archive.c

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/*-------------------------------------------------------------------------
 *
 * archive.c
 *    Routines to access WAL archives from frontend
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/fe_utils/archive.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres_fe.h"
 
#include <unistd.h>
#include <sys/stat.h>
 
#include "access/xlog_internal.h"
#include "common/archive.h"
#include "common/logging.h"
#include "fe_utils/archive.h"
 
 
/*
 * RestoreArchivedFile
 *
 * Attempt to retrieve the specified file from off-line archival storage.
 * If successful, return a file descriptor of the restored file, else
 * return -1.
 *
 * For fixed-size files, the caller may pass the expected size as an
 * additional crosscheck on successful recovery.  If the file size is not
 * known, set expectedSize = 0.
 */
int
RestoreArchivedFile(const char *path, const char *xlogfname,
                    off_t expectedSize, const char *restoreCommand)
{
    char        xlogpath[MAXPGPATH];
    char       *xlogRestoreCmd;
    int         rc;
    struct stat stat_buf;
 
    snprintf(xlogpath, MAXPGPATH, "%s/" XLOGDIR "/%s", path, xlogfname);
 
    xlogRestoreCmd = BuildRestoreCommand(restoreCommand, xlogpath,
                                         xlogfname, NULL);
 
    /*
     * Execute restore_command, which should copy the missing file from
     * archival storage.
     */
    fflush(NULL);
    rc = system(xlogRestoreCmd);
    pfree(xlogRestoreCmd);
 
    if (rc == 0)
    {
        /*
         * Command apparently succeeded, but let's make sure the file is
         * really there now and has the correct size.
         */
        if (stat(xlogpath, &stat_buf) == 0)
        {
            if (expectedSize > 0 && stat_buf.st_size != expectedSize)
                pg_fatal("unexpected file size for \"%s\": %lld instead of %lld",
                         xlogfname, (long long int) stat_buf.st_size,
                         (long long int) expectedSize);
            else
            {
                int         xlogfd = open(xlogpath, O_RDONLY | PG_BINARY, 0);
 
                if (xlogfd < 0)
                    pg_fatal("could not open file \"%s\" restored from archive: %m",
                             xlogpath);
                else
                    return xlogfd;
            }
        }
        else
        {
            if (errno != ENOENT)
                pg_fatal("could not stat file \"%s\": %m",
                         xlogpath);
        }
    }
 
    /*
     * If the failure was due to a signal, then it would be misleading to
     * return with a failure at restoring the file.  So just bail out and
     * exit.  Hard shell errors such as "command not found" are treated as
     * fatal too.
     */
    if (wait_result_is_any_signal(rc, true))
        pg_fatal("\"restore_command\" failed: %s",
                 wait_result_to_str(rc));
 
    /*
     * The file is not available, so just let the caller decide what to do
     * next.
     */
    pg_log_error("could not restore file \"%s\" from archive",
                 xlogfname);
    return -1;
}