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7fed801135
More than twenty years ago (79fcde48b), we hacked the postmaster
to avoid a core-dump on systems that didn't support fflush(NULL).
We've mostly, though not completely, hewed to that rule ever since.
But such systems are surely gone in the wild, so in the spirit of
cleaning out no-longer-needed portability hacks let's get rid of
multiple per-file fflush() calls in favor of using fflush(NULL).
Also, we were fairly inconsistent about whether to fflush() before
popen() and system() calls. While we've received no bug reports
about that, it seems likely that at least some of these call sites
are at risk of odd behavior, such as error messages appearing in
an unexpected order. Rather than expend a lot of brain cells
figuring out which places are at hazard, let's just establish a
uniform coding rule that we should fflush(NULL) before these calls.
A no-op fflush() is surely of trivial cost compared to launching
a sub-process via a shell; while if it's not a no-op then we likely
need it.
Discussion: https://postgr.es/m/2923412.1661722825@sss.pgh.pa.us
111 lines
2.8 KiB
C
111 lines
2.8 KiB
C
/*-------------------------------------------------------------------------
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*
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* archive.c
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* Routines to access WAL archives from frontend
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*
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* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/fe_utils/archive.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres_fe.h"
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#include <unistd.h>
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#include <sys/stat.h>
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#include "access/xlog_internal.h"
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#include "common/archive.h"
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#include "common/logging.h"
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#include "fe_utils/archive.h"
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/*
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* RestoreArchivedFile
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*
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* Attempt to retrieve the specified file from off-line archival storage.
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* If successful, return a file descriptor of the restored file, else
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* return -1.
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*
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* For fixed-size files, the caller may pass the expected size as an
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* additional crosscheck on successful recovery. If the file size is not
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* known, set expectedSize = 0.
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*/
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int
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RestoreArchivedFile(const char *path, const char *xlogfname,
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off_t expectedSize, const char *restoreCommand)
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{
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char xlogpath[MAXPGPATH];
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char *xlogRestoreCmd;
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int rc;
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struct stat stat_buf;
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snprintf(xlogpath, MAXPGPATH, "%s/" XLOGDIR "/%s", path, xlogfname);
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xlogRestoreCmd = BuildRestoreCommand(restoreCommand, xlogpath,
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xlogfname, NULL);
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if (xlogRestoreCmd == NULL)
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pg_fatal("cannot use restore_command with %%r placeholder");
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/*
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* Execute restore_command, which should copy the missing file from
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* archival storage.
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*/
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fflush(NULL);
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rc = system(xlogRestoreCmd);
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pfree(xlogRestoreCmd);
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if (rc == 0)
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{
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/*
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* Command apparently succeeded, but let's make sure the file is
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* really there now and has the correct size.
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*/
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if (stat(xlogpath, &stat_buf) == 0)
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{
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if (expectedSize > 0 && stat_buf.st_size != expectedSize)
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pg_fatal("unexpected file size for \"%s\": %lld instead of %lld",
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xlogfname, (long long int) stat_buf.st_size,
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(long long int) expectedSize);
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else
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{
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int xlogfd = open(xlogpath, O_RDONLY | PG_BINARY, 0);
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if (xlogfd < 0)
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pg_fatal("could not open file \"%s\" restored from archive: %m",
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xlogpath);
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else
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return xlogfd;
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}
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}
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else
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{
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if (errno != ENOENT)
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pg_fatal("could not stat file \"%s\": %m",
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xlogpath);
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}
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}
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/*
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* If the failure was due to a signal, then it would be misleading to
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* return with a failure at restoring the file. So just bail out and
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* exit. Hard shell errors such as "command not found" are treated as
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* fatal too.
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*/
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if (wait_result_is_any_signal(rc, true))
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pg_fatal("restore_command failed: %s",
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wait_result_to_str(rc));
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/*
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* The file is not available, so just let the caller decide what to do
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* next.
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*/
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pg_log_error("could not restore file \"%s\" from archive",
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xlogfname);
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return -1;
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}
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