// 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
	}

	start := time.Now()
	c.total.Inc()
	c.active.Inc()

	wrappedDone := func() {
		// Calculate the latency for this request.
		latency := time.Since(start)

		// Add the latency observation.
		c.hist.AddObservation(latency.Seconds(), time.Now())

		c.active.Dec()

		// Invoke the caller's handler.
		onDone()
	}

	request(wrappedDone)

//  limitations under the License.

package timeseries

import (
	"sync"
	"time"
)

type Instance struct {
	data  Data
	times times
	mutex sync.Mutex
}

func (ts *Instance) AddObservation(val float64, t time.Time) {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()
	ts.data = append(ts.data, val)
	ts.times = append(ts.times, t)
}

func (ts *Instance) AddAll(o *Instance) {
	ts.mutex.Lock()