[jira] [Commented] (KAFKA-6681) Two instances of kafka consumer reading the same partition within a consumer group

["Ted Yu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-6681?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16421556#comment-16421556 ] 

Ted Yu commented on KAFKA-6681:
-------------------------------

I assume you use StickyAssignor.

Can you switch to RoundRobinAssignor and see if the problem persists ?

Thanks

> Two instances of kafka consumer reading the same partition within a consumer group
> ----------------------------------------------------------------------------------
>
>                 Key: KAFKA-6681
>                 URL: https://issues.apache.org/jira/browse/KAFKA-6681
>             Project: Kafka
>          Issue Type: Bug
>          Components: clients, consumer
>    Affects Versions: 0.10.2.1
>            Reporter: Narayan Periwal
>            Priority: Critical
>         Attachments: server-1.log, server-2.log
>
>
> We have seen this issue with the Kafka consumer, the new library that got introduced in 0.9
> With this new client, the group management is done by kafka coordinator, which is one of the kafka broker.
> We are using Kafka broker 0.10.2.1 and consumer client version is also 0.10.2.1 
> The issue that we have faced is that, after rebalancing, some of the partitions gets consumed by 2 instances within a consumer group, leading to duplication of the entire partition data. Both the instances continue to read until the next rebalancing, or the restart of those clients. 
> It looks like that a particular consumer goes on fetching the data from a partition, but the broker is not able to identify this "stale" consumer instance. 
> We have hit this twice in production. Please look at it the earliest. 



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