mirror of
https://git.postgresql.org/git/postgresql.git
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624 lines
16 KiB
C
624 lines
16 KiB
C
/*
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* pg_standby.c
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*
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* Production-ready example of how to create a Warm Standby
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* database server using continuous archiving as a
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* replication mechanism
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*
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* We separate the parameters for archive and nextWALfile
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* so that we can check the archive exists, even if the
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* WAL file doesn't (yet).
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*
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* This program will be executed once in full for each file
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* requested by the warm standby server.
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*
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* It is designed to cater to a variety of needs, as well
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* providing a customizable section.
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*
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* Original author: Simon Riggs simon@2ndquadrant.com
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* Current maintainer: Simon Riggs
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*/
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#include "postgres_fe.h"
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#include "pg_config_manual.h"
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#include <ctype.h>
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#include <dirent.h>
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#include <sys/stat.h>
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#include <signal.h>
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#ifdef WIN32
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int getopt(int argc, char * const argv[], const char *optstring);
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#else
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#include <sys/time.h>
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#include <unistd.h>
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#ifdef HAVE_GETOPT_H
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#include <getopt.h>
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#endif
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#endif /* ! WIN32 */
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extern char *optarg;
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extern int optind;
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/* Options and defaults */
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int sleeptime = 5; /* amount of time to sleep between file checks */
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int waittime = -1; /* how long we have been waiting, -1 no wait yet */
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int maxwaittime = 0; /* how long are we prepared to wait for? */
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int keepfiles = 0; /* number of WAL files to keep, 0 keep all */
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int maxretries = 3; /* number of retries on restore command */
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bool debug = false; /* are we debugging? */
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bool triggered = false;
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bool signaled = false;
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char *archiveLocation; /* where to find the archive? */
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char *triggerPath; /* where to find the trigger file? */
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char *xlogFilePath; /* where we are going to restore to */
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char *nextWALFileName; /* the file we need to get from archive */
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char *priorWALFileName; /* the file we need to get from archive */
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char WALFilePath[MAXPGPATH];/* the file path including archive */
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char restoreCommand[MAXPGPATH]; /* run this to restore */
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char inclusiveCleanupFileName[MAXPGPATH]; /* the file we need to get from archive */
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#define RESTORE_COMMAND_COPY 0
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#define RESTORE_COMMAND_LINK 1
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int restoreCommandType;
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#define XLOG_DATA 0
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#define XLOG_HISTORY 1
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#define XLOG_BACKUP_LABEL 2
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int nextWALFileType;
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#define SET_RESTORE_COMMAND(cmd, arg1, arg2) \
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snprintf(restoreCommand, MAXPGPATH, cmd " %s %s", arg1, arg2)
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struct stat stat_buf;
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/* =====================================================================
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*
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* Customizable section
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*
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* =====================================================================
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*
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* Currently, this section assumes that the Archive is a locally
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* accessible directory. If you want to make other assumptions,
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* such as using a vendor-specific archive and access API, these
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* routines are the ones you'll need to change. You're
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* enouraged to submit any changes to pgsql-patches@postgresql.org
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* or personally to the current maintainer. Those changes may be
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* folded in to later versions of this program.
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*/
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#define XLOG_DATA_FNAME_LEN 24
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/* Reworked from access/xlog_internal.h */
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#define XLogFileName(fname, tli, log, seg) \
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snprintf(fname, XLOG_DATA_FNAME_LEN + 1, "%08X%08X%08X", tli, log, seg)
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/*
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* Initialize allows customized commands into the warm standby program.
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*
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* As an example, and probably the common case, we use either
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* cp/ln commands on *nix, or copy/move command on Windows.
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*
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*/
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static void
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CustomizableInitialize(void)
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{
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#ifdef WIN32
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snprintf(WALFilePath, MAXPGPATH, "%s\\%s", archiveLocation, nextWALFileName);
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switch (restoreCommandType)
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{
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case RESTORE_COMMAND_LINK:
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SET_RESTORE_COMMAND("mklink",WALFilePath, xlogFilePath);
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case RESTORE_COMMAND_COPY:
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default:
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SET_RESTORE_COMMAND("copy",WALFilePath, xlogFilePath);
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break;
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}
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#else
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snprintf(WALFilePath, MAXPGPATH, "%s/%s", archiveLocation, nextWALFileName);
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switch (restoreCommandType)
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{
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case RESTORE_COMMAND_LINK:
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#if HAVE_WORKING_LINK
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SET_RESTORE_COMMAND("ln -s -f",WALFilePath, xlogFilePath);
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break;
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#endif
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case RESTORE_COMMAND_COPY:
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default:
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SET_RESTORE_COMMAND("cp",WALFilePath, xlogFilePath);
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break;
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}
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#endif
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/*
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* This code assumes that archiveLocation is a directory
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* You may wish to add code to check for tape libraries, etc..
