Jun Rao created KAFKA-1120:
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Summary: Controller could miss a broker state change
Key: KAFKA-1120
URL: https://issues.apache.org/jira/browse/KAFKA-1120
Project: Kafka
Issue Type: Bug
Components: core
Affects Versions: 0.8.1
Reporter: Jun Rao
When the controller is in the middle of processing a task (e.g., preferred
leader election, broker change), it holds a controller lock. During this time,
a broker could have de-registered and re-registered itself in ZK. After the
controller finishes processing the current task, it will start processing the
logic in the broker change listener. However, it will see no broker change and
therefore won't do anything to the restarted broker. This broker will be in a
weird state since the controller doesn't inform it to become the leader of any
partition. Yet, the cached metadata in other brokers could still list that
broker as the leader for some partitions. Client requests routed to that broker
will then get a TopicOrPartitionNotExistException. This broker will continue to
be in this bad state until it's restarted again.
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