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https://issues.apache.org/jira/browse/FLINK-25022?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Chesnay Schepler reassigned FLINK-25022:
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Assignee: Chesnay Schepler
> ClassLoader leak with ThreadLocals on the JM when submitting a job through
> the REST API
> ---------------------------------------------------------------------------------------
>
> Key: FLINK-25022
> URL: https://issues.apache.org/jira/browse/FLINK-25022
> Project: Flink
> Issue Type: Bug
> Components: Runtime / REST
> Affects Versions: 1.14.0, 1.12.5, 1.13.3
> Reporter: Nico Kruber
> Assignee: Chesnay Schepler
> Priority: Critical
> Fix For: 1.15.0, 1.14.1
>
>
> If a job is submitted using the REST API's {{/jars/:jarid/run}} endpoint,
> user code has to be executed on the JobManager and it is doing this in a
> couple of (pooled) dispatcher threads like
> {{{}Flink-DispatcherRestEndpoint-thread-*{}}}.
> If the user code is using thread locals (and not cleaning them up), they may
> remain in the thread with references to the {{ChildFirstClassloader}} of the
> job and thus leaking that.
> We saw this for the {{jsoniter}} scala library at the JM which [creates
> ThreadLocal
> instances|https://github.com/plokhotnyuk/jsoniter-scala/blob/95c7053cfaa558877911f3448382f10d53c4fcbf/jsoniter-scala-core/jvm/src/main/scala/com/github/plokhotnyuk/jsoniter_scala/core/package.scala]
> but doesn't remove them, but it can actually happen with any user code or
> (worse) library used in user code.
>
> There are a few *workarounds* a user can use, e.g. putting the library in
> Flink's lib/ folder or submitting via the Flink CLI, but these may actually
> not be possible to use, depending on the circumstances.
>
> A *proper fix* should happen in Flink by guarding against any of these things
> in the dispatcher threads. We could, for example, spawn a separate thread for
> executing the user's {{main()}} method and once the job is submitted exit
> that thread and destroy all thread locals along with it.
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