[jira] [Created] (KAFKA-21021) test_fencing_static_consumer is flaky for consumer protocol when duplicate static members do not start up at the same time.

["Sean Quah (Jira)" <ji...@apache.org>]

Sean Quah created KAFKA-21021:
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             Summary: test_fencing_static_consumer is flaky for consumer protocol when duplicate static members do not start up at the same time. 
                 Key: KAFKA-21021
                 URL: https://issues.apache.org/jira/browse/KAFKA-21021
             Project: Kafka
          Issue Type: Bug
          Components: system tests
            Reporter: Sean Quah


test_fencing_static_consumer creates a group with 3 static members (consumer) and tries to join 2 additional static members (conflict_consumer) using duplicate instance ids (num_conflict_consumers=2). Under the consumer protocol, the original 3 members are expected to remain active and keep their assignments, while the 2 duplicate-instance-id members are rejected with a fatal UnreleasedInstanceIdException and terminate.

The test uses VerifiableConsumer to start the duplicate-instance-id members, which considers them started when both nodes are simultaneously reporting a non-Dead state. But since these consumers are destined to die within about a second of starting, the "started" check only succeeds if both nodes happen to be alive at the same polling instant. If one node's startup lags behind the other's by more than ~1-second, the two nodes are never simultaneously non-Dead, and VerifiableConsumer.start() times out after 120 seconds with "Verifiable consumer didn't finish startup in 120 seconds," even though the fencing itself behaved correctly.



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