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Date: Tue, 5 Jan 2016 22:01:39 +0000 (UTC)
From: "Jason Gustafson (JIRA)" <jira@apache.org>
To: dev@kafka.apache.org
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Subject: [jira] [Commented] (KAFKA-3059) ConsumerGroupCommand should allow
 resetting offsets for consumer groups
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    [ https://issues.apache.org/jira/browse/KAFKA-3059?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15083922#comment-15083922 ] 

Jason Gustafson commented on KAFKA-3059:
----------------------------------------

One problem is defining the behavior of these operations when the consumer group is still active. The simple option would be to forbid them. Users would have to shutdown all consumers in the group, which actually seems pretty reasonable. But if there are legitimate use cases which call for overriding offsets while a group is still active, then it will take some tricky coordination to get all group members to reload offsets.

As far as implementation, writing to the offsets topic directly does not seem viable since there would be no way to verify whether the group is active or not. Even if we wanted to support offset updates while the group is active, it would still require some coordination with the group coordinator. That means we'll either need to override the commit API to support deletion (e.g. by using -1 as the offset for each partition as someone suggested on the user list), or introduce a DeleteOffsets API. Either way, this will probably need a KIP. 


> ConsumerGroupCommand should allow resetting offsets for consumer groups
> -----------------------------------------------------------------------
>
>                 Key: KAFKA-3059
>                 URL: https://issues.apache.org/jira/browse/KAFKA-3059
>             Project: Kafka
>          Issue Type: Bug
>            Reporter: Gwen Shapira
>            Assignee: Jason Gustafson
>
> As discussed here:
> http://mail-archives.apache.org/mod_mbox/kafka-users/201601.mbox/%3CCA%2BndhHpf3ib%3Ddsh9zvtfVjRiUjSz%2B%3D8umXm4myW%2BpBsbTYATAQ%40mail.gmail.com%3E
> * Given a consumer group, remove all stored offsets
> * Given a group and a topic, remove offset for group  and topic
> * Given a group, topic, partition and offset - set the offset for the specified partition and group with the given value


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