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https://issues.apache.org/jira/browse/KAFKA-19850?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18035001#comment-18035001
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Luke Chen commented on KAFKA-19850:
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[~taijuwu], I know what you mean. But if a controller is joined as
`--initial-controllers` or `--standalone` controller, it will not be added via
addRaftVoterRequest/Response. So that means, when these controllers are
removed, it will still be auto-joined.
Do we have any way to get the initial controllers? Maybe parse the
"00000000000000000000-0000000000.checkpoint" and get the initial controller
lists? Is that a good solution?
> KRaft voter auto join will add a removed voter immediately
> ----------------------------------------------------------
>
> Key: KAFKA-19850
> URL: https://issues.apache.org/jira/browse/KAFKA-19850
> Project: Kafka
> Issue Type: Improvement
> Affects Versions: 4.2.0
> Reporter: Luke Chen
> Priority: Major
>
> In v4.2.0, we are able to auto join a controller with the configuration
> `controller.quorum.auto.join.enable=true` set
> ([KIP-853|https://cwiki.apache.org/confluence/display/KAFKA/KIP-853%3A+KRaft+Controller+Membership+Changes#KIP853:KRaftControllerMembershipChanges-Controllerautojoining](KAFKA-19078)).
> This is a good improvement for controller addition, but it has a UX issue,
> which is that when a controller is removed via removeVoterRequest, it will be
> added immediately due to `controller.quorum.auto.join.enable=true`. In the
> KIP, we also mention you have to stop the controller before removing the
> controller:
>
> {noformat}
> controller.quorum.auto.join.enable:
> Controls whether a KRaft controller should automatically join the cluster
> metadata partition for its cluster id. If the configuration is set to
> true the controller must be stopped before removing the controller with
> kafka-metadata-quorum remove-controller.{noformat}
>
> This is not a user friendly behavior in my opinion. And it will cause many
> confusion to users and thought there is something wrong in the controller
> removal. Furthermore, in the kubernetes environment which is controlled by
> the operator, it is not the cloud native way to shutdown a node, do some
> operation, then start it up.
>
> So, I propose we can improve it by "the removed controller will not be auto
> joined before this controller restarted". That is:
> 1. Once the controller is removed from voters set, it won't be auto joined
> even if `controller.quorum.auto.join.enable=true`
> 2. The controller can be manually join the voters in this state
> 3. The controller node will be auto join the voters set after node restarted.
>
> So basically, the semantics is not changed, it just add some unexpected
> remove/add loop. Thoughts?
>
>
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