Prevent shutdown in normal mode if online backup is running, and

have pg_ctl warn about this.

Cancel running online backups (by renaming the backup_label file,
thus rendering the backup useless) when shutting down in fast mode.

Laurenz Albe

4 files changed, 105 insertions, 8 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 33c912ebaa4..d23fc9b5614 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.298 2008/04/21 00:26:44 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.299 2008/04/23 13:44:58 mha Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -6577,6 +6577,7 @@ pg_start_backup_callback(int code, Datum arg)
  * create a backup history file in pg_xlog (whence it will immediately be
  * archived).  The backup history file contains the same info found in
  * the label file, plus the backup-end time and WAL location.
+ * Note: different from CancelBackup which just cancels online backup mode.
  */
 Datum
 pg_stop_backup(PG_FUNCTION_ARGS)
@@ -7063,3 +7064,52 @@ rm_redo_error_callback(void *arg)
 
 	pfree(buf.data);
 }
+
+/*
+ * BackupInProgress: check if online backup mode is active
+ *
+ * This is done by checking for existence of the "backup_label" file.
+ */
+bool
+BackupInProgress(void)
+{
+	struct stat stat_buf;
+
+	return (stat(BACKUP_LABEL_FILE, &stat_buf) == 0);
+}
+
+/*
+ * CancelBackup: rename the "backup_label" file to cancel backup mode
+ *
+ * If the "backup_label" file exists, it will be renamed to "backup_label.old".
+ * Note that this will render an online backup in progress useless.
+ * To correctly finish an online backup, pg_stop_backup must be called.
+ */
+void
+CancelBackup(void)
+{
+	struct stat stat_buf;
+
+	/* if the file is not there, return */
+	if (stat(BACKUP_LABEL_FILE, &stat_buf) < 0)
+		return;
+
+	/* remove leftover file from previously cancelled backup if it exists */
+	unlink(BACKUP_LABEL_OLD);
+
+	if (rename(BACKUP_LABEL_FILE, BACKUP_LABEL_OLD) == 0)
+	{
+		ereport(LOG,
+				(errmsg("online backup mode cancelled"),
+				 errdetail("\"%s\" renamed to \"%s\"",
+						BACKUP_LABEL_FILE, BACKUP_LABEL_OLD)));
+	}
+	else
+	{
+		ereport(WARNING,
+				(errcode_for_file_access(),
+				 errmsg("could not rename \"%s\" to \"%s\", backup mode not cancelled: %m",
+						BACKUP_LABEL_FILE, BACKUP_LABEL_OLD)));
+	}
+}
+
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 7c6692b2a5d..f3bcdd968c7 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.554 2008/03/31 02:43:14 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.555 2008/04/23 13:44:59 mha Exp $
  *
  * NOTES
  *
@@ -253,6 +253,7 @@ typedef enum
 	PM_INIT,					/* postmaster starting */
 	PM_STARTUP,					/* waiting for startup subprocess */
 	PM_RUN,						/* normal "database is alive" state */
+	PM_WAIT_BACKUP,				/* waiting for online backup mode to end */
 	PM_WAIT_BACKENDS,			/* waiting for live backends to exit */
 	PM_SHUTDOWN,				/* waiting for bgwriter to do shutdown ckpt */
 	PM_SHUTDOWN_2,				/* waiting for archiver to finish */
@@ -1724,8 +1725,12 @@ processCancelRequest(Port *port, void *pkt)
 static enum CAC_state
 canAcceptConnections(void)
 {
-	/* Can't start backends when in startup/shutdown/recovery state. */
-	if (pmState != PM_RUN)
+	/*
+	 * Can't start backends when in startup/shutdown/recovery state.
+	 * In state PM_WAIT_BACKUP we must allow connections so that
+	 * a superuser can end online backup mode.
+	 */
+	if ((pmState != PM_RUN) && (pmState != PM_WAIT_BACKUP))
 	{
 		if (Shutdown > NoShutdown)
 			return CAC_SHUTDOWN;	/* shutdown is pending */
@@ -1965,11 +1970,12 @@ pmdie(SIGNAL_ARGS)
 				/* and the walwriter too */
 				if (WalWriterPID != 0)
 					signal_child(WalWriterPID, SIGTERM);
-				pmState = PM_WAIT_BACKENDS;
+				pmState = PM_WAIT_BACKUP;
 			}
 
