From: Fujii Masao <fujii@postgresql.org>
Date: Tue, 25 Apr 2017 16:07:13 +0000 (+0900)
Subject: Set the priorities of all quorum synchronous standbys to 1.
X-Git-Tag: REL_10_BETA1~174
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=346199dcab4cfb2c023373fb3d859583b59810d7;p=postgresql

Set the priorities of all quorum synchronous standbys to 1.

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
index 25c67aaac7..554f783209 100644
--- 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
index e11b4289d5..e56bbb9d86 100644
--- a/src/test/recovery/t/007_sync_rep.pl
+++ b/src/test/recovery/t/007_sync_rep.pl
@@ -186,7 +186,7 @@ standby4|0|async),
 # 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)');