Minor Description
KRaft brokers maintain their liveness in the cluster by sending BROKER_HEARTBEAT requests to the active controller; the active controller fences a broker if it doesn't receive a heartbeat request from that broker within the period defined by `broker.session.timeout.ms`. The broker should use a request timeout for its BROKER_HEARTBEAT requests that is not larger than the session timeout being used by the controller; doing so creates the possibility that upon controller failover the broker might not cancel an existing heartbeat request in time and then subsequently heartbeat to the new controller to maintain an uninterrupted session in the cluster. In other words, a failure of the active controller could result in under-replicated (or under-min ISR) partitions simply due to a delay in brokers heartbeating to the new controller.
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