[jira] [Created] (KAFKA-8511) Looking into the Future: Heartbeat Communicated Protocol

["Guozhang Wang (JIRA)" <ji...@apache.org>]

Guozhang Wang created KAFKA-8511:
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             Summary: Looking into the Future: Heartbeat Communicated Protocol
                 Key: KAFKA-8511
                 URL: https://issues.apache.org/jira/browse/KAFKA-8511
             Project: Kafka
          Issue Type: Sub-task
            Reporter: Guozhang Wang


Note that KIP-429 relies on the fact that COOPERATIVE and EAGER members can work together within the same generation as long as the leader recognize both; this however may not be true moving forward if we add a third rebalance protocol. One idea to resolve this in the future is that, instead of letting the members to decide which protocol to use "locally" before sending the join-group request, we will use Heartbeat request / response to piggy-back the communication of the group's supported protocols and let members to rely on that "global" information to make decisions. More specifically:

* On Heartbeat Request, we will add additional field as a list of protocols that this member supports.
* On Heartbeat Response, we will add additional field as a single protocol indicating which to use if the error code suggests re-joining the group.

The broker, upon receiving the heartbeat request, if the indicated supported protocols does not contain the one it has decided to use for the up-coming rebalance, then reply with an fatal error.



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