public OptionalLong registerBrokerRecordOffset(int brokerId) {
        Long registrationOffset = registerBrokerRecordOffsets.get(brokerId);
        if (registrationOffset != null) {
            return OptionalLong.of(registrationOffset);
        }
        return OptionalLong.empty();
    }
Process an incoming broker registration request.
metadata/src/main/java/org/apache/kafka/controller/ClusterControlManager.java