[
https://issues.apache.org/jira/browse/KAFKA-12679?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17630721#comment-17630721
]
A. Sophie Blee-Goldman commented on KAFKA-12679:
------------------------------------------------
Huh, I thought we had already fixed this a while ago but if you're still seeing
it on 2.8.1 then maybe I'm misremembering. If you're interested in submitting a
patch for this it would be welcome – I can backport it to older branches once
it's merged, but just a heads up it's unlikely for there to be another bugfix
release for 2.8. If you're willing/able to build from source then of course
this should be fine.
I'm pretty sure not much has changed in the initialization loop logic between
now and 2.8 so it should hopefully be a smooth cherrypick from trunk to 2.8,
but it might be worth poking around both branches when you are looking at a fix
to see if that fix will apply without conflicts to both.
Anyways if/when you have a patch ready, feel free to ping me directly on the PR
> Rebalancing a restoring or running task may cause directory livelocking with
> newly created task
> -----------------------------------------------------------------------------------------------
>
> Key: KAFKA-12679
> URL: https://issues.apache.org/jira/browse/KAFKA-12679
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 2.6.1
> Environment: Broker and client version 2.6.1
> Multi-node broker cluster
> Multi-node, auto scaling streams app instances
> Reporter: Peter Nahas
> Priority: Major
> Fix For: 3.4.0
>
> Attachments: Backoff-between-directory-lock-attempts.patch
>
>
> If a task that uses a state store is in the restoring state or in a running
> state and the task gets rebalanced to a separate thread on the same instance,
> the newly created task will attempt to lock the state store director while
> the first thread is continuing to use it. This is totally normal and expected
> behavior when the first thread is not yet aware of the rebalance. However,
> that newly created task is effectively running a while loop with no backoff
> waiting to lock the directory:
> # TaskManager tells the task to restore in `tryToCompleteRestoration`
> # The task attempts to lock the directory
> # The lock attempt fails and throws a
> `org.apache.kafka.streams.errors.LockException`
> # TaskManager catches the exception, stops further processing on the task
> and reports that not all tasks have restored
> # The StreamThread `runLoop` continues to run.
> I've seen some documentation indicate that there is supposed to be a backoff
> when this condition occurs, but there does not appear to be any in the code.
> The result is that if this goes on for long enough, the lock-loop may
> dominate CPU usage in the process and starve out the old stream thread task
> processing.
>
> When in this state, the DEBUG level logging for TaskManager will produce a
> steady stream of messages like the following:
> {noformat}
> 2021-03-30 20:59:51,098 DEBUG --- [StreamThread-10] o.a.k.s.p.i.TaskManager
> : stream-thread [StreamThread-10] Could not initialize 0_34 due
> to the following exception; will retry
> org.apache.kafka.streams.errors.LockException: stream-thread
> [StreamThread-10] standby-task [0_34] Failed to lock the state directory for
> task 0_34
> {noformat}
>
>
> I've attached a git formatted patch to resolve the issue. Simply detect the
> scenario and sleep for the backoff time in the appropriate StreamThread.
>
>
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
