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https://issues.apache.org/jira/browse/KAFKA-9739?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17064335#comment-17064335
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Artur commented on KAFKA-9739:
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Hey, Bill!
Thanks for looking into this issue. Both {{prepareForProcessing}} and
{{mapRecordToLookupEntry}} are key changing operations, so we cannot use
{{flatMapValues}} there. Sure, turning off optimizer for this topology is not a
problem at all. We would still be curious to know what makes this topology
special in a way that upsets existing optimization flow.
Regards,
Artur
> StreamsBuilder.build fails with StreamsException "Found a null
> keyChangingChild node for OptimizableRepartitionNode"
> --------------------------------------------------------------------------------------------------------------------
>
> Key: KAFKA-9739
> URL: https://issues.apache.org/jira/browse/KAFKA-9739
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 2.4.1
> Reporter: Artur
> Assignee: Bill Bejeck
> Priority: Major
> Attachments: streams-exception-log.txt,
> topology-definition-fragment.java, topology-description.txt
>
>
> We created a topology using Streams DSL (topology description is available in
> the attached topology-description.txt, no optimization).
> Topology works fine with {{topology.optimization=none}}, however it fails to
> build with StreamsException "Found a null keyChangingChild node for
> OptimizableRepartitionNode" if we set {{topology.optimization=all}}
> (exception stack trace is attached streams-exception-log.txt).
> We used [https://zz85.github.io/kafka-streams-viz/] to visualize topology and
> try to guess what might be upsetting optimizer, yet did not manage to figure
> it out ourselves.
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