[jira] [Commented] (FLINK-8409) Race condition in KafkaConsumerThread leads to potential NPE

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-8409?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16354356#comment-16354356 ] 

ASF GitHub Bot commented on FLINK-8409:
---------------------------------------

Github user asfgit closed the pull request at:

    https://github.com/apache/flink/pull/5329


> Race condition in KafkaConsumerThread leads to potential NPE
> ------------------------------------------------------------
>
>                 Key: FLINK-8409
>                 URL: https://issues.apache.org/jira/browse/FLINK-8409
>             Project: Flink
>          Issue Type: Bug
>          Components: Kafka Connector
>    Affects Versions: 1.4.0, 1.3.2, 1.5.0
>            Reporter: Tzu-Li (Gordon) Tai
>            Assignee: Tzu-Li (Gordon) Tai
>            Priority: Blocker
>             Fix For: 1.3.3, 1.5.0, 1.4.1
>
>
> The following lines in the {{KafkaConsumerThread::setOffsetsToCommit(...)}} suggests a race condition with the asynchronous callback from committing offsets to Kafka:
> {code}
> // record the work to be committed by the main consumer thread and make sure the consumer notices that
> if (nextOffsetsToCommit.getAndSet(offsetsToCommit) != null) {
>     log.warn("Committing offsets to Kafka takes longer than the checkpoint interval. " +
>         "Skipping commit of previous offsets because newer complete checkpoint offsets are available. " +
>         "This does not compromise Flink's checkpoint integrity.");
> }
> this.offsetCommitCallback = commitCallback;
> {code}
> In the main consumer thread's main loop, {{nextOffsetsToCommit}} will be checked if there are any offsets to commit. If so, an asynchronous offset commit operation will be performed. The NPE happens in the case when the commit completes, but {{this.offsetCommitCallback = commitCallback;}} is not yet reached.
> A possible fix is to make setting the next offsets to commit along with the callback instance a single atomic operation.



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