A. Sophie Blee-Goldman created KAFKA-12984:
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Summary: Cooperative sticky assignor can get stuck with invalid
SubscriptionState input metadata
Key: KAFKA-12984
URL: https://issues.apache.org/jira/browse/KAFKA-12984
Project: Kafka
Issue Type: Bug
Components: consumer
Reporter: A. Sophie Blee-Goldman
Fix For: 3.0.0, 2.8.1
Some users have reported seeing their consumer group become stuck in the
CompletingRebalance phase when using the cooperative-sticky assignor. Based on
the request metadata we were able to deduce that multiple consumers were
reporting the same partition(s) in their "ownedPartitions" field of the
consumer protocol. Since this is an invalid state, the input causes the
cooperative-sticky assignor to detect that something is wrong and throw an
IllegalStateException. If the consumer application is set up to simply retry,
this will cause the group to appear to hang in the rebalance state.
The "ownedPartitions" field is encoded based on the ConsumerCoordinator's
SubscriptionState, which was assumed to always be up to date. However there may
be cases where the consumer has dropped out of the group but fails to clear the
SubscriptionState, allowing it to report some partitions as owned that have
since been reassigned to another member.
We should (a) fix the sticky assignment algorithm to resolve cases of improper
input conditions by invalidating the "ownedPartitions" in cases of double
ownership, and (b) shore up the ConsumerCoordinator logic to better handle
rejoining the group and keeping its internal state consistent. See KAFKA-12983
for more details on (b)
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