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https://issues.apache.org/jira/browse/KAFKA-3083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15097330#comment-15097330
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Flavio Junqueira commented on KAFKA-3083:
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One clarification, if broker A shrinks the partition ISR in ZK before step 2
but notifies C after step 2 as in the description, does C eventually learn the
ISR stored in ZK? If it doesn't, then the observation about connection loss
might not be sufficient to fix it or even matter at all in this case.
> a soft failure in controller may leader a topic partition in an inconsistent
> state
> ----------------------------------------------------------------------------------
>
> Key: KAFKA-3083
> URL: https://issues.apache.org/jira/browse/KAFKA-3083
> Project: Kafka
> Issue Type: Bug
> Components: core
> Affects Versions: 0.9.0.0
> Reporter: Jun Rao
> Assignee: Mayuresh Gharat
>
> The following sequence can happen.
> 1. Broker A is the controller and is in the middle of processing a broker
> change event. As part of this process, let's say it's about to shrink the isr
> of a partition.
> 2. Then broker A's session expires and broker B takes over as the new
> controller. Broker B sends the initial leaderAndIsr request to all brokers.
> 3. Broker A continues by shrinking the isr of the partition in ZK and sends
> the new leaderAndIsr request to the broker (say C) that leads the partition.
> Broker C will reject this leaderAndIsr since the request comes from a
> controller with an older epoch. Now we could be in a situation that Broker C
> thinks the isr has all replicas, but the isr stored in ZK is different.
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