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* So, since it is a directory, we use stat to test if its accessible
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*/
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if (stat(archiveLocation, &stat_buf) != 0)
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{
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fprintf(stderr, "pg_standby: archiveLocation \"%s\" does not exist\n", archiveLocation);
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fflush(stderr);
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exit(2);
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}
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}
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/*
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* CustomizableNextWALFileReady()
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*
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* Is the requested file ready yet?
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*/
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static bool
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CustomizableNextWALFileReady()
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{
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if (stat(WALFilePath, &stat_buf) == 0)
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{
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/*
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* If its a backup file, return immediately
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* If its a regular file return only if its the right size already
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*/
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if (strlen(nextWALFileName) > 24 &&
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strspn(nextWALFileName, "0123456789ABCDEF") == 24 &&
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strcmp(nextWALFileName + strlen(nextWALFileName) - strlen(".backup"),
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".backup") == 0)
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{
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nextWALFileType = XLOG_BACKUP_LABEL;
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return true;
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}
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else
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if (stat_buf.st_size == XLOG_SEG_SIZE)
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{
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#ifdef WIN32
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/*
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* Windows reports that the file has the right number of bytes
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* even though the file is still being copied and cannot be
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* opened by pg_standby yet. So we wait for sleeptime secs
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* before attempting to restore. If that is not enough, we
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* will rely on the retry/holdoff mechanism.
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*/
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pg_usleep(sleeptime * 1000000L);
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#endif
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nextWALFileType = XLOG_DATA;
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return true;
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}
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/*
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* If still too small, wait until it is the correct size
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*/
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if (stat_buf.st_size > XLOG_SEG_SIZE)
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{
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if (debug)
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{
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fprintf(stderr, "file size greater than expected\n");
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fflush(stderr);
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}
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exit(3);
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}
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}
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return false;
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}
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#define MaxSegmentsPerLogFile ( 0xFFFFFFFF / XLOG_SEG_SIZE )
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static void
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CustomizableCleanupPriorWALFiles(void)
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{
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uint32 tli,
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log,
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seg;
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int signed_log = 0;
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if (keepfiles > 0)
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{
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sscanf(nextWALFileName, "%08X%08X%08X", &tli, &log, &seg);
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signed_log = log - (keepfiles / MaxSegmentsPerLogFile);
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if (keepfiles <= seg)
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seg -= keepfiles;
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else
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{
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seg = MaxSegmentsPerLogFile - (keepfiles % MaxSegmentsPerLogFile);
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signed_log--;
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}
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log = (uint32) signed_log;
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}
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/*
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* Work out name of prior file from current filename
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*/
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if (keepfiles > 0 && signed_log >= 0 && nextWALFileType == XLOG_DATA)
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{
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int rc;
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DIR *xldir;
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struct dirent *xlde;
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XLogFileName(inclusiveCleanupFileName, tli, log, seg);
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/*
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* Assume its OK to keep failing. The failure situation may change over
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* time, so we'd rather keep going on the main processing than fail
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* because we couldnt clean up yet.
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*/
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if ((xldir = opendir(archiveLocation)) != NULL)
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{
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while ((xlde = readdir(xldir)) != NULL)
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{
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/*
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* We ignore the timeline part of the XLOG segment identifiers in
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* deciding whether a segment is still needed. This ensures that we
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* won't prematurely remove a segment from a parent timeline. We could
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* probably be a little more proactive about removing segments of
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* non-parent timelines, but that would be a whole lot more
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* complicated.
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*
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* We use the alphanumeric sorting property of the filenames to decide
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* which ones are earlier than the inclusiveCleanupFileName file.
