XComp commented on code in PR #22422:
URL: https://github.com/apache/flink/pull/22422#discussion_r1173943821
##########
flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/LeaderElectionEventHandler.java:
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@@ -39,12 +40,29 @@ public interface LeaderElectionEventHandler {
*/
void onGrantLeadership(UUID newLeaderSessionId);
+ /**
+ * Called by specific {@link LeaderElectionDriver} when the leadership is
granted.
+ *
+ * <p>This method will trigger the grant event processing in a separate
thread.
+ *
+ * @param newLeaderSessionId the valid leader session id
+ */
+ CompletableFuture<Void> onGrantLeadershipAsync(UUID newLeaderSessionId);
Review Comment:
How would we determine that we're running in the main thread? We would need
to get a reference to the owner of `DefaultLeaderElectionService`, wouldn't we?
That way we would be able to check whether the call is run in the main thread
of the owner. But this would closer coupling of the owner and the
`DefaultLeaderElectionService`. Or do you have something else in mind which I'm
missing? :thinking:
My understanding is that we have the following requirements:
* `onGrantLeadership`, `onRevokeLeadership` and `onLeaderInformationChanged`
should be called in a single thread to ensure sequential execution.
* the methods shouldn't be called in the main thread of the
`LeaderElectionService`'s owner. The k8s and ZK implementation do this
implicitly through their event thread handling. The
`DefaultMultipleComponentLeaderElectionService` doesn't do that (anymore). But
that's an implementation detail of the service. That's why I thought that it's
also the `DefaultMultipleComponentLeaderElectionService`'s responsibility to
call the event processing functions asynchronously.
WDYT?
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