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Posted to jira@kafka.apache.org by "David Jacot (Jira)" <ji...@apache.org> on 2023/11/21 13:47:00 UTC

[jira] [Commented] (KAFKA-15869) Document semantics of nullable nested API entities

    [ https://issues.apache.org/jira/browse/KAFKA-15869?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17788419#comment-17788419 ] 

David Jacot commented on KAFKA-15869:
-------------------------------------

[~antonagestam-aiven] No, it is not a mistake. We had a KIP for this: [https://cwiki.apache.org/confluence/display/KAFKA/KIP-893%3A+The+Kafka+protocol+should+support+nullable+structs.] However, I agree that we should update the protocol guide. We can use this Jira for this purpose.

> Document semantics of nullable nested API entities
> --------------------------------------------------
>
>                 Key: KAFKA-15869
>                 URL: https://issues.apache.org/jira/browse/KAFKA-15869
>             Project: Kafka
>          Issue Type: Wish
>            Reporter: Anton Agestam
>            Priority: Minor
>
> The initial version of ConsumerGroupHeartbeatResponse [introduced the first field across the protocol that is a nullable nested entity|https://github.com/dajac/kafka/blob/3acd87a3e82e1d2fd4c07218d362e7665b99c547/clients/src/main/resources/common/message/ConsumerGroupHeartbeatResponse.json#L48]. As the implementor of a third-party schema parser it is not clear how to handle this field, where such fields are allowed, and how null is represented for such fields.
> As far as I can tell, the [protocol guide|https://kafka.apache.org/protocol.html#The_Messages_ConsumerGroupHeartbeat] does not mention the nullability at all.
> The reason I ask where such fields are allowed is because if the answer to how null is represented here is just omitting writing any bytes, then I suspect the only unambiguous place for such field to appear would be as the last field of a top-level entity. Even then, how is it discriminated from tagged fields?
> Is it possible this field was made nullable by mistake?
>  



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