cleaning functionalities, adding arguments at start

app/Prometheus/utils.go

@@ -3,6 +3,9 @@ package prometheus
 
 import (
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/collectors"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"net/http"
 )
 
 // Metrics structure for storing counter
@@ -12,11 +15,36 @@ type Metrics struct {
 }
 
 var (
-	//HTTPCounter Metrics
-	HTTPCounter = InitializeHTTPReqCounter(Reg)
-	Reg         = prometheus.NewRegistry()
+	// HTTPCounter Metrics
+	HTTPCounter = initializeHTTPReqCounter()
+	// Reg is a custom registry to have more control on metrics exported.
+	Reg = prometheus.NewRegistry()
+	// MetricsEnabled is the flag used to enable the prometheus metrics backend.
+	MetricsEnabled = false
 )
 
+// InitMetrics enable the metrics functionality if the flags is passed as an argument
+func InitMetrics(m bool) {
+	if m {
+		MetricsEnabled = true
+		initPrometheusRegistry()
+		// Define custom promhttp handler that expose just our custom registry.
+		http.Handle("/metrics", promhttp.HandlerFor(Reg, promhttp.HandlerOpts{
+			EnableOpenMetrics: true,
+			Registry:          Reg,
+		}))
+	}
+}
+
+// InitPrometheusRegistry initialize registry and counters if metrics flag pass as argument.
+func initPrometheusRegistry() {
+	// We use a custom registry to better now what metrics are exposed.
+	Reg = prometheus.NewRegistry()
+	Reg.MustRegister(HTTPCounter.ClientHTTPReqs)
+	Reg.MustRegister(HTTPCounter.BackendHTTPReqs)
+	Reg.MustRegister(collectors.NewBuildInfoCollector())
+}
+
 // IncrementClientCounterVec increments the counter with method label provided.
 func IncrementClientCounterVec(m string) {
 	HTTPCounter.ClientHTTPReqs.WithLabelValues(m).Inc()
@@ -30,7 +58,7 @@ func IncrementBackendCounterVec(m string) {
 }
 
 // InitializeHTTPReqCounter inits the httpReqs counter that will be exported.
-func InitializeHTTPReqCounter(reg prometheus.Registerer) *Metrics {
+func initializeHTTPReqCounter() *Metrics {
 	HTTPCounters := &Metrics{
 		ClientHTTPReqs: prometheus.NewCounterVec(prometheus.CounterOpts{
 			Name: "client_http_requests_total",