[jira] [Resolved] (SPARK-53948) Fix deadlock in Observation

["Gengliang Wang (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-53948?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Gengliang Wang resolved SPARK-53948.
------------------------------------
    Fix Version/s: 3.5.8
       Resolution: Fixed

Issue resolved by pull request 52657
[https://github.com/apache/spark/pull/52657]

> Fix deadlock in Observation
> ---------------------------
>
>                 Key: SPARK-53948
>                 URL: https://issues.apache.org/jira/browse/SPARK-53948
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 3.5.7
>            Reporter: L. C. Hsieh
>            Assignee: L. C. Hsieh
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 3.5.8
>
>
> Observation class has been evolved a few times during Spark 3.5 to Spark 4.0.0. Previously it uses locking mechanism (synchronized) between get and onFinish methods to coordinate metrics update and retrieval.
> But it has a potential deadlocking bug. If get is called before ObservationListener is triggered to call onFinish, get will forever be waiting for metrics because it locks the observation object by synchronized so later onFinish call is locked out from updating the metrics.
> This locking mechanism was replaced by a promise by SPARK-49423 which is a large refactoring on the observation feature. But in the PR, I don’t see the deadlock bug was mentioned, and there is no bug fix PR proposed to earlier versions. So I think that the bug was not known and the fix is unintentional in Spark 4.0.0. The bug is still in Spark 3.5 branch.



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