[#373] metrics: Move labels to consts

To unify label naming all lable keys and other consts are moved to
one file.

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/metrics/morph.go

@@ -9,15 +9,6 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-const (
-	morphSubsystem             = "morph"
-	morphNotificationTypeLabel = "notification_type"
-	morphInvokeTypeLabel       = "invoke_type"
-	morphContractLabel         = "contract"
-	morphMethodLabel           = "method"
-	morphSuccessLabel          = "success"
-)
-
 type morphClientMetrics struct {
 	switchCount       prometheus.Counter
 	lastBlock         prometheus.Gauge
@@ -44,13 +35,13 @@ func NewMorphClientMetrics() morphmetrics.Register {
 			Subsystem: morphSubsystem,
 			Name:      "notifications_total",
 			Help:      "Number of notifications received by notification type",
-		}, []string{morphNotificationTypeLabel}),
+		}, []string{notificationTypeLabel}),
 		invokeDuration: metrics.NewHistogramVec(prometheus.HistogramOpts{
 			Namespace: namespace,
 			Subsystem: morphSubsystem,
 			Name:      "invoke_duration_seconds",
 			Help:      "Cummulative duration of contract invocations",
-		}, []string{morphInvokeTypeLabel, morphContractLabel, morphMethodLabel, morphSuccessLabel}),
+		}, []string{invokeTypeLabel, contractLabel, methodLabel, successLabel}),
 	}
 }
 
@@ -65,7 +56,7 @@ func (m *morphClientMetrics) SetLastBlock(index uint32) {
 func (m *morphClientMetrics) IncNotificationCount(typ string) {
 	m.notificationCount.With(
 		prometheus.Labels{
-			morphNotificationTypeLabel: typ,
+			notificationTypeLabel: typ,
 		},
 	).Inc()
 }
@@ -73,10 +64,10 @@ func (m *morphClientMetrics) IncNotificationCount(typ string) {
 func (m *morphClientMetrics) ObserveInvoke(typ string, contract string, method string, success bool, d time.Duration) {
 	m.invokeDuration.With(
 		prometheus.Labels{
-			morphInvokeTypeLabel: typ,
-			morphContractLabel:   contract,
-			morphMethodLabel:     method,
-			morphSuccessLabel:    strconv.FormatBool(success),
+			invokeTypeLabel: typ,
+			contractLabel:   contract,
+			methodLabel:     method,
+			successLabel:    strconv.FormatBool(success),
 		},
 	).Observe(d.Seconds())
 }