[GitHub] [kafka] guozhangwang commented on pull request #12041: MINOR: ignore unused configuration when ConsumerCoordinator is not constructed

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guozhangwang commented on PR #12041:
URL: https://github.com/apache/kafka/pull/12041#issuecomment-1117635812

   Thanks @C0urante for your thoughts. I'd like to clarify one thing that, today users can pass in both defined and unknown config values, where the latter may be used in some plugin modules (e.g. Kafka Streams's partition assignor). Since the `config.logUnused()` is called at the end of the the client constructor, at that time the latter category of configs may not be retrieved yet, and that does not mean that they will never be retrieved later after the constructor. So the logging message: "... were supplied but are not used yet." is reasonable, as "by that time" we do not know if they are never used or not, and we cannot just call `ignore` on all these configs in order to not log them.
   
   Now for the former case, generally we expect that by the time `config.logUnused()` is called, all defined configs should be retrieved. If the client does not retrieve them yet, AND users have specified values for those configs, it's debatable that we should let users know as a reminder that they can consider removing those overrides; whereas for those configs which are not overridden by users, we would not bother to let them know at all.
   
   If we want to do that, I'd suggest we do it universally: i.e. for all cases, including the previous `ignored` cases like `KEY_DESERIALIZER_CLASS_CONFIG`. Maybe you can send out a discussion email in the community to ask for a consensus?


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