// Get the current queue length.
	qLen := n.q.Len()
	qLatency := n.calcQLatency(qLen)

	// Add the observations
	tnow := time.Now()
	n.qLength.AddObservation(float64(qLen), tnow)
	n.qLatency.AddObservation(qLatency.Seconds(), tnow)

	return n.serviceTime + qLatency
}

func (n *Node) calcQLatency(qlen int) time.Duration {
	if !n.qLatencyEnabled {
		return 0
	}