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https://issues.apache.org/jira/browse/KAFKA-6671?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ray Chiang updated KAFKA-6671:
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Component/s: consumer
> Consumer group coordinator releases group before new coordinator is ready.
> --------------------------------------------------------------------------
>
> Key: KAFKA-6671
> URL: https://issues.apache.org/jira/browse/KAFKA-6671
> Project: Kafka
> Issue Type: Bug
> Components: consumer
> Affects Versions: 0.10.2.1
> Reporter: Rob Gevers
> Priority: Major
>
> We regularly have an issue with our Kafka deploys which causes consumers to
> be unable to consume for an extended period of time (up to an hour) after the
> deploy finishes. The issue appears to be a side-effect of the way consumer
> group coordination is managed between nodes. A sample timeline of a deploy
> looks like the following:
> We initiate a clean shutdown of a node (which we will call kafka-2). We see
> these traces:
> {noformat}
> [2018-02-20 09:13:46,935] INFO [GroupCoordinator 1]: Loading group metadata
> for ConsumerGroup with generation 3041
> (kafka.coordinator.GroupCoordinator){noformat}
> {noformat}
> [2018-02-20 09:13:47,788] INFO [GroupCoordinator 2]: Unloading group
> metadata for ConsumerGroup with generation 3041{noformat}
> At this point kafka-2 is shutdown and restarted successfully. Consumers
> continue to function fine. Once kafka-2 is back online we see this trace from
> kafka-1
> {noformat}
> [2018-02-20 09:49:30,486] INFO [GroupCoordinator 1]: Unloading group
> metadata for ConsumerGroup with generation 3041{noformat}
> At this point the consumers go into a loop of "Discovered coordinator
> Kafka-2"Marking the coordinator Kafka-2 dead". This preempts the heartbeat
> timer and we even see the heartbeat rate metrics drop to 0. This continues
> until kafka-2 has finished processing offset data and finally traces
> {noformat}
> [2018-02-20 10:52:28,956] INFO [GroupCoordinator 2]: Loading group metadata
> for ConsumerGroup with generation 3041
> (kafka.coordinator.GroupCoordinator){noformat}
> What seems like a bug to me is that kafka-1 is unloading the consumer group
> long before kafka-2 is ready to load it. This seems to leave the group in an
> unusable state, with offset commits failing because they are trying to commit
> to kafka-2, but kafka-2 keeps responding that it isn't the group coordinator.
> There is no coordinator for an hour.
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