[#374] Add inner-ring event metrics

Signed-off-by: Alejandro Lopez <a.lopez@yadro.com>

pkg/metrics/innerring.go

@@ -1,13 +1,23 @@
 package metrics
 
-import "github.com/prometheus/client_golang/prometheus"
+import (
+	"strconv"
+	"time"
 
-const innerRingSubsystem = "ir"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const (
+	innerRingSubsystem    = "ir"
+	innerRingLabelSuccess = "success"
+	innerRingLabelType    = "type"
+)
 
 // InnerRingServiceMetrics contains metrics collected by inner ring.
 type InnerRingServiceMetrics struct {
-	epoch  metric[prometheus.Gauge]
-	health metric[prometheus.Gauge]
+	epoch         metric[prometheus.Gauge]
+	health        metric[prometheus.Gauge]
+	eventDuration metric[*prometheus.HistogramVec]
 }
 
 // NewInnerRingMetrics returns new instance of metrics collectors for inner ring.
@@ -25,14 +35,22 @@ func NewInnerRingMetrics() *InnerRingServiceMetrics {
 			Name:      "health",
 			Help:      "Current inner-ring node state.",
 		})
+		eventDuration = newHistogramVec(prometheus.HistogramOpts{
+			Namespace: namespace,
+			Subsystem: innerRingSubsystem,
+			Name:      "event_duration_seconds",
+			Help:      "Duration of processing of inner-ring events",
+		}, []string{innerRingLabelType, innerRingLabelSuccess})
 	)
 
 	mustRegister(epoch)
 	mustRegister(health)
+	mustRegister(eventDuration)
 
 	return &InnerRingServiceMetrics{
-		epoch:  epoch,
-		health: health,
+		epoch:         epoch,
+		health:        health,
+		eventDuration: eventDuration,
 	}
 }
 
@@ -45,3 +63,10 @@ func (m InnerRingServiceMetrics) SetEpoch(epoch uint64) {
 func (m InnerRingServiceMetrics) SetHealth(s int32) {
 	m.health.value.Set(float64(s))
 }
+
+func (m InnerRingServiceMetrics) AddEvent(d time.Duration, typ string, success bool) {
+	m.eventDuration.value.With(prometheus.Labels{
+		innerRingLabelType:    typ,
+		innerRingLabelSuccess: strconv.FormatBool(success),
+	}).Observe(d.Seconds())
+}