[jira] [Created] (KAFKA-10371) Partition reassignments can result in crashed ReplicaFetcherThreads.

["Steve Rodrigues (Jira)" <ji...@apache.org>]

Steve Rodrigues created KAFKA-10371:
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             Summary: Partition reassignments can result in crashed ReplicaFetcherThreads.
                 Key: KAFKA-10371
                 URL: https://issues.apache.org/jira/browse/KAFKA-10371
             Project: Kafka
          Issue Type: Bug
          Components: core
    Affects Versions: 2.7.0
            Reporter: Steve Rodrigues


A Kafka system doing partition reassignments got stuck with the reassignment partially done and the system with a non-zero number of URPs and increasing max lag.

Looking in the logs, we see: 
{noformat}
[ERROR] 2020-07-31 21:22:23,984 [ReplicaFetcherThread-0-3] kafka.server.ReplicaFetcherThread - [ReplicaFetcher replicaId=4, leaderId=3, fetcherId=0] Error due to
org.apache.kafka.common.errors.NotLeaderOrFollowerException: Error while fetching partition state for foo
[INFO] 2020-07-31 21:22:23,986 [ReplicaFetcherThread-0-3] kafka.server.ReplicaFetcherThread - [ReplicaFetcher replicaId=4, leaderId=3, fetcherId=0] Stopped
{noformat}

Investigating further and with some helpful changes to the exception (which was not generating a stack trace because it was a client-side exception), we see on a test run:

{noformat}
[2020-08-06 19:58:21,592] ERROR [ReplicaFetcher replicaId=2, leaderId=1, fetcherId=0] Error due to (kafka.server.ReplicaFetcherThread)
org.apache.kafka.common.errors.NotLeaderOrFollowerException: Error while fetching partition state for topic-test-topic-85
        at org.apache.kafka.common.protocol.Errors.exception(Errors.java:415)
        at kafka.server.ReplicaManager.getPartitionOrException(ReplicaManager.scala:645)
        at kafka.server.ReplicaManager.localLogOrException(ReplicaManager.scala:672)
        at kafka.server.ReplicaFetcherThread.logStartOffset(ReplicaFetcherThread.scala:133)
        at kafka.server.ReplicaFetcherThread.$anonfun$buildFetch$1(ReplicaFetcherThread.scala:316)
        at scala.collection.IterableOnceOps.foreach(IterableOnce.scala:553)
        at scala.collection.IterableOnceOps.foreach$(IterableOnce.scala:551)
        at scala.collection.AbstractIterable.foreach(Iterable.scala:920)
        at kafka.server.ReplicaFetcherThread.buildFetch(ReplicaFetcherThread.scala:309)
{noformat}

It appears that the fetcher is attempting to fetch for a partition that has been getting reassigned away. From further investigation, it seems that in KAFKA-10002 the StopReplica code was changed from:
1. Remove partition from fetcher
2. Remove partition from partition map
to the other way around, but now the fetcher may race and attempt to build a fetch for a partition that's no longer mapped.  In particular, since the logOrException code is being called from logStartOffset which isn't protected against NotLeaderOrFollowerException, just against KafkaStorageException, the exception isn't caught and throws all the way out, killing the replica fetcher thread.
We need to switch this back.






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