Fix connection leak in DROP SUBSCRIPTION command, take 2.

MasaoFujii · MasaoFujii · commit 77d21970ae19 · 2017-03-08T23:43:38.000+09:00
Commit 898a792 fixed the connection leak issue, but it was an unreliable way of bugfix. This bugfix was assuming that walrcv_command() subroutine cannot throw an error, but it's untenable assumption. For example, if it will be changed so that an error is thrown, connection leak issue will happen again. This patch ensures that the connection is closed even when walrcv_command() subroutine throws an error. Patch by me, reviewed by Petr Jelinek and Michael Paquier Discussion: https://www.postgresql.org/message-id/2058.1487704345@sss.pgh.pa.us
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
@@ -565,19 +565,25 @@ DropSubscription(DropSubscriptionStmt *stmt, bool isTopLevel)
 						"drop the replication slot \"%s\"", slotname),
 				 errdetail("The error was: %s", err)));
 
-	if (!walrcv_command(wrconn, cmd.data, &err))
+	PG_TRY();
+	{
+		if (!walrcv_command(wrconn, cmd.data, &err))
+			ereport(ERROR,
+					(errmsg("could not drop the replication slot \"%s\" on publisher",
+							slotname),
+					 errdetail("The error was: %s", err)));
+		else
+			ereport(NOTICE,
+					(errmsg("dropped replication slot \"%s\" on publisher",
+							slotname)));
+	}
+	PG_CATCH();
 	{
 		/* Close the connection in case of failure */
 		walrcv_disconnect(wrconn);
-		ereport(ERROR,
-				(errmsg("could not drop the replication slot \"%s\" on publisher",
-						slotname),
-				 errdetail("The error was: %s", err)));
+		PG_RE_THROW();
 	}
-	else
-		ereport(NOTICE,
-				(errmsg("dropped replication slot \"%s\" on publisher",
-						slotname)));
+	PG_END_TRY();
 
 	walrcv_disconnect(wrconn);
 
