[jira] [Created] (KAFKA-8036) Log dir reassignment on followers fails with FileNotFoundException for the leader epoch cache on leader election

["Stanislav Kozlovski (JIRA)" <ji...@apache.org>]

Stanislav Kozlovski created KAFKA-8036:
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             Summary: Log dir reassignment on followers fails with FileNotFoundException for the leader epoch cache on leader election
                 Key: KAFKA-8036
                 URL: https://issues.apache.org/jira/browse/KAFKA-8036
             Project: Kafka
          Issue Type: Improvement
    Affects Versions: 2.0.1, 1.1.0, 1.0.2
            Reporter: Stanislav Kozlovski
            Assignee: Stanislav Kozlovski


When changing a partition's log directories for a follower broker, we move all the data related to that partition to the other log dir (as per [KIP-113|https://cwiki.apache.org/confluence/display/KAFKA/KIP-113:+Support+replicas+movement+between+log+directories]). On a successful move, we rename the original directory by adding a suffix consisting of an UUID and `-delete`. (e.g `test_log_dir` would be renamed to `test_log_dir-0.32e77c96939140f9a56a49b75ad8ec8d-delete`)

We copy every log file and [initialize a new leader epoch file cache|[https://github.com/apache/kafka/blob/0d56f1413557adabc736cae2dffcdc56a620403e/core/src/main/scala/kafka/log/Log.scala#L768].] The problem is that we do not update the associated `Replica` class' leader epoch cache - it still points to the old `LeaderEpochFileCache` instance.
This results in a FileNotFound exception when the broker is [elected as a leader for the partition|[https://github.com/apache/kafka/blob/255f4a6effdc71c273691859cd26c4138acad778/core/src/main/scala/kafka/cluster/Partition.scala#L312].] This has the unintended side effect of marking the log directory as offline, resulting in all partitions from that log directory becoming unavailable for the specific broker.



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