add Prometheus support

some basic counters and gauges are now exposed

api/api.go

@@ -19,6 +19,7 @@ const (
 	quotaScanPath         = "/api/v1/quota_scan"
 	userPath              = "/api/v1/user"
 	versionPath           = "/api/v1/version"
+	metricsPath           = "/metrics"
 )
 
 var (

api/api_test.go

@@ -36,6 +36,7 @@ const (
 	activeConnectionsPath = "/api/v1/connection"
 	quotaScanPath         = "/api/v1/quota_scan"
 	versionPath           = "/api/v1/version"
+	metricsPath           = "/metrics"
 )
 
 var (
@@ -710,6 +711,12 @@ func TestMethodNotAllowedMock(t *testing.T) {
 	checkResponseCode(t, http.StatusMethodNotAllowed, rr.Code)
 }
 
+func TestMetricsMock(t *testing.T) {
+	req, _ := http.NewRequest(http.MethodGet, metricsPath, nil)
+	rr := executeRequest(req)
+	checkResponseCode(t, http.StatusOK, rr.Code)
+}
+
 func waitTCPListening(address string) {
 	for {
 		conn, err := net.Dial("tcp", address)

api/router.go

@@ -9,6 +9,7 @@ import (
 	"github.com/go-chi/chi"
 	"github.com/go-chi/chi/middleware"
 	"github.com/go-chi/render"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
 // GetHTTPRouter returns the configured HTTP handler
@@ -31,6 +32,8 @@ func initializeRouter() {
 		sendAPIResponse(w, r, nil, "Method not allowed", http.StatusMethodNotAllowed)
 	}))
 
+	router.Handle(metricsPath, promhttp.Handler())
+
 	router.Get(versionPath, func(w http