Use Registerer to Register All Metrics

* Made Metric a Gauge so that it can be registered.

cmd/prometheus/main.go

@@ -184,7 +184,6 @@ func Main() int {
 	if instrumentedStorage, ok := localStorage.(prometheus.Collector); ok {
 		prometheus.MustRegister(instrumentedStorage)
 	}
-	prometheus.MustRegister(notifier)
 	prometheus.MustRegister(configSuccess)
 	prometheus.MustRegister(configSuccessTime)
 

notifier/notifier.go

@@ -83,11 +83,11 @@ type alertMetrics struct {
 	errors        *prometheus.CounterVec
 	sent          *prometheus.CounterVec
 	dropped       prometheus.Counter
-	queueLength   prometheus.Gauge
-	queueCapacity prometheus.Metric
+	queueLength   prometheus.GaugeFunc
+	queueCapacity prometheus.Gauge
 }
 
-func newAlertMetrics(r prometheus.Registerer, o *Options) *alertMetrics {
+func newAlertMetrics(r prometheus.Registerer, queueCap int, queueLen func() float64) *alertMetrics {
 	m := &alertMetrics{
 		latency: prometheus.NewSummaryVec(prometheus.SummaryOpts{
 			Namespace: namespace,
@@ -119,29 +119,30 @@ func newAlertMetrics(r prometheus.Registerer, o *Options) *alertMetrics {
 			Name:      "dropped_total",
 			Help:      "Total number of alerts dropped due to errors when sending to Alertmanager.",
 		}),
-		queueLength: prometheus.NewGauge(prometheus.GaugeOpts{
+		queueLength: prometheus.NewGaugeFunc(prometheus.GaugeOpts{
 			Namespace: namespace,
 			Subsystem: subsystem,
 			Name:      "queue_length",
 			Help:      "The number of alert notifications in the queue.",
+		}, queueLen),
+		queueCapacity: prometheus.NewGauge(prometheus.GaugeOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "queue_capacity",
+			Help:      "The capacity of the alert notifications queue.",
 		}),
-		queueCapacity: prometheus.MustNewConstMetric(
-			prometheus.NewDesc(
-				prometheus.BuildFQName(namespace, subsystem, "queue_capacity"),
-				"The capacity of the alert notifications queue.",
-				nil, nil,
-			),
-			prometheus.GaugeValue,
-			float64(o.QueueCapacity),
-		),
 	}
 
+	m.queueCapacity.Set(float64(queueCap))
+
 	if r != nil {
 		r.MustRegister(
 			m.latency,
 			m.errors,
 			m.sent,
 			m.dropped,
+			m.queueLength,
+			m.queueCapacity,
 		)
 	}
 
@@ -156,14 +157,17 @@ func New(o *Options) *Notifier {
 		o.Do = ctxhttp.Do
 	}
 
-	return &Notifier{
-		queue:   make(model.Alerts, 0, o.QueueCapacity),
-		ctx:     ctx,
-		cancel:  cancel,
-		more:    make(chan struct{}, 1),
-		opts:    o,
-		metrics: newAlertMetrics(o.Registerer, o),
+	n := &Notifier{
+		queue:  make(model.Alerts, 0, o.QueueCapacity),
+		ctx:    ctx,
+		cancel: cancel,
+		more:   make(chan struct{}, 1),
+		opts:   o,
 	}
+
+	queueLenFunc := func() float64 { return float64(n.queueLen()) }
+	n.metrics = newAlertMetrics(o.Registerer, o.QueueCapacity, queueLenFunc)
+	return n
 }
 
 // ApplyConfig updates the status state as the new config requires.
@@ -406,20 +410,6 @@ func (n *Notifier) Stop() {
 	n.cancel()
 }
 
-// Describe implements prometheus.Collector.
-func (n *Notifier) Describe(ch chan<- *prometheus.Desc) {
-	ch <- n.metrics.queueCapacity.Desc()
-	ch <- n.metrics.queueLength.Desc()
-}
-
-// Collect implements prometheus.Collector.
-func (n *Notifier) Collect(ch chan<- prometheus.Metric) {
-	n.metrics.queueLength.Set(float64(n.queueLen()))
-
-	ch <- n.metrics.queueLength
-	ch <- n.metrics.queueCapacity
-}
-
 // alertmanager holds Alertmanager endpoint information.
 type alertmanager interface {
 	url() string

notifier/notifier_test.go

@@ -25,7 +25,6 @@ import (
 
 	"golang.org/x/net/context"
 
-	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/config"
 )
@@ -64,7 +63,6 @@ func TestPostPath(t *testing.T) {
 
 func TestHandlerNextBatch(t *testing.T) {
 	h := New(&Options{})
-	defer unregisterMetrics()
 
 	for i := range make([]struct{}, 2*maxBatchSize+1) {
 		h.queue = append(h.queue, &model.Alert{
@@ -120,14 +118,6 @@ func alertsEqual(a, b model.Alerts) bool {
 	return true
 }
 
-func unregisterMetrics() {
-	m := newAlertMetrics(nil, &Options{})
-	prometheus.DefaultRegisterer.Unregister(m.latency)
-	prometheus.DefaultRegisterer.Unregister(m.errors)
-	prometheus.DefaultRegisterer.Unregister(m.sent)
-	prometheus.DefaultRegisterer.Unregister(m.dropped)
-}
-
 func TestHandlerSendAll(t *testing.T) {
 	var (
 		expected         model.Alerts
@@ -160,7 +150,6 @@ func TestHandlerSendAll(t *testing.T) {
 	defer server2.Close()
 
 	h := New(&Options{})
-	defer unregisterMetrics()
 	h.alertmanagers = append(h.alertmanagers, &alertmanagerSet{
 		ams: []alertmanager{
 			alertmanagerMock{
@@ -228,7 +217,6 @@ func TestCustomDo(t *testing.T) {
 			}, nil
 		},
 	})
-	defer unregisterMetrics()
 
 	h.sendOne(context.Background(), nil, testURL, []byte(testBody))
 
@@ -251,7 +239,6 @@ func TestExternalLabels(t *testing.T) {
 			},
 		},
 	})
-	defer unregisterMetrics()
 
 	// This alert should get the external label attached.
 	h.Send(&model.Alert{
@@ -306,7 +293,6 @@ func TestHandlerRelabel(t *testing.T) {
 			},
 		},
 	})
-	defer unregisterMetrics()
 
 	// This alert should be dropped due to the configuration
 	h.Send(&model.Alert{
@@ -361,7 +347,6 @@ func TestHandlerQueueing(t *testing.T) {
 	h := New(&Options{
 		QueueCapacity: 3 * maxBatchSize,
 	})
-	defer unregisterMetrics()
 	h.alertmanagers = append(h.alertmanagers, &alertmanagerSet{
 		ams: []alertmanager{
 			alertmanagerMock{