[jira] [Commented] (KAFKA-19334) MetadataShell bypasses file lock unexpectedly due to lock file deletion

["TengYao Chi (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-19334?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17956815#comment-17956815 ] 

TengYao Chi commented on KAFKA-19334:
-------------------------------------

Cherry pick to 3.9 and 4.0

> MetadataShell bypasses file lock unexpectedly due to lock file deletion
> -----------------------------------------------------------------------
>
>                 Key: KAFKA-19334
>                 URL: https://issues.apache.org/jira/browse/KAFKA-19334
>             Project: Kafka
>          Issue Type: Bug
>    Affects Versions: 4.0.0
>            Reporter: Haruki Okada
>            Assignee: Haruki Okada
>            Priority: Major
>             Fix For: 3.9.2, 4.0.1, 4.1.0
>
>
> MetadataShell acquires log dir lock to prevent unexpected results by concurrent reads/writes fixed by [https://github.com/apache/kafka/pull/14899].
>  
> This lock works as expected when we execute MetadataShell against running log for the first time:
>  
> {code:java}
> % ./bin/kafka-metadata-shell.sh --snapshot data/bootstrap.checkpoint
> Unexpected error: Unable to lock /path/to/data. Please ensure that no broker or controller process is using this directory before proceeding.{code}
> However, if we execute MetadataShell with same command again with controller still running, it succeeds unexpectedly.
>  
>  
> {code:java}
> % ./bin/kafka-metadata-shell.sh --snapshot data/bootstrap.checkpoint
> Loading...
> Starting...
> [ Kafka Metadata Shell ]
> >> {code}
> And I found that .lock file vanishes after MetadataShell exit.
>  
> This is because MetadataShell calls FileLock#destroy when it fails acquiring lock, which deletes the lock file.
> [https://github.com/apache/kafka/blob/4.0.0/shell/src/main/java/org/apache/kafka/shell/MetadataShell.java#L131]
>  



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