[jira] [Comment Edited] (KAFKA-5036) Followups from KIP-101

["Ben Stopford (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-5036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15962827#comment-15962827 ] 

Ben Stopford edited comment on KAFKA-5036 at 4/10/17 6:42 PM:
--------------------------------------------------------------

Points 2, 5 are addressed in PR: https://github.com/apache/kafka/pull/2831
Point 3 is addressed in PR: https://github.com/apache/kafka/pull/2821 (now merged)
Point 4 has been addressed (fixing tests). Changed the log line to an assert (which [~junrao] and I discussed previously)


was (Author: benstopford):
Points 2, 5 are addressed in PR: https://github.com/apache/kafka/pull/2831
Point 3 is addressed in PR: https://github.com/apache/kafka/pull/2821 (now merged)
Point 4 is an issue only in the test. The LogTest sets up a Log with an empty epoch cache. Not addressed at this time.  

> Followups from KIP-101
> ----------------------
>
>                 Key: KAFKA-5036
>                 URL: https://issues.apache.org/jira/browse/KAFKA-5036
>             Project: Kafka
>          Issue Type: Improvement
>    Affects Versions: 0.11.0.0
>            Reporter: Jun Rao
>            Assignee: Jun Rao
>             Fix For: 0.11.0.0
>
>
> 1. It would be safer to hold onto the leader lock in Partition while serving an OffsetForLeaderEpoch request.
> 2. Currently, we update the leader epoch in epochCache after log append in the follower but before log append in the leader. It would be more consistent to always do this after log append. This also avoids issues related to failure in log append.
> 3. OffsetsForLeaderEpochRequest/OffsetsForLeaderEpochResponse:
> The code that does grouping can probably be replaced by calling CollectionUtils.groupDataByTopic(). Done: https://github.com/apache/kafka/commit/359a68510801a22630a7af275c9935fb2d4c8dbf
> 4. The following line in LeaderEpochFileCache is hit several times when LogTest is executed:
> {code}
>        if (cachedLatestEpoch == None) error("Attempt to assign log end offset to epoch before epoch has been set. This should never happen.")
> {code}
> This should be an assert (with the tests fixed up)
> 5. The constructor of LeaderEpochFileCache has the following:
> {code}
> lock synchronized { ListBuffer(checkpoint.read(): _*) }
> {code}
> But everywhere else uses a read or write lock. We should use consistent locking.



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