long nextCheckTimeNs0() {
        BrokerHeartbeatState broker = unfenced.first();
        if (broker == null) {
            return Long.MAX_VALUE;
        } else {
            return broker.lastContactNs + sessionTimeoutNs;
        }
    }
Return the time in monotonic nanoseconds at which we should check if a broker
session needs to be expired.
metadata/src/main/java/org/apache/kafka/controller/BrokerHeartbeatManager.java