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https://issues.apache.org/jira/browse/FLINK-30474?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17650811#comment-17650811
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Matthias Pohl commented on FLINK-30474:
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The leader check is actually handled in the
{{MultipleComponentLeaderElectionDriver}} implementations (see
[ZooKeeperMultipleComponentLeaderElectionDriver:203|https://github.com/apache/flink/blob/8ddfd590ebba7fc727e79db41b82d3d40a02b56a/flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/ZooKeeperMultipleComponentLeaderElectionDriver.java#L203]
and
[ZooKeeperMultipleComponentLeaderElectionDriver:223|https://github.com/apache/flink/blob/8ddfd590ebba7fc727e79db41b82d3d40a02b56a/flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/ZooKeeperMultipleComponentLeaderElectionDriver.java#L223]
for ZooKeeper and
[KubernetesMultipleComponentLeaderElectionDriver:238|https://github.com/apache/flink/blob/0290715a57b8d243586ab747b0cd2416c8081012/flink-kubernetes/src/main/java/org/apache/flink/kubernetes/highavailability/KubernetesMultipleComponentLeaderElectionDriver.java#L238]
for Kubernetes. But this only triggers the sending of the change information
which is then executed in a separate thread in
[DefaultMultipleComponentLeaderElectionService#sendLeaderInformationChange|https://github.com/apache/flink/blob/715c3fdef515c4b7ac70c4abd52910c08d6ca662/flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/DefaultMultipleComponentLeaderElectionService.java#L247].
Therefore, the leader role could have changed in the meantime.
> DefaultMultipleComponentLeaderElectionService triggers HA backend change even
> if it's not the leader
> ----------------------------------------------------------------------------------------------------
>
> Key: FLINK-30474
> URL: https://issues.apache.org/jira/browse/FLINK-30474
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Coordination
> Affects Versions: 1.16.0, 1.17.0, 1.15.3
> Reporter: Matthias Pohl
> Assignee: Matthias Pohl
> Priority: Critical
>
> {{DefaultMultipleComponentLeaderElectionService}} calls
> {{LeaderElectionEventHandler#onLeaderInformationChange}} in any case even
> though the contracts of that method states that it should be only called by
> the leader to update the HA backend information (see
> [JavaDoc|https://github.com/apache/flink/blob/5a2f220e31c50306a60aae8281f0ab4073fb85e1/flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/LeaderElectionEventHandler.java#L46-L50]).
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