Jason Gustafson created KAFKA-5586:
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Summary: Handle client disconnects during JoinGroup
Key: KAFKA-5586
URL: https://issues.apache.org/jira/browse/KAFKA-5586
Project: Kafka
Issue Type: Bug
Reporter: Jason Gustafson
If a consumer disconnects with a JoinGroup in-flight, we do not remove it from
the group until after the Join phase completes. If the client immediately
re-sends the JoinGroup request and it already had a memberId, then the callback
will be replaced and there is no harm done. For the other cases:
1. If the client disconnected due to a failure and does not re-send the
JoinGroup, the consumer will still be included in the new group generation
after the rebalance completes, but will immediately timeout and trigger a new
rebalance.
2. If the consumer was not a member of the group and re-sends JoinGroup, then a
new memberId will be created for that consumer and the old one will not be
removed. When the rebalance completes, the old memberId will timeout and a
rebalance will be triggered.
To address these issues, we should add some additional logic to handle client
disconnections during the join phase. For newly generated memberIds, we should
simply remove them. For existing members, we should probably leave them in the
group and reset the heartbeat expiration task.
Note that we currently have no facility to expose disconnects from the network
layer to the other layers, so we need to find a good approach for this.
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