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https://issues.apache.org/jira/browse/KAFKA-13405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17435853#comment-17435853
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Daniel O'Halloran commented on KAFKA-13405:
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Thanks for you your reply.
So we are using an FQDN which will resolve to our new broker IPs (see
KafkaConfig.txt). So there is no need to update our bootstrap.servers settings
after the upgrade.
However, this FQDN does not seem to be used by the restore-consumer to update
its cluster metadata during a rebalance. It keeps trying to use the old broker
IPs which it resolved on startup.
We would have expected that the bootstrap.server FQDN is re-resolved in case of
connection issues.
> Kafka Streams restore-consumer fails to refresh broker IPs after upgrading
> Kafka cluster
> ----------------------------------------------------------------------------------------
>
> Key: KAFKA-13405
> URL: https://issues.apache.org/jira/browse/KAFKA-13405
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 2.8.0, 2.7.1
> Reporter: Daniel O'Halloran
> Priority: Critical
> Attachments: KafkaConfig.txt, KafkaLogs.txt
>
>
> *+Description+*
> After upgrading our Kafka clusters from 2.7 to 2.8 the Streams
> restore-consumers never update their broker IPs.
> The applications continue to process events as normal, until there is a
> rebalance.
> Once a rebalance occurs the restore consumers attempts to connect to the old
> brokers IPs indefinitely and the streams tasks never go back into a RUNNING
> state.
> We were able to replicate this behaviour with kafka-streams client libraries
> 2.5.1, 2.7.1 and 2.8.0
>
> *+Steps to reproduce+*
> # Upgrade brokers from Kafka 2.7 to Kafka 2.8
> # Ensure old brokers are completely shut down
> # Trigger a rebalance of a streams application
>
> *+Expected result+*
> * Application rebalances as normal
>
> *+Actual Result+*
> * Application cannot restore its data
> * restore consumer tries to connect to old brokers indefinitely
>
> *+Observations+*
> * The cluster metadata was updated on all stream consumer threads during the
> broker upgrade (multiple times) as the new brokers were brought online
> (corresponding to leader election occurring on the subscribed partitions),
> however no cluster metadata was logged on the restore-consumer thread.
> * None of the original broker IPs are valid/accessible after the upgrade (as
> expected)
> * No partition rebalance occurs during the kafka upgrade process.
> * When the first re-balance was triggered after upgrade, the
> restore-consumer loops failing to connect on each of the 3 original IPs, but
> none of the new broker IPs.
>
> *+Workaround+*
> * Restart our applications after upgrading our Kafka cluster
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