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https://issues.apache.org/jira/browse/KAFKA-3083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15102791#comment-15102791
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Mayuresh Gharat commented on KAFKA-3083:
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[~junrao], [~fpj] that makes it more clear. I was just thinking if we can
modify the controller code to always check if it is the controller before it
makes such changes to zookeeper.
Again there is a race condition, wherein Broker A's session timesOut at time T.
Broker B becomes the controller at T+2. Broker A can still proceed with the
changes to ZK between T and T+2.
I had some questions on the zookeeper session expiry:
1) If suppose a broker establishes a connection with zookeeper and has a
ZookeeperSessionTimeout set to 10 min.The broker goes down/or is stuck and
comes back up and connects to zookeeper after 5 min, will it connect on the
same session?
2) The session Expiry is only invoked on SessionTimeout and nothing else. Am I
right?
> 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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