Wake up launcher when enabling a subscription

petere · petere · commit a3f17b9c3155 · 2017-04-25T14:40:33.000-04:00
Otherwise one would have to wait up to DEFAULT_NAPTIME_PER_CYCLE until
the subscription worker is considered for starting.

There is a small race condition:  If one enables a subscription right
after disabling it, the launcher might not have registered the stopping
when receiving the wakeup signal for the re-enabling.  The start will
then not happen right away but after the full cycle time.

Author: Kyotaro HORIGUCHI &lt;horiguchi.kyotaro@lab.ntt.co.jp&gt;
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
@@ -644,6 +644,9 @@ AlterSubscription(AlterSubscriptionStmt *stmt)
 					BoolGetDatum(enabled);
 				replaces[Anum_pg_subscription_subenabled - 1] = true;
 
+				if (enabled)
+					ApplyLauncherWakeupAtCommit();
+
 				update_tuple = true;
 				break;
 			}

Original file line number	Diff line number	Diff line change
`@@ -644,6 +644,9 @@ AlterSubscription(AlterSubscriptionStmt *stmt)`
`644`	`644`	`BoolGetDatum(enabled);`
`645`	`645`	`replaces[Anum_pg_subscription_subenabled - 1] = true;`
`646`	`646`
	`647`	`+ if (enabled)`
	`648`	`+ ApplyLauncherWakeupAtCommit();`
	`649`	`+`
`647`	`650`	`update_tuple = true;`
`648`	`651`	`break;`
`649`	`652`	`}`