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*/
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if (strlen(xlde->d_name) == XLOG_DATA_FNAME_LEN &&
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strspn(xlde->d_name, "0123456789ABCDEF") == XLOG_DATA_FNAME_LEN &&
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strcmp(xlde->d_name + 8, inclusiveCleanupFileName + 8) <= 0)
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{
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#ifdef WIN32
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snprintf(WALFilePath, MAXPGPATH, "%s\\%s", archiveLocation, xlde->d_name);
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#else
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snprintf(WALFilePath, MAXPGPATH, "%s/%s", archiveLocation, xlde->d_name);
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#endif
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if (debug)
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fprintf(stderr, "\npg_standby: removing \"%s\"\n", WALFilePath);
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rc = unlink(WALFilePath);
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if (rc !=0 )
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fprintf(stderr, "\npg_standby: ERROR failed to remove \"%s\" because %s\n", WALFilePath, strerror(errno));
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}
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}
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}
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else
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fprintf(stderr, "pg_standby: archiveLocation \"%s\" open error\n", archiveLocation);
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closedir(xldir);
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}
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fflush(stderr);
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}
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/* =====================================================================
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* End of Customizable section
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* =====================================================================
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*/
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/*
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* CheckForExternalTrigger()
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*
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* Is there a trigger file?
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*/
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static bool
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CheckForExternalTrigger(void)
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{
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int rc;
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/*
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* Look for a trigger file, if that option has been selected
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*
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* We use stat() here because triggerPath is always a file
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* rather than potentially being in an archive
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*/
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if (triggerPath && stat(triggerPath, &stat_buf) == 0)
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{
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fprintf(stderr, "trigger file found\n");
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fflush(stderr);
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/*
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* If trigger file found, we *must* delete it. Here's why:
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* When recovery completes, we will be asked again
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* for the same file from the archive using pg_standby
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* so must remove trigger file so we can reload file again
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* and come up correctly.
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*/
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rc = unlink(triggerPath);
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if (rc != 0)
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{
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fprintf(stderr, "\n ERROR: unable to remove \"%s\", because %s", triggerPath, strerror(errno));
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fflush(stderr);
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exit(rc);
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}
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return true;
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}
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return false;
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}
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/*
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* RestoreWALFileForRecovery()
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*
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* Perform the action required to restore the file from archive
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*/
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static bool
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RestoreWALFileForRecovery(void)
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{
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int rc = 0;
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int numretries = 0;
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if (debug)
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{
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fprintf(stderr, "\nrunning restore :");
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fflush(stderr);
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}
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while (numretries < maxretries)
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{
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rc = system(restoreCommand);
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if (rc == 0)
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{
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if (debug)
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{
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fprintf(stderr, " success\n");
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fflush(stderr);
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}
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return true;
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}
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pg_usleep(numretries++ * sleeptime * 1000000L);
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}
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/*
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* Allow caller to add additional info
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*/
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if (debug)
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fprintf(stderr, "not restored : ");
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return false;
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}
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static void
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usage()
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{
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fprintf(stderr, "\npg_standby allows Warm Standby servers to be configured\n");
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fprintf(stderr, "Usage:\n");
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fprintf(stderr, " pg_standby [OPTION]... [ARCHIVELOCATION] [NEXTWALFILE] [XLOGFILEPATH]\n");
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fprintf(stderr, " note space between [ARCHIVELOCATION] and [NEXTWALFILE]\n");
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fprintf(stderr, "with main intended use via restore_command in the recovery.conf\n");
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fprintf(stderr, " restore_command = 'pg_standby [OPTION]... [ARCHIVELOCATION] %%f %%p'\n");
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fprintf(stderr, "e.g. restore_command = 'pg_standby -l -u /mnt/server/archiverdir %%f %%p'\n");
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fprintf(stderr, "\nOptions:\n");
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fprintf(stderr, " -c copies file from archive (default)\n");
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fprintf(stderr, " -d generate lots of debugging output (testing only)\n");
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fprintf(stderr, " -k [NUMFILESTOKEEP] keeps history of # files in archives; unlinks/removes files beyond that\n");
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fprintf(stderr, " -l links into archive (leaves file in archive)\n");
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fprintf(stderr, " -t [TRIGGERFILE] defines a trigger file to initiate failover (no default)\n");
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fprintf(stderr, " -r [MAXRETRIES] maximum number of times to retry, with progressive wait (default=3)\n");
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fprintf(stderr, " -s [SLEEPTIME] number of seconds to wait between file checks (default=5)\n");
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fprintf(stderr, " -w [MAXWAITTIME] max number of seconds to wait for a file (0 disables)(default=0)\n");
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fflush(stderr);
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}
