PatrickRen opened a new pull request, #21806:
URL: https://github.com/apache/flink/pull/21806
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## What is the purpose of the change
> The analysis below was initially made by @SmirAlex in #21365
This pull-request *tries to fix* unstable test `LookupJoinITCase` (error was
not succeeded to be reproduced locally). An error contains the message 'Trying
to access closed classloader'. However, test configured in the way that it
loads cache only one time, and we wait until the end of this load in
`LookupFullCache#open`. So `LookupFullCache#close` shouldn't somehow affect on
cache load thread, if we assume that `close` is called only after `open`.
During debugging it was found out that in `GenericRowDataKeySelector#open`,
which executes inside separate reload thread, call of
`Thread.currentThread().getContextClassLoader()` returns `SubmoduleClassLoader`
rather than `FlinkUserCodeClassLoader`, which is being returned from the same
method inside main thread. *Probably*, this ClassLoader should not be there,
and this is the core of the problem. Also it closely relates to the problem
about classloader leak, described in option
`CoreOptions#CHECK_LEAKED_CLASSLOADER`, to which error points out.
This change prevents from compiling a class in another separate thread, but
rather do it just one time in main thread in `LookupFullCache#open` using
provided userCodeClassLoader. Subsequent calls of
`GeneratedProjection#newInstance` will end up with creating an instance from
cached `Class<Projection>` without compilation or another interaction with
context classloader. Note, that provided classloader is not stored anywhere, so
classloader leak problem can't occur anymore.
## Brief change log
- Compile Projection Class in main thread in `LookupFullCache#open` to
avoid classloader leak
- Set context classloader to UserCodeClassLoader in
`InputSplitCacheLoadTask`
## Verifying this change
- This change is already covered by existing tests.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (no)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (no)
- The serializers: (no)
- The runtime per-record code paths (performance sensitive): (no)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (no)
- The S3 file system connector: (no)
## Documentation
- Does this pull request introduce a new feature? (no)
- If yes, how is the feature documented? (not applicable)
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