[jira] [Commented] (KAFKA-13029) FindCoordinators batching can break consumers during rolling upgrade

["Mickael Maison (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-13029?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17373734#comment-17373734 ] 

Mickael Maison commented on KAFKA-13029:
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Right, I missed that!

For the Consumer/Producer, I guess we could reset the batch flag in AbstractCoordinator each time the coordinator changes. 

For AdminClient, we create a new CoordinatorStrategy for each call but I think this could still happen if the coordinator changes during a call while we upgrade brokers. It's a bit more tricky because the strategy doesn't know explicitly if the coordinator just changed.

> FindCoordinators batching can break consumers during rolling upgrade
> --------------------------------------------------------------------
>
>                 Key: KAFKA-13029
>                 URL: https://issues.apache.org/jira/browse/KAFKA-13029
>             Project: Kafka
>          Issue Type: Bug
>          Components: consumer
>            Reporter: Rajini Sivaram
>            Assignee: Rajini Sivaram
>            Priority: Blocker
>             Fix For: 3.0.0
>
>
> The changes made under KIP-699 assume that it is always safe to use unbatched mode since we move from batched to unbatched and cache the value forever in clients if a broker doesn't support batching. During rolling upgrade, if a request is sent to an older broker, we move from batched to unbatched mode. The consumer (admin client as well I think) disables batching and future requests to upgraded brokers will fail because we attempt to use unbatched requests with a newer version of the request.



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