shell_archive.c

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/*-------------------------------------------------------------------------
 *
 * shell_archive.c
 *
 * This archiving function uses a user-specified shell command (the
 * archive_command GUC) to copy write-ahead log files.  It is used as the
 * default, but other modules may define their own custom archiving logic.
 *
 * Copyright (c) 2022-2025, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/archive/shell_archive.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include <sys/wait.h>
 
#include "access/xlog.h"
#include "archive/archive_module.h"
#include "archive/shell_archive.h"
#include "common/percentrepl.h"
#include "pgstat.h"
 
static bool shell_archive_configured(ArchiveModuleState *state);
static bool shell_archive_file(ArchiveModuleState *state,
                               const char *file,
                               const char *path);
static void shell_archive_shutdown(ArchiveModuleState *state);
 
static const ArchiveModuleCallbacks shell_archive_callbacks = {
    .startup_cb = NULL,
    .check_configured_cb = shell_archive_configured,
    .archive_file_cb = shell_archive_file,
    .shutdown_cb = shell_archive_shutdown
};
 
const ArchiveModuleCallbacks *
shell_archive_init(void)
{
    return &shell_archive_callbacks;
}
 
static bool
shell_archive_configured(ArchiveModuleState *state)
{
    if (XLogArchiveCommand[0] != '\0')
        return true;
 
    arch_module_check_errdetail("\"%s\" is not set.",
                                "archive_command");
    return false;
}
 
static bool
shell_archive_file(ArchiveModuleState *state, const char *file,
                   const char *path)
{
    char       *xlogarchcmd;
    char       *nativePath = NULL;
    int         rc;
 
    if (path)
    {
        nativePath = pstrdup(path);
        make_native_path(nativePath);
    }
 
    xlogarchcmd = replace_percent_placeholders(XLogArchiveCommand,
                                               "archive_command", "fp",
                                               file, nativePath);
 
    ereport(DEBUG3,
            (errmsg_internal("executing archive command \"%s\"",
                             xlogarchcmd)));
 
    fflush(NULL);
    pgstat_report_wait_start(WAIT_EVENT_ARCHIVE_COMMAND);
    rc = system(xlogarchcmd);
    pgstat_report_wait_end();
 
    if (rc != 0)
    {
        /*
         * If either the shell itself, or a called command, died on a signal,
         * abort the archiver.  We do this because system() ignores SIGINT and
         * SIGQUIT while waiting; so a signal is very likely something that
         * should have interrupted us too.  Also die if the shell got a hard
         * "command not found" type of error.  If we overreact it's no big
         * deal, the postmaster will just start the archiver again.
         */
        int         lev = wait_result_is_any_signal(rc, true) ? FATAL : LOG;
 
        if (WIFEXITED(rc))
        {
            ereport(lev,
                    (errmsg("archive command failed with exit code %d",
                            WEXITSTATUS(rc)),
                     errdetail("The failed archive command was: %s",
                               xlogarchcmd)));
        }
        else if (WIFSIGNALED(rc))
        {
#if defined(WIN32)
            ereport(lev,
                    (errmsg("archive command was terminated by exception 0x%X",
                            WTERMSIG(rc)),
                     errhint("See C include file \"ntstatus.h\" for a description of the hexadecimal value."),
                     errdetail("The failed archive command was: %s",
                               xlogarchcmd)));
#else
            ereport(lev,
                    (errmsg("archive command was terminated by signal %d: %s",
                            WTERMSIG(rc), pg_strsignal(WTERMSIG(rc))),
                     errdetail("The failed archive command was: %s",
                               xlogarchcmd)));
#endif
        }
        else
        {
            ereport(lev,
                    (errmsg("archive command exited with unrecognized status %d",
                            rc),
                     errdetail("The failed archive command was: %s",
                               xlogarchcmd)));
        }
        pfree(xlogarchcmd);
 
        return false;
    }
    pfree(xlogarchcmd);
 
    elog(DEBUG1, "archived write-ahead log file \"%s\"", file);
    return true;
}
 
static void
shell_archive_shutdown(ArchiveModuleState *state)
{
    elog(DEBUG1, "archiver process shutting down");
}