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https://issues.apache.org/jira/browse/FLINK-16686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17348602#comment-17348602
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Till Rohrmann commented on FLINK-16686:
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This could be an option to make the problem more visible to the user and
helping him not to shoot himself in the foot until we have fixed the problem
properly.
> [State TTL] Make user class loader available in native RocksDB compaction
> thread
> --------------------------------------------------------------------------------
>
> Key: FLINK-16686
> URL: https://issues.apache.org/jira/browse/FLINK-16686
> Project: Flink
> Issue Type: Bug
> Components: Runtime / State Backends
> Affects Versions: 1.8.0, 1.11.3, 1.13.0, 1.12.3
> Reporter: Andrey Zagrebin
> Priority: Minor
> Labels: auto-deprioritized-major
>
> The issue is initially reported
> [here|https://stackoverflow.com/questions/60745711/flink-kryo-serializer-because-chill-serializer-couldnt-be-found].
> The problem is that the java code of Flink compaction filter is called from
> RocksDB native C++ code. It is called in the context of the native compaction
> thread. RocksDB has utilities to create java Thread context for the Flink
> java callback. Presumably, the Java thread context class loader is not set at
> all and if it is queried then it produces NullPointerException.
> The provided report enabled a list state with TTL. The compaction filter has
> to deserialise elements to check expiration. The deserialiser relies on Kryo
> which queries the thread context class loader which is expected to be the
> user class loader of the task but turns out to be null.
> We should investigate how to pass the user class loader to the compaction
> thread of the list state with TTL.
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