath);
if (rc != 0)
{
fprintf(stderr, "\n ERROR: could not remove \"%s\": %s", triggerPath, strerror(errno));
fflush(stderr);
exit(rc);
}
return true;
}
return false;
}
/*
* RestoreWALFileForRecovery()
*
* Perform the action required to restore the file from archive
*/
static bool
RestoreWALFileForRecovery(void)
{
int rc = 0;
int numretries = 0;
if (debug)
{
fprintf(stderr, "\nrunning restore :");
fflush(stderr);
}
while (numretries < maxretries)
{
rc = system(restoreCommand);
if (rc == 0)
{
if (debug)
{
fprintf(stderr, " OK");
fflush(stderr);
}
return true;
}
pg_usleep(numretries++ * sleeptime * 1000000L);
}
/*
* Allow caller to add additional info
*/
if (debug)
fprintf(stderr, "not restored : ");
return false;
}
static void
usage(void)
{
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("\n"
"with main intended use as a restore_command in the recovery.conf:\n"
" restore_command = 'pg_standby [OPTION]... ARCHIVELOCATION %%f %%p %%r'\n"
"e.g.\n"
" restore_command = 'pg_standby -l /mnt/server/archiverdir %%f %%p %%r'\n");
printf("\nOptions:\n");
printf(" -c copies file from archive (default)\n");
printf(" -d generate lots of debugging output (testing only)\n");
printf(" -k NUMFILESTOKEEP if RESTARTWALFILE not used, removes files prior to limit\n"
" (0 keeps all)\n");
printf(" -l links into archive (leaves file in archive)\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 defines a trigger file to initiate failover (no default)\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(" --version output version information, then exit\n");
printf("\nReport bugs to <pgsql-bugs@postgresql.org>.\n");
}
static void
sighandler(int sig)
{
signaled = true;
}
#ifndef WIN32
/* We don't want SIGQUIT to core dump */
static void
sigquit_handler(int sig)
{
signal(SIGINT, SIG_DFL);
kill(getpid(), SIGINT);
}
#endif
/*------------ MAIN ----------------------------------------*/
int
main(int argc, char **argv)
{
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);
}
}
/*
* 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.
*/
(void) signal(SIGUSR1, sighandler);
(void) signal(SIGINT, sighandler); /* deprecated, use SIGUSR1 */
#ifndef WIN32
(void) signal(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 */
restoreCommandType = RESTORE_COMMAND_LINK;
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 = optarg;
if (CheckForExternalTrigger())
exit(1); /* Normal exit, with non-zero */
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: use %%f to specify nextWALFileName\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: use %%p to specify xlogFilePath\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, "\nTrigger file : %s", triggerPath ? triggerPath : "<not set>");
fprintf(stderr, "\nWaiting for WAL file : %s", nextWALFileName);
fprintf(stderr, "\nWAL file path : %s", WALFilePath);
fprintf(stderr, "\nRestoring to... : %s", xlogFilePath);
fprintf(stderr, "\nSleep interval : %d second%s",
sleeptime, (sleeptime > 1 ? "s" : " "));
fprintf(stderr, "\nMax wait interval : %d %s",
maxwaittime, (maxwaittime > 0 ? "seconds" : "forever"));
fprintf(stderr, "\nCommand for restore : %s", restoreCommand);
fprintf(stderr, "\nKeep archive history : ");
if (need_cleanup)
fprintf(stderr, "%s and later", exclusiveCleanupFileName);
else
fprintf(stderr, "No cleanup required");
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 (strlen(nextWALFileName) > 8 &&
strspn(nextWALFileName, "0123456789ABCDEF") == 8 &&
strcmp(nextWALFileName + strlen(nextWALFileName) - strlen(".history"),
".history") == 0)
{
nextWALFileType = XLOG_HISTORY;
if (RestoreWALFileForRecovery())
exit(0);
else
{
if (debug)
{
fprintf(stderr, "history file not found\n");
fflush(stderr);
}
exit(1);
}
}
/*
* Main wait loop
*/
while (!CustomizableNextWALFileReady() && !triggered)
{
if (sleeptime <= 60)
pg_usleep(sleeptime * 1000000L);
if (signaled)
{
triggered = true;
if (debug)
{
fprintf(stderr, "\nsignaled to exit\n");
fflush(stderr);
}
}
else
{
if (debug)
{
fprintf(stderr, "\nWAL file not present yet.");
if (triggerPath)
fprintf(stderr, " Checking for trigger file...");
fflush(stderr);
}
waittime += sleeptime;
if (!triggered && (CheckForExternalTrigger() || (waittime >= maxwaittime && maxwaittime > 0)))
{
triggered = true;
if (debug && waittime >= maxwaittime && maxwaittime > 0)
fprintf(stderr, "\nTimed out after %d seconds\n", waittime);
}
}
}
/*
* Action on exit
*/
if (triggered)
exit(1); /* Normal exit, with non-zero */
/*
* Once we have restored this file successfully we can remove some prior
* WAL files. If this restore fails we musn't remove any file because some
* of them will be requested again immediately after the failed restore,
* or when we restart recovery.
*/
if (RestoreWALFileForRecovery() && need_cleanup)
CustomizableCleanupPriorWALFiles();
return 0;
}