Move metric definition to the same file as other metrics (#424)

httpapi/config.go

@@ -6,15 +6,10 @@ import (
 	"time"
 
 	"github.com/julienschmidt/httprouter"
-	"github.com/prometheus/client_golang/prometheus"
 	"github.com/serverless/event-gateway/function"
 	"github.com/serverless/event-gateway/subscription"
 )
 
-func init() {
-	prometheus.MustRegister(requestDuration)
-}
-
 // StartConfigAPI creates a new configuration API server and listens for requests.
 func StartConfigAPI(functions function.Service, subscriptions subscription.Service, config ServerConfig) {
 	router := httprouter.New()
@@ -43,21 +38,12 @@ func StartConfigAPI(functions function.Service, subscriptions subscription.Servi
 	}()
 }
 
-var requestDuration = prometheus.NewHistogram(
-	prometheus.HistogramOpts{
-		Namespace: "gateway",
-		Subsystem: "config",
-		Name:      "request_duration_seconds",
-		Help:      "Bucketed histogram of request duration of Config API requests",
-		Buckets:   prometheus.ExponentialBuckets(0.0005, 2, 16),
-	})
-
 type metricsReporter struct {
 	Handler http.Handler
 }
 
 func (m metricsReporter) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	start := time.Now()
 	m.Handler.ServeHTTP(w, r)
-	requestDuration.Observe(time.Since(start).Seconds())
+	metricConfigRequestDuration.Observe(time.Since(start).Seconds())
 }

httpapi/metrics.go

@@ -9,6 +9,7 @@ func init() {
 	prometheus.MustRegister(metricSubscriptions)
 
 	prometheus.MustRegister(metricConfigRequests)
+	prometheus.MustRegister(metricConfigRequestDuration)
 }
 
 // Functions
@@ -40,3 +41,12 @@ var metricConfigRequests = prometheus.NewCounterVec(
 		Name:      "requests_total",
 		Help:      "Total of Config API requests.",
 	}, []string{"space", "resource", "operation"})
+
+var metricConfigRequestDuration = prometheus.NewHistogram(
+	prometheus.HistogramOpts{
+		Namespace: "gateway",
+		Subsystem: "config",
+		Name:      "request_duration_seconds",
+		Help:      "Bucketed histogram of request duration of Config API requests",
+		Buckets:   prometheus.ExponentialBuckets(0.0005, 2, 16),
+	})