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https://issues.apache.org/jira/browse/FLINK-15024?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yingjie Cao updated FLINK-15024:
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Labels: (was: stale-major)
> System classloader memory leak after loading too many codegen classes.
> ----------------------------------------------------------------------
>
> Key: FLINK-15024
> URL: https://issues.apache.org/jira/browse/FLINK-15024
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Runtime
> Reporter: Yingjie Cao
> Priority: Major
>
> We are using Flink session cluster as a service for ad-hoc queries. After
> running some queries, we found that the memory usage of TaskManager grows and
> cannot be garbage collected. Eventually, we found that it was the object
> (class name and lock object) in parallelLockMap of AppClassloader and
> ExtClassloader cannot be recycled. And we found the classes were generated
> ones and should be never loaded by system classloader.
> The codegen classes are loaded by org.codehaus.janino.ByteArrayClassLoader
> which is a parent first classloader and will rely on its parent classloader,
> e.g. Flink user classloader to load the class first, flink user classloader
> will also try to load the class with its parent classloader, and finally it
> will reach AppClassloader and ExtClassloader. Both the AppClassloader and
> ExtClassloader are SecureClassLoader and will add class name and a lock
> object to the parallelLockMap when loading a new class.
> I think we should never let the system classloader try to load the generated
> classes which is doomed to fail. We need to prune the process of loading
> codegen classes and avoid those classes reaching the system classloader. Two
> ways can achieve that:
> # We give a special prefix to codegen class name and filter class with those
> prefix in Flink user classloader.
> # We implement a new child first classloader which filters the codegen class
> and never loads the codegen class with Flink user classloader and set this
> class loader as the parent classloader of
> org.codehaus.janino.ByteArrayClassLoader instead of the Flink user
> classloader.
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