MINOR: trivial cleanups

[dongjinleekr]

1. Remove unused imports from CommandLineUtils, KafkaConfig.
2. Add ignore case in KafkaController#process, GroupCoordinator#doSyncGroup, and GroupCoordinator#handleHeartbeat.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[ijuma]

Thanks for the PR. Ignoring the exhaustiveness warnings can hide bugs, if we don't expect it to happen, we should throw an exception.

[abbccdda]

Don't need this because the Dead case is being handled already in the upstream.

[dongjinleekr]

You mean, if (group.is(Dead)) { in the line 350, right? Then, how to suppress not-exhaustive match warning? Do you have any idea?

[hachikuji]

We could raise an exception since we expect to have handled this state. I think it is better to be exhaustive with matches. In fact, I'd prefer to handle case Dead explicitly rather than a blind case _. That way the compiler will generate a warning if we add a new state and don't update this. In other words, the warning will have value.

[abbccdda]

Same here

[hachikuji]

Thanks @dongjinleekr . Left a minor suggestion. Otherwise, looks good.

[hachikuji]

Can we provide a more useful message? These impossible states have a funny way of becoming possible over time 😉 . Maybe something like this?

throw new IllegalStateException(s"Reached unexpected condition for Dead group $groupId")

We can probably remove the comment if the exception message is already clear.

[dongjinleekr]

Here is the fix. cc/ @abbccdda @hachikuji

[hachikuji]

LGTM. Thanks @dongjinleekr !

[ijuma]

Shouldn't we throw an exception here too?

[dongjinleekr]

Well, I have been still thinking about it; If we need an Exception, I will apply it in next cleanup. @abbccdda Could you tell me your opinion?

[ijuma]

Previously we would throw an exception (MatchError) and now we ignore it. That seems worse, right?

[hachikuji]

Yes, you are right. I went ahead and merged because it was being addressed in #6686.

[ijuma]

Makes sense, we can just do it in #6686 then.