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https://issues.apache.org/jira/browse/FLINK-41100?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Martijn Visser updated FLINK-41100:
-----------------------------------
    Priority: Major  (was: Blocker)

> DynamicKafkaSource shares one split output between partitions whose split ids 
> collide
> -------------------------------------------------------------------------------------
>
>                 Key: FLINK-41100
>                 URL: https://issues.apache.org/jira/browse/FLINK-41100
>             Project: Flink
>          Issue Type: Bug
>          Components: Connectors / Kafka
>    Affects Versions: kafka-3.2.0, kafka-4.0.1, kafka-5.0.0
>            Reporter: Martijn Visser
>            Assignee: Martijn Visser
>            Priority: Major
>             Fix For: kafka-5.1.0
>
>
> {{DynamicKafkaSourceSplit#splitId}} is {{<cluster>-<topic>-<partition>}}, so 
> cluster {{a}} with topic {{b-c}} and cluster {{a-b}} with topic {{c}} both 
> get {{a-b-c-0}}. The sub-readers of {{DynamicKafkaSourceReader}} emit into 
> the same {{ReaderOutput}} under that id ({{KafkaPartitionSplitReaderWrapper}} 
> prefixes the cluster id), and {{createOutputForSplit}} returns the existing 
> output for an id it already knows. When one reader holds both partitions, 
> they share one split-local watermark generator, and when one of them 
> finishes, {{SourceReaderBase}} releases the output the other one still writes 
> to. From then on that partition no longer holds back the combined watermark, 
> so its records can be late. Watermark alignment pauses and resumes both 
> partitions together for the same reason.
> The split ids used towards Flink should be unique per physical partition. 
> FLINK-41088 fixes the same collision in the enumerator's recovery paths.



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