Set the priorities of all quorum synchronous standbys to 1.

MasaoFujii · MasaoFujii · commit 346199dcab4c · 2017-04-26T01:07:13.000+09:00
In quorum-based synchronous replication, all the standbys listed in synchronous_standby_names equally have chances to be chosen as synchronous standbys. So they should have the same priority. However, previously, quorum standbys whose names appear earlier in the list were given higher priority values though the difference of those priority values didn't affect the selection of synchronous standbys. Users could see those "meaningless" priority values in pg_stat_replication and this was confusing. This commit gives all the quorum synchronous standbys the same highest priority, i.e., 1, in order to remove such confusion. Author: Fujii Masao Reviewed-by: Masahiko Sawada, Kyotaro Horiguchi Discussion: http://postgr.es/m/CAHGQGwEKOw=SmPLxJzkBsH6wwDBgOnVz46QjHbtsiZ-d-2RGUg@mail.gmail.com
diff --git a/src/backend/replication/syncrep.c b/src/backend/replication/syncrep.c
@@ -951,7 +951,14 @@ SyncRepGetStandbyPriority(void)
 		standby_name += strlen(standby_name) + 1;
 	}
 
-	return (found ? priority : 0);
+	if (!found)
+		return 0;
+
+	/*
+	 * In quorum-based sync replication, all the standbys in the list
+	 * have the same priority, one.
+	 */
+	return (SyncRepConfig->syncrep_method == SYNC_REP_PRIORITY) ? priority : 1;
 }
 
 /*
diff --git a/src/test/recovery/t/007_sync_rep.pl b/src/test/recovery/t/007_sync_rep.pl
@@ -186,7 +186,7 @@ sub test_sync_state
 # for sync standbys in a quorum-based sync replication.
 test_sync_state(
 $node_master, qq(standby1|1|quorum
-standby2|2|quorum
+standby2|1|quorum
 standby4|0|async),
 '2 quorum and 1 async',
 'ANY 2(standby1, standby2)');

Original file line number	Diff line number	Diff line change
`@@ -951,7 +951,14 @@ SyncRepGetStandbyPriority(void)`
`951`	`951`	`standby_name += strlen(standby_name) + 1;`
`952`	`952`	`}`
`953`	`953`
`954`		`- return (found ? priority : 0);`
	`954`	`+ if (!found)`
	`955`	`+ return 0;`
	`956`	`+`
	`957`	`+ /*`
	`958`	`+ * In quorum-based sync replication, all the standbys in the list`
	`959`	`+ * have the same priority, one.`
	`960`	`+ */`
	`961`	`+ return (SyncRepConfig->syncrep_method == SYNC_REP_PRIORITY) ? priority : 1;`
`955`	`962`	`}`
`956`	`963`
`957`	`964`	`/*`