Lianet Magrans created KAFKA-16816:
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Summary: Remove unneeded FencedInstanceId support on commit path
for new consumer
Key: KAFKA-16816
URL: https://issues.apache.org/jira/browse/KAFKA-16816
Project: Kafka
Issue Type: Task
Components: clients, consumer
Reporter: Lianet Magrans
The new consumer contains logic related to handling FencedInstanceId exception
received as a response to an OffsetCommit request (on the
[consumer|https://github.com/apache/kafka/blob/028e7a06dcdca7d4dbeae83f2fce0a4120cc2753/clients/src/main/java/org/apache/kafka/clients/consumer/internals/AsyncKafkaConsumer.java#L776]
and [commit
manager|https://github.com/apache/kafka/blob/028e7a06dcdca7d4dbeae83f2fce0a4120cc2753/clients/src/main/java/org/apache/kafka/clients/consumer/internals/CommitRequestManager.java#L715]),
but with the new group protocol, we will never get that error on a commit
response. We should remove the code that expects the FencedInstanceId on the
commit response, and also clean up the other related usages that we added to
propagate the FencedInstanceId exception on the poll, commitSync and
commitAsync API. Note that throwing that exception is part of the contract of
the poll, commitSync and commitAsync APIs of the KafkaConsumer, but it changes
with the new protocol. We should update the java doc for the new
AsyncKafkaConsumer to reflect the change.
With the new protocol If a consumer tries to commit offsets, there could be 2
cases:
# empty group -> commit succeeds, fencing an instance id would never happen
because group is empty
# non-empty group -> commit fails with UnknownMemberId, indicating that the
member is not known to the group. The consumer needs to join the non-empty
group in order to commit offsets to it. To complete the story, the moment the
consumer attempts to join, it will receive an UnreleasedInstanceId error on the
HB response, indicating it using a groupInstanceId that is already in use.
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