postgresql/contrib/pg_standby/pg_standby.c

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/*
* 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 "pg_config_manual.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;
/* 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;
bool 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 *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 inclusiveCleanupFileName[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-patches@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);
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, "pg_standby: archiveLocation \"%s\" does not exist\n", 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 reports that the file has the right number of bytes
* even though the file is still being copied and cannot be
* opened by pg_standby yet. So we wait for sleeptime secs
* before attempting to restore. If that is not enough, we
* will rely on the retry/holdoff mechanism.
*/
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)
{
uint32 tli,
log,
seg;
int signed_log = 0;
if (keepfiles > 0)
{
sscanf(nextWALFileName, "%08X%08X%08X", &tli, &log, &seg);
signed_log = log - (keepfiles / MaxSegmentsPerLogFile);
if (keepfiles <= seg)
seg -= keepfiles;
else
{
seg = MaxSegmentsPerLogFile - (keepfiles % MaxSegmentsPerLogFile);
signed_log--;
}
log = (uint32) signed_log;
}
/*
* Work out name of prior file from current filename
*/
if (keepfiles > 0 && signed_log >= 0 && nextWALFileType == XLOG_DATA)
{
int rc;
DIR *xldir;
struct dirent *xlde;
XLogFileName(inclusiveCleanupFileName, tli, log, seg);
/*
* 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 inclusiveCleanupFileName file.
*/
if (strlen(xlde->d_name) == XLOG_DATA_FNAME_LEN &&
strspn(xlde->d_name, "0123456789ABCDEF") == XLOG_DATA_FNAME_LEN &&
strcmp(xlde->d_name + 8, inclusiveCleanupFileName + 8) <= 0)
{
#ifdef WIN32
snprintf(WALFilePath, MAXPGPATH, "%s\\%s", archiveLocation, xlde->d_name);
#else
snprintf(WALFilePath, MAXPGPATH, "%s/%s", archiveLocation, xlde->d_name);
#endif
rc = unlink(WALFilePath);
if (debug)
fprintf(stderr, "\npg_standby: removed \"%s\"\n", WALFilePath);
}
}
}
else
fprintf(stderr, "pg_standby: archiveLocation \"%s\" open error\n", archiveLocation);
closedir(xldir);
}
fflush(stderr);
}
/* =====================================================================
* End of Customizable section
* =====================================================================
*/
/*
* 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: unable to remove \"%s\", rc=%d", triggerPath, rc);
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, " success\n");
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()
{
fprintf(stderr, "\npg_standby allows Warm Standby servers to be configured\n");
fprintf(stderr, "Usage:\n");
fprintf(stderr, " pg_standby [OPTION]... [ARCHIVELOCATION] [NEXTWALFILE] [XLOGFILEPATH]\n");
fprintf(stderr, " note space between [ARCHIVELOCATION] and [NEXTWALFILE]\n");
fprintf(stderr, "with main intended use via restore_command in the recovery.conf\n");
fprintf(stderr, " restore_command = 'pg_standby [OPTION]... [ARCHIVELOCATION] %%f %%p'\n");
fprintf(stderr, "e.g. restore_command = 'pg_standby -l -u /mnt/server/archiverdir %%f %%p'\n");
fprintf(stderr, "\nOptions:\n");
fprintf(stderr, " -c copies file from archive (default)\n");
fprintf(stderr, " -d generate lots of debugging output (testing only)\n");
fprintf(stderr, " -k [NUMFILESTOKEEP] keeps history of # files in archives; unlinks/removes files beyond that\n");
fprintf(stderr, " -l links into archive (leaves file in archive)\n");
fprintf(stderr, " -t [TRIGGERFILE] defines a trigger file to initiate failover (no default)\n");
fprintf(stderr, " -r [MAXRETRIES] maximum number of times to retry, with progressive wait (default=3)\n");
fprintf(stderr, " -s [SLEEPTIME] number of seconds to wait between file checks (default=5)\n");
fprintf(stderr, " -w [MAXWAITTIME] max number of seconds to wait for a file (0 disables)(default=0)\n");
fflush(stderr);
}
static void
sighandler(int sig)
{
triggered = true;
signaled = true;
}
/*------------ MAIN ----------------------------------------*/
int
main(int argc, char **argv)
{
int c;
(void) signal(SIGINT, sighandler);
(void) signal(SIGQUIT, sighandler);
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, "usage: pg_standby -k keepfiles must be > 0\n");
usage();
exit(2);
}
break;
case 'l': /* Use link */
restoreCommandType = RESTORE_COMMAND_LINK;
break;
case 'r': /* Retries */
maxretries = atoi(optarg);
if (maxretries < 0)
{
fprintf(stderr, "usage: pg_standby -r maxretries must be > 0\n");
usage();
exit(2);
}
break;
case 's': /* Sleep time */
sleeptime = atoi(optarg);
if (sleeptime <= 0 || sleeptime > 60)
{
fprintf(stderr, "usage: pg_standby -s sleeptime incorrectly set\n");
usage();
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, "usage: pg_standby -w maxwaittime incorrectly set\n");
usage();
exit(2);
}
break;
default:
usage();
exit(2);
break;
}
}
/*
* Parameter checking - after checking to see if trigger file present
*/
if (argc == 1)
{
usage();
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, "pg_standby: must specify archiveLocation\n");
usage();
exit(2);
}
if (optind < argc)
{
nextWALFileName = argv[optind];
optind++;
}
else
{
fprintf(stderr, "pg_standby: use %%f to specify nextWALFileName\n");
usage();
exit(2);
}
if (optind < argc)
{
xlogFilePath = argv[optind];
optind++;
}
else
{
fprintf(stderr, "pg_standby: use %%p to specify xlogFilePath\n");
usage();
exit(2);
}
CustomizableInitialize();
if (debug)
{
fprintf(stderr, "\nTrigger file : %s", triggerPath ? triggerPath : "<not set>");
fprintf(stderr, "\nWaiting for WAL file : %s", WALFilePath);
fprintf(stderr, "\nWAL file path : %s", nextWALFileName);
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);
if (keepfiles > 0)
fprintf(stderr, "\nNum archived files kept : last %d files", keepfiles);
else
fprintf(stderr, "\nNum archived files kept : all files");
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)
{
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 */
else
{
/*
* 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())
CustomizableCleanupPriorWALFiles();
exit(0);
}
}