Prevent BASE_BACKUP in the middle of another backup in the same session.

MasaoFujii · MasaoFujii · commit 286793b9889f · 2022-07-20T09:56:52.000+09:00
Multiple non-exclusive backups are able to be run conrrently in different sessions. But, in the same session, only one non-exclusive backup can be run at the same moment. If pg_backup_start (pg_start_backup in v14 or before) is called in the middle of another non-exclusive backup in the same session, an error is thrown. However, previously, in logical replication walsender mode, even if that walsender session had already called pg_backup_start and started a non-exclusive backup, it could execute BASE_BACKUP command and start another non-exclusive backup. Which caused subsequent pg_backup_stop to throw an error because BASE_BACKUP unexpectedly reset the session state marked by pg_backup_start. This commit prevents BASE_BACKUP command in the middle of another non-exclusive backup in the same session. Back-patch to all supported branches. Author: Fujii Masao Reviewed-by: Kyotaro Horiguchi, Masahiko Sawada, Michael Paquier, Robert Haas Discussion: https://postgr.es/m/3374718f-9fbf-a950-6d66-d973e027f44c@oss.nttdata.com
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
@@ -949,6 +949,12 @@ SendBaseBackup(BaseBackupCmd *cmd)
 {
 	basebackup_options opt;
 	bbsink	   *sink;
+	SessionBackupState status = get_backup_status();
+
+	if (status == SESSION_BACKUP_RUNNING)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("a backup is already in progress in this session")));
 
 	parse_basebackup_options(cmd->options, &opt);
 
