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https://issues.apache.org/jira/browse/KAFKA-19148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17949579#comment-17949579
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Azhar Ahmed commented on KAFKA-19148:
-------------------------------------
Ran the test for 3.9 Kraft cluster using the repro steps in the attached
Readme_Kraft.md
I was able to reproduce the issue and hence its a problem.
{code:java}
Processed 29000000 messages so far.
Processed 30000000 messages so far.
Processed 31000000 messages so far.
Inconsistency found: expected 31451085 but got 31457229
Inconsistency found: expected 31458253 but got 31456205
Inconsistency found: expected 31457229 but got 31455181
Inconsistency found: expected 31456205 but got 31454157
Inconsistency found: expected 31455181 but got 31453133
Inconsistency found: expected 31454157 but got 31458253
Processed 32000000 messages so far.
Processed 33000000 messages so far.
Processed 34000000 messages so far.
{code}
Next step: Deep dive into code and identify problematic piece of logic
> Potential Unclean Leader Election in KRaft Despite
> unclean.leader.election.enable=false
> ---------------------------------------------------------------------------------------
>
> Key: KAFKA-19148
> URL: https://issues.apache.org/jira/browse/KAFKA-19148
> Project: Kafka
> Issue Type: Bug
> Components: controller
> Affects Versions: 3.9.0, 4.0.0
> Reporter: Julian Bergner
> Assignee: Azhar Ahmed
> Priority: Critical
> Attachments: Readme_Kraft.md, Readme_Zookeeper.md,
> docker-compose_kraft.yml, docker-compose_zookeeper.yml
>
>
> *Issue Summary:*
> We're observing unclean leader election even though
> {{{}unclean.leader.election.enable=false{}}}.
> *Scenario:*
> During a partition reassignment, if we promote a non-ISR broker to leader and
> simultaneously remove the current leader from the ISR, Kafka still elects a
> new leader from outside the ISR. This behavior contradicts the expected
> behavior when unclean leader election is explicitly disabled.
> *Details:*
> * *Original ISR:* [1, 2]
> * *New ISR after reassignment:* [3, 2]
> *Kafka Versions Tested:*
> * Kafka 4.0.0 (KRaft mode)
> * Kafka 3.9.0 (Kraft mode)
> * Kafka 3.9.0 (Zookeeper mode)
> *Observation:*
> * The behaviour differs between the two modes.
> * In Kraft, unclean leader election occurred, which should not happen with
> the config set to {{{}false{}}}.
> * In Zookeeper no unclean leader election occurred.
> *Attachments:*
> Docker Compose files and reproduction steps for both:
> * Kafka 4.0.0 (KRaft)
> * Kafka 3.9.0 (Zookeeper)
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