[jira] [Commented] (BEAM-13924) Coder information lost in Kafka Read

["Kenneth Knowles (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BEAM-13924?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17494152#comment-17494152 ] 

Kenneth Knowles commented on BEAM-13924:
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Checking {{git log ^v2.29.0 v2.36.0 -- sdks/java/io/kafka}} there are quite a few pull requests that seem like they could introduce such problems, such as #15028 #16339 #15951. Maybe [~chamikara] will be able to quickly identify the root cause from the history.

> Coder information lost in Kafka Read
> ------------------------------------
>
>                 Key: BEAM-13924
>                 URL: https://issues.apache.org/jira/browse/BEAM-13924
>             Project: Beam
>          Issue Type: Bug
>          Components: io-java-kafka
>    Affects Versions: 2.36.0
>            Reporter: Jonas Grabber
>            Priority: P2
>              Labels: bug, kafka
>
> When upgrading from 2.29.0 to 2.36.0 our Kafka Read transform broke.
> While debugging, I saw that information of the key and value coders is lost after [this statement in KafkaIO|https://github.com/apache/beam/blob/v2.36.0/sdks/java/io/kafka/src/main/java/org/apache/beam/sdk/io/kafka/KafkaIO.java#L1459]:
> {code:java}
> return output.apply(readTransform).setCoder(KafkaRecordCoder.of(keyCoder, valueCoder));
> {code}
> The issue seems to be that {{output.apply}} already checks for the presence of key and value coders and ends up trying to infer them with the help of [LocalDeserializerProvider|https://github.com/apache/beam/blob/v2.36.0/sdks/java/io/kafka/src/main/java/org/apache/beam/sdk/io/kafka/LocalDeserializerProvider.java], so the process never arrives at {{{}setCoder{}}}.
> In our case this inference fails since we implement the {{Deserializer}} interface in a super class of the instance passed as the deserializer (I assume it would also fail afterwards since we don't register our coders with the registry).
> This was not yet broken on 2.29.0, so all versions after that could be affected.



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