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https://issues.apache.org/jira/browse/KAFKA-15372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17755647#comment-17755647
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Greg Harris commented on KAFKA-15372:
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[~durban] I should clarify, I believe the behavior you described is the
expected (but undesirable) behavior for versions before 3.5.0 and earlier, and
for 3.5.0+ with the configuration set to the default `false`.
When the internal REST API is enabled, the worker which is starting (that is
not the leader) should forward configurations to the leader via the internal
REST API. If you're not seeing the REST forwarding being attempted, or the
forwarding failing, that would explain why configuration updates are being
dropped.
If the above does not apply, then I'm interested to hear more details of your
reproduction case. Thanks!
> MM2 rolling restart can drop configuration changes silently
> -----------------------------------------------------------
>
> Key: KAFKA-15372
> URL: https://issues.apache.org/jira/browse/KAFKA-15372
> Project: Kafka
> Issue Type: Improvement
> Components: mirrormaker
> Reporter: Daniel Urban
> Priority: Major
>
> When MM2 is restarted, it tries to update the Connector configuration in all
> flows. This is a one-time trial, and fails if the Connect worker is not the
> leader of the group.
> In a distributed setup and with a rolling restart, it is possible that for a
> specific flow, the Connect worker of the just restarted MM2 instance is not
> the leader, meaning that Connector configurations can get dropped.
> For example, assuming 2 MM2 instances, and one flow A->B:
> # MM2 instance 1 is restarted, the worker inside MM2 instance 2 becomes the
> leader of A->B Connect group.
> # MM2 instance 1 tries to update the Connector configurations, but fails
> (instance 2 has the leader, not instance 1)
> # MM2 instance 2 is restarted, leadership moves to worker in MM2 instance 1
> # MM2 instance 2 tries to update the Connector configurations, but fails
> At this point, the configuration changes before the restart are never
> applied. Many times, this can also happen silently, without any indication.
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