postgres/src/backend/postmaster/shell_archive.c

/*-------------------------------------------------------------------------
 *
 * 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, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *	  src/backend/postmaster/shell_archive.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <sys/wait.h>

#include "access/xlog.h"
#include "pgstat.h"
#include "postmaster/pgarch.h"

static bool shell_archive_configured(void);
static bool shell_archive_file(const char *file, const char *path);

void
shell_archive_init(ArchiveModuleCallbacks *cb)
{
	AssertVariableIsOfType(&shell_archive_init, ArchiveModuleInit);

	cb->check_configured_cb = shell_archive_configured;
	cb->archive_file_cb = shell_archive_file;
}

static bool
shell_archive_configured(void)
{
	return XLogArchiveCommand[0] != '\0';
}

static bool
shell_archive_file(const char *file, const char *path)
{
	char		xlogarchcmd[MAXPGPATH];
	char	   *dp;
	char	   *endp;
	const char *sp;
	int			rc;

	/*
	 * construct the command to be executed
	 */
	dp = xlogarchcmd;
	endp = xlogarchcmd + MAXPGPATH - 1;
	*endp = '\0';

	for (sp = XLogArchiveCommand; *sp; sp++)
	{
		if (*sp == '%')
		{
			switch (sp[1])
			{
				case 'p':
					/* %p: relative path of source file */
					sp++;
					strlcpy(dp, path, endp - dp);
					make_native_path(dp);
					dp += strlen(dp);
					break;
				case 'f':
					/* %f: filename of source file */
					sp++;
					strlcpy(dp, file, endp - dp);
					dp += strlen(dp);
					break;
				case '%':
					/* convert %% to a single % */
					sp++;
					if (dp < endp)
						*dp++ = *sp;
					break;
				default:
					/* otherwise treat the % as not special */
					if (dp < endp)
						*dp++ = *sp;
					break;
			}
		}
		else
		{
			if (dp < endp)
				*dp++ = *sp;
		}
	}
	*dp = '\0';

	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)));
		}

		return false;
	}

	elog(DEBUG1, "archived write-ahead log file \"%s\"", file);
	return true;
}