[jira] [Created] (KAFKA-14201) Consumer should not send group instance ID if committing with empty member ID

["Jason Gustafson (Jira)" <ji...@apache.org>]

Jason Gustafson created KAFKA-14201:
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             Summary: Consumer should not send group instance ID if committing with empty member ID
                 Key: KAFKA-14201
                 URL: https://issues.apache.org/jira/browse/KAFKA-14201
             Project: Kafka
          Issue Type: Bug
            Reporter: Jason Gustafson


The consumer group instance ID is used to support a notion of "static" consumer groups. The idea is to be able to identify the same group instance across restarts so that a rebalance is not needed. However, if the user sets `group.instance.id` in the consumer configuration, but uses "simple" assignment with `assign()`, then the instance ID nevertheless is sent in the OffsetCommit request to the coordinator. This may result in a surprising UNKNOWN_MEMBER_ID error. The consumer should probably be smart enough to only send the instance ID when committing as part of a consumer group.



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