 			/*
-			 * Now wait for backends to exit.  If there are none,
+			 * Now wait for online backup mode to end and
+			 * backends to exit.  If that is already the case,
 			 * PostmasterStateMachine will take the next step.
 			 */
 			PostmasterStateMachine();
@@ -2011,6 +2017,13 @@ pmdie(SIGNAL_ARGS)
 			 * PostmasterStateMachine will take the next step.
 			 */
 			PostmasterStateMachine();
+
+			/*
+			 * Terminate backup mode to avoid recovery after a
+			 * clean fast shutdown.
+			 */
+			CancelBackup();
+
 			break;
 
 		case SIGQUIT:
@@ -2552,6 +2565,20 @@ LogChildExit(int lev, const char *procname, int pid, int exitstatus)
 static void
 PostmasterStateMachine(void)
 {
+	if (pmState == PM_WAIT_BACKUP)
+	{
+		/*
+		 * PM_WAIT_BACKUP state ends when online backup mode is no longer
+		 * active.  In this state canAcceptConnections() will still allow
+		 * client connections, which is necessary because a superuser
+		 * has to call pg_stop_backup() to end online backup mode.
+		 */
+		if (!BackupInProgress())
+		{
+			pmState = PM_WAIT_BACKENDS;
+		}
+	}
+
 	/*
 	 * If we are in a state-machine state that implies waiting for backends to
 	 * exit, see if they're all gone, and change state if so.
diff --git a/src/bin/pg_ctl/pg_ctl.c b/src/bin/pg_ctl/pg_ctl.c
index 89fc34d6860..55319c6262b 100644
--- a/src/bin/pg_ctl/pg_ctl.c
+++ b/src/bin/pg_ctl/pg_ctl.c
@@ -4,7 +4,7 @@
  *
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/bin/pg_ctl/pg_ctl.c,v 1.96 2008/02/29 23:31:20 adunstan Exp $
+ * $PostgreSQL: pgsql/src/bin/pg_ctl/pg_ctl.c,v 1.97 2008/04/23 13:44:59 mha Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -144,6 +144,7 @@ static char def_postopts_file[MAXPGPATH];
 static char postopts_file[MAXPGPATH];
 static char pid_file[MAXPGPATH];
 static char conf_file[MAXPGPATH];
+static char backup_file[MAXPGPATH];
 
 #if defined(HAVE_GETRLIMIT) && defined(RLIMIT_CORE)
 static void unlimit_core_size(void);
@@ -731,6 +732,7 @@ do_stop(void)
 {
 	int			cnt;
 	pgpid_t		pid;
+	struct stat	statbuf;
 
 	pid = get_pgpid();
 
@@ -763,6 +765,12 @@ do_stop(void)
 	}
 	else
 	{
+		if ((shutdown_mode == SMART_MODE) && (stat(backup_file, &statbuf) == 0))
+		{
+			print_msg(_("WARNING: online backup mode is active; must be ended\n"
+						"   with pg_stop_backup() for shutdown to complete\n\n"));
+		}
+
 		print_msg(_("waiting for server to shut down..."));
 
 		for (cnt = 0; cnt < wait_seconds; cnt++)
@@ -799,6 +807,7 @@ do_restart(void)
 {
 	int			cnt;
 	pgpid_t		pid;
+	struct stat	statbuf;
 
 	pid = get_pgpid();
 
@@ -833,6 +842,12 @@ do_restart(void)
 			exit(1);
 		}
 
+		if ((shutdown_mode == SMART_MODE) && (stat(backup_file, &statbuf) == 0))
+		{
+			print_msg(_("WARNING: online backup mode is active; must be ended\n"
+						"   with pg_stop_backup() for shutdown to complete\n\n"));
+		}
+
 		print_msg(_("waiting for server to shut down..."));
 
 		/* always wait for restart */
@@ -1883,6 +1898,7 @@ main(int argc, char **argv)
 		snprintf(postopts_file, MAXPGPATH, "%s/postmaster.opts", pg_data);
 		snprintf(pid_file, MAXPGPATH, "%s/postmaster.pid", pg_data);
 		snprintf(conf_file, MAXPGPATH, "%s/postgresql.conf", pg_data);
+		snprintf(backup_file, MAXPGPATH, "%s/backup_label", pg_data);
 	}
 
 	switch (ctl_command)
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index d06b34be437..3d1511e58a5 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.201 2008/02/20 22:46:24 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.202 2008/04/23 13:44:59 mha Exp $
  *
  * NOTES
  *	  some of the information in this file should be moved to other files.
@@ -330,4 +330,8 @@ extern void ValidatePgVersion(const char *path);
 extern void process_shared_preload_libraries(void);
 extern void process_local_preload_libraries(void);
 
+/* in access/transam/xlog.c */
+extern bool BackupInProgress(void);
+extern void CancelBackup(void);
+
 #endif   /* MISCADMIN_H */