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public static Schema[] schemaVersions() {
    return new Schema[] {JOIN_GROUP_RESPONSE_V0, JOIN_GROUP_RESPONSE_V1, JOIN_GROUP_RESPONSE_V2, JOIN_GROUP_RESPONSE_V3, JOIN_GROUP_RESPONSE_V4};
}

Also notice that we have a conflicting internal config called LEAVE_GROUP_ON_CLOSE_CONFIG which decides whether a consumer should send a leave group request upon going offline. This would make the effectiveness of this KIP less because after leaving the consumer group, the broker will identify the same member as a new member which would still trigger a lot of rebalances. We will set this internal config default to false if enabling with member name.

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For the effectiveness of the KIP, consumer with member.name set will not send leave group request when they go offline. It is because the current rebalance protocol will trigger rebalance with this intermittent in-and-out which is not ideal. 

Server behavior changes

On server side, broker will keep handling join group request <= v3 as before. If the protocol version is upgraded to v4 and the member name is set, the broker will use the member name specified in the join group request and respond with a unique "member id".  Broker will maintain an in-memory mapping of {member.name → member.id} to track member uniqueness.

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