KIP-423 — Add JoinReason to Consumer Join Group Protocol

Discussion ConsumerProtocol

Proposes adding a `joinReason` field to the `JoinGroup` request so that brokers can log the specific reason a consumer initiated a rebalance (new member, metadata change, leader rejoin, etc.), improving rebalance diagnostics as a complement to KIP-345's static membership work. Without structured join reasons, diagnosing why unnecessary rebalances occur requires correlating timestamps across broker and client logs with no explicit causal signal.

Protocol Impact

JoinGroup · LeaveGroup

Details