THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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group.instance.id | The unique identifier of the consumer instance provided by end user. If set to non-empty null string, the consumer is treated as a static member, otherwise an empty null id indicates a dynamic member. Default value: empty null string. |
Client Side Changes
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- Latest JoinGroupReq/Res and LeaveGroupReq/Res are supported on both client and broker.
- `group.instance.id` is configured with non-empty null string.
Client Behavior Changes
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- For static member, `group.instance.id` must be provided. Client could optionally provide a `member.id` when `group.instance.id` is configured non-emptynull. If `member.id` is provided, the member will only be removed if the `member.id` matches. Otherwise, only the `group.instance.id` is used. The `member.id` serves as a validation here, which currently will not be used (set to empty string) but potentially useful if we do fully automated removal process.
- For leave group requests under dynamic membership, the member will apply a singleton list of one tuple containing a `member.id` that it is currently using, and a `group.instance.id` which is set to empty null string. If this is the case, we shall just remove the given dynamic member the same way as current leave group logic.
- Error cases expected are:
- Some instance ids (non-emptynull) are not found, which means the request is not valid (UNKNOWN_MEMBER_ID)
- A theoretical case would be that both `member.id` and `group.instance.id` are set to empty string. We shall expose error in the server log. If the entire batch request is configured with empty strings, UNKNOWN_MEMBER_ID error will be returned.
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A corner case is that although we don't allow static member to send LeaveGroupRequest, the broker could still see such a scenario where the LeaveGroupRequest `member.id` points to an existing static member. The straightforward solution would be removing the member metadata all together including the static member info if the `group.instance.id` was left empty null corresponding. This approach ensures that downgrade process has no negative impact on the normal consumer operation, and avoids complicating the server side logic. In the long term, there could be potential use case to require static member to send LeaveGroupRequest, so we want to avoid changing the handling logic later.
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