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static void
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sighandler(int sig)
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{
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triggered = true;
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signaled = true;
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}
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/*------------ MAIN ----------------------------------------*/
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int
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main(int argc, char **argv)
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{
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int c;
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(void) signal(SIGINT, sighandler);
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(void) signal(SIGQUIT, sighandler);
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while ((c = getopt(argc, argv, "cdk:lr:s:t:w:")) != -1)
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{
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switch (c)
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{
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case 'c': /* Use copy */
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restoreCommandType = RESTORE_COMMAND_COPY;
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break;
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case 'd': /* Debug mode */
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debug = true;
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break;
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case 'k': /* keepfiles */
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keepfiles = atoi(optarg);
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if (keepfiles <= 0)
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{
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fprintf(stderr, "usage: pg_standby -k keepfiles must be > 0\n");
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usage();
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exit(2);
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}
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break;
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case 'l': /* Use link */
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restoreCommandType = RESTORE_COMMAND_LINK;
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break;
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case 'r': /* Retries */
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maxretries = atoi(optarg);
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if (maxretries < 0)
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{
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fprintf(stderr, "usage: pg_standby -r maxretries must be > 0\n");
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usage();
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exit(2);
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}
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break;
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case 's': /* Sleep time */
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sleeptime = atoi(optarg);
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if (sleeptime <= 0 || sleeptime > 60)
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{
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fprintf(stderr, "usage: pg_standby -s sleeptime incorrectly set\n");
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usage();
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exit(2);
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}
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break;
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case 't': /* Trigger file */
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triggerPath = optarg;
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if (CheckForExternalTrigger())
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exit(1); /* Normal exit, with non-zero */
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break;
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case 'w': /* Max wait time */
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maxwaittime = atoi(optarg);
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if (maxwaittime < 0)
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{
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fprintf(stderr, "usage: pg_standby -w maxwaittime incorrectly set\n");
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usage();
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exit(2);
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}
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break;
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default:
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usage();
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exit(2);
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break;
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}
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}
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/*
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* Parameter checking - after checking to see if trigger file present
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*/
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if (argc == 1)
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{
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usage();
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exit(2);
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}
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/*
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* We will go to the archiveLocation to get nextWALFileName.
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* nextWALFileName may not exist yet, which would not be an error,
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* so we separate the archiveLocation and nextWALFileName so we can check
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* separately whether archiveLocation exists, if not that is an error
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*/
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if (optind < argc)
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{
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archiveLocation = argv[optind];
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optind++;
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}
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else
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{
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fprintf(stderr, "pg_standby: must specify archiveLocation\n");
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usage();
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exit(2);
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}
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if (optind < argc)
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{
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nextWALFileName = argv[optind];
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optind++;
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}
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else
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{
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fprintf(stderr, "pg_standby: use %%f to specify nextWALFileName\n");
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usage();
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exit(2);
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}
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if (optind < argc)
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{
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xlogFilePath = argv[optind];
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optind++;
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}
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else
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{
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fprintf(stderr, "pg_standby: use %%p to specify xlogFilePath\n");
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usage();
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exit(2);
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}
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CustomizableInitialize();
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if (debug)
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{
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fprintf(stderr, "\nTrigger file : %s", triggerPath ? triggerPath : "<not set>");
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fprintf(stderr, "\nWaiting for WAL file : %s", WALFilePath);
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fprintf(stderr, "\nWAL file path : %s", nextWALFileName);
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fprintf(stderr, "\nRestoring to... : %s", xlogFilePath);
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fprintf(stderr, "\nSleep interval : %d second%s",
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sleeptime, (sleeptime > 1 ? "s" : " "));
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fprintf(stderr, "\nMax wait interval : %d %s",
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maxwaittime, (maxwaittime > 0 ? "seconds" : "forever"));
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fprintf(stderr, "\nCommand for restore : %s", restoreCommand);
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if (keepfiles > 0)
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fprintf(stderr, "\nNum archived files kept : last %d files", keepfiles);
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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);
|
|
}
|
|
}
|