Expose waitforarchive option through pg_stop_backup()

Internally, we have supported the option to either wait for all of the
WAL associated with a backup to be archived, or to return immediately.
This option is useful to users of pg_stop_backup() as well, when they
are reading the stop backup record position and checking that the WAL
they need has been archived independently.

This patch adds an additional, optional, argument to pg_stop_backup()
which allows the user to indicate if they wish to wait for the WAL to be
archived or not.  The default matches current behavior, which is to
wait.

Author: David Steele, with some minor changes, doc updates by me.
Reviewed by: Takayuki Tsunakawa, Fujii Masao
Discussion: https://postgr.es/m/758e3fd1-45b4-5e28-75cd-e9e7f93a4c02@pgmasters.net

5 files changed, 21 insertions, 6 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index ff4cf3a810b..3924738a336 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -10944,7 +10944,8 @@ do_pg_stop_backup(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p)
 	 *
 	 * We wait forever, since archive_command is supposed to work and we
 	 * assume the admin wanted his backup to work completely. If you don't
-	 * wish to wait, you can set statement_timeout.  Also, some notices are
+	 * wish to wait, then either waitforarchive should be passed in as false,
+	 * or you can set statement_timeout.  Also, some notices are
 	 * issued to clue in anyone who might be doing this interactively.
 	 */
 	if (waitforarchive && XLogArchivingActive())
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 96aa15e9cc3..5073aaca84f 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -175,6 +175,13 @@ pg_stop_backup(PG_FUNCTION_ARGS)
  * the backup label and tablespace map files as text fields in as part of the
  * resultset.
  *
+ * The first parameter (variable 'exclusive') allows the user to tell us if
+ * this is an exclusive or a non-exclusive backup.
+ *
+ * The second paramter (variable 'waitforarchive'), which is optional,
+ * allows the user to choose if they want to wait for the WAL to be archived
+ * or if we should just return as soon as the WAL record is written.
+ *
  * Permission checking for this function is managed through the normal
  * GRANT system.
  */
@@ -190,6 +197,7 @@ pg_stop_backup_v2(PG_FUNCTION_ARGS)
 	bool		nulls[3];
 
 	bool		exclusive = PG_GETARG_BOOL(0);
+	bool		waitforarchive = PG_GETARG_BOOL(1);
 	XLogRecPtr	stoppoint;
 
 	/* check to see if caller supports us returning a tuplestore */
@@ -232,7 +240,7 @@ pg_stop_backup_v2(PG_FUNCTION_ARGS)
 		 * Stop the exclusive backup, and since we're in an exclusive backup
 		 * return NULL for both backup_label and tablespace_map.
 		 */
-		stoppoint = do_pg_stop_backup(NULL, true, NULL);
+		stoppoint = do_pg_stop_backup(NULL, waitforarchive, NULL);
 		exclusive_backup_running = false;
 
 		nulls[1] = true;
@@ -250,7 +258,7 @@ pg_stop_backup_v2(PG_FUNCTION_ARGS)
 		 * Stop the non-exclusive backup. Return a copy of the backup label
 		 * and tablespace map so they can be written to disk by the caller.
 		 */
-		stoppoint = do_pg_stop_backup(label_file->data, true, NULL);
+		stoppoint = do_pg_stop_backup(label_file->data, waitforarchive, NULL);
 		nonexclusive_backup_running = false;
 		cancel_before_shmem_exit(nonexclusive_base_backup_cleanup, (Datum) 0);
 
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index b6552da4b03..c2b0bedc1d6 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -988,6 +988,12 @@ CREATE OR REPLACE FUNCTION
   RETURNS pg_lsn STRICT VOLATILE LANGUAGE internal AS 'pg_start_backup'
   PARALLEL RESTRICTED;
 
+CREATE OR REPLACE FUNCTION pg_stop_backup (
+        exclusive boolean, wait_for_archive boolean DEFAULT true,
+        OUT lsn pg_lsn, OUT labelfile text, OUT spcmapfile text)
+  RETURNS SETOF record STRICT VOLATILE LANGUAGE internal as 'pg_stop_backup_v2'
+  PARALLEL RESTRICTED;
+
 -- legacy definition for compatibility with 9.3
 CREATE OR REPLACE FUNCTION
   json_populate_record(base anyelement, from_json json, use_json_as_text boolean DEFAULT false)
@@ -1088,7 +1094,7 @@ AS 'jsonb_insert';
 -- available to superuser / cluster owner, if they choose.
 REVOKE EXECUTE ON FUNCTION pg_start_backup(text, boolean, boolean) FROM public;
 REVOKE EXECUTE ON FUNCTION pg_stop_backup() FROM public;
-REVOKE EXECUTE ON FUNCTION pg_stop_backup(boolean) FROM public;
+REVOKE EXECUTE ON FUNCTION pg_stop_backup(boolean, boolean) FROM public;
 REVOKE EXECUTE ON FUNCTION pg_create_restore_point(text) FROM public;
 REVOKE EXECUTE ON FUNCTION pg_switch_wal() FROM public;
 REVOKE EXECUTE ON FUNCTION pg_wal_replay_pause() FROM public;
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index b4f1b9a6c2a..315f155b645 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201703161
+#define CATALOG_VERSION_NO	201703221
 
 #endif
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 836d6ff0b20..22635655f56 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -3172,7 +3172,7 @@ DATA(insert OID = 2172 ( pg_start_backup		PGNSP PGUID 12 1 0 0 0 f f f f t f v r
 DESCR("prepare for taking an online backup");
 DATA(insert OID = 2173 ( pg_stop_backup			PGNSP PGUID 12 1 0 0 0 f f f f t f v r 0 0 3220 "" _null_ _null_ _null_ _null_ _null_ pg_stop_backup _null_ _null_ _null_ ));
 DESCR("finish taking an online backup");
-DATA(insert OID = 2739 ( pg_stop_backup			PGNSP PGUID 12 1 1 0 0 f f f f t t v r 1 0 2249 "16" "{16,3220,25,25}" "{i,o,o,o}" "{exclusive,lsn,labelfile,spcmapfile}" _null_ _null_ pg_stop_backup_v2 _null_ _null_ _null_ ));
+DATA(insert OID = 2739 ( pg_stop_backup			PGNSP PGUID 12 1 1 0 0 f f f f t t v r 2 0 2249 "16 16" "{16,16,3220,25,25}" "{i,i,o,o,o}" "{exclusive,wait_for_archive,lsn,labelfile,spcmapfile}" _null_ _null_ pg_stop_backup_v2 _null_ _null_ _null_ ));
 DESCR("finish taking an online backup");
 DATA(insert OID = 3813 ( pg_is_in_backup		PGNSP PGUID 12 1 0 0 0 f f f f t f v s 0 0 16 "" _null_ _null_ _null_ _null_ _null_ pg_is_in_backup _null_ _null_ _null_ ));
 DESCR("true if server is in online backup");