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https://issues.apache.org/jira/browse/KAFKA-7968?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stanislav Kozlovski resolved KAFKA-7968.
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Resolution: Duplicate
This is a duplicate of https://issues.apache.org/jira/browse/KAFKA-7959.
Apologies for not realizing that was opened
> Delete leader epoch cache files with old message format versions
> ----------------------------------------------------------------
>
> Key: KAFKA-7968
> URL: https://issues.apache.org/jira/browse/KAFKA-7968
> Project: Kafka
> Issue Type: Bug
> Affects Versions: 2.0.1
> Reporter: Stanislav Kozlovski
> Assignee: Stanislav Kozlovski
> Priority: Major
>
> [KAFKA-7897 (Invalid use of epoch cache with old message format
> versions)|https://issues.apache.org/jira/browse/KAFKA-7897] fixed a critical
> bug where replica followers would inadequately use their leader epoch cache
> for truncating their logs upon becoming a follower. [The root of the
> issue|https://issues.apache.org/jira/browse/KAFKA-7897?focusedCommentId=16761049&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-16761049]
> was that a regression in KAFKA-7415 caused the leader epoch cache to be
> populated upon becoming a follower, even if the message format was older.
> KAFKA-7897 fixed that problem by not updating the leader epoch cache if the
> message format does not support it. It was merged all the way back to 1.1 but
> due to significant branch divergence, the patches for 2.0 and below were
> simplified. As said in the commit:
> Note this is a simplified fix than what was merged to trunk in #6232 since
> the branches have diverged significantly. Rather than removing the epoch
> cache file, we guard usage of the cache with the record version.
> This results in the same bug being hit at a different time. When the message
> format gets upgraded to support the leader epoch cache, brokers start to make
> use of it. Due to the previous problem, we still have the sparsely populated
> epoch cache file present. This results in the same large truncations we saw
> in KAFKA-7897.
> The key difference is that the patches for 2.1 and trunk *deleted* the
> non-empty leader epoch cache files if the log message format did not support
> it.
> We should update the earlier versions to do the same thing. That way, users
> that have upgraded to 2.0.1 but are still using old message formats/protocol
> will have their epochs cleaned up on the first roll that upgrades the
> `inter.broker.protocol.version`
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