Minbo Bae created BEAM-14189:
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Summary: NullPointerException or IllegalStateException at
IsmReaderImpl in Dataflow
Key: BEAM-14189
URL: https://issues.apache.org/jira/browse/BEAM-14189
Project: Beam
Issue Type: Bug
Components: runner-dataflow
Reporter: Minbo Bae
h6. Problem
Dataflow Java batch jobs with large side input intermittently throws
{{NullPointerException}} or {{{}IllegalStateException{}}}.
*
[NullPointerException|https://gist.githubusercontent.com/baeminbo/459e283eadbc7752c9f23616b52d958a/raw/f0480b8eaff590fb3f3ae2ab98ddce7dd3b4a237/npe.png]
happens at
[IsmReaderImpl.overKeyComponents|https://github.com/apache/beam/blob/v2.37.0/runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/IsmReaderImpl.java#L217]:
*
[IllegalStateException|https://gist.githubusercontent.com/baeminbo/459e283eadbc7752c9f23616b52d958a/raw/f0480b8eaff590fb3f3ae2ab98ddce7dd3b4a237/IllegalStateException.png]
happens at [IsmReaderImpl. initializeForKeyedRead
|https://github.com/apache/beam/blob/v2.37.0/runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/IsmReaderImpl.java#L500].
(all error logs in the Dataflow job is
[here|https://gist.githubusercontent.com/baeminbo/459e283eadbc7752c9f23616b52d958a/raw/f0480b8eaff590fb3f3ae2ab98ddce7dd3b4a237/downloaded-logs-20220327-171955.json].)
h6. Hypothesis
The {{initializeForKeyedRead}} is not synchronized. Multiple threads can enter
the method so that initialize the index for the same shard and update
{{indexPerShard}} without synchronization. And, the {{overKeyComponents}} also
accesses {{indexPerShard}} without synchronization. As {{indexPerShard}} is
just a {{HashMap}} which is not thread-safe, it can cause
{{NullPointerException}} and {{IllegalStateException}} above.
h6. Suggestion
I think it can fix this issue if we change the type of {{indexPerShard}} to a
thread-safe map (e.g. {{ConcurrentHashMap}}).
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