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In the join request v3, it is user's responsibility to assign unique member id for each consumers. This could be in service discovery hostname, unique IP address, etc. The downside is that if user configured the member id wrongly, there could be multiple consumers with the same member id, which invalidates the consumption balance and triggers unpredictable buggy behaviors. We could think of a way to detect this. 

If the MEMBER_ID config is not set, Another approach would be that the consumer client be using client id + random generated number to get a new unique member id, the same way as broker would do.

Compatibility, Deprecation, and Migration Plan

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