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https://issues.apache.org/jira/browse/KAFKA-999?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13730340#comment-13730340
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Neha Narkhede commented on KAFKA-999:
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>> However controller passing live brokers minus shutting down brokers as live
>> leaders in the LeaderAndIsrRequest sounds like a premature optimization and
>> a bug
Well, the field is not required only after this JIRA is fixed, but there is no
bug in the field. Like I explained above, live leaders cannot include the
broker being shut down, so the controller passes accurate information to the
broker. The bug is in the way the broker uses that field.
Deleting the field in the future is a good idea. However, it is a change in
wire protocol, so I suggest we file that JIRA and handle that part on trunk.
> Controlled shutdown never succeeds until the broker is killed
> -------------------------------------------------------------
>
> Key: KAFKA-999
> URL: https://issues.apache.org/jira/browse/KAFKA-999
> Project: Kafka
> Issue Type: Bug
> Components: controller
> Affects Versions: 0.8
> Reporter: Neha Narkhede
> Assignee: Neha Narkhede
> Priority: Critical
>
> A race condition in the way leader and isr request is handled by the broker
> and controlled shutdown can lead to a situation where controlled shutdown can
> never succeed and the only way to bounce the broker is to kill it.
> The root cause is that broker uses a smart to avoid fetching from a leader
> that is not alive according to the controller. This leads to the broker
> aborting a become follower request. And in cases where replication factor is
> 2, the leader can never be transferred to a follower since it keeps rejecting
> the become follower request and stays out of the ISR. This causes controlled
> shutdown to fail forever
> One sequence of events that led to this bug is as follows -
> - Broker 2 is leader and controller
> - Broker 2 is bounced (uncontrolled shutdown)
> - Controller fails over
> - Controlled shutdown is invoked on broker 1
> - Controller starts leader election for partitions that broker 2 led
> - Controller sends become follower request with leader as broker 1 to broker
> 2. At the same time, it does not include broker 1 in alive broker list sent
> as part of leader and isr request
> - Broker 2 rejects leaderAndIsr request since leader is not in the list of
> alive brokers
> - Broker 1 fails to transfer leadership to broker 2 since broker 2 is not in
> ISR
> - Controlled shutdown can never succeed on broker 1
> Since controlled shutdown is a config option, if there are bugs in controlled
> shutdown, there is no option but to kill the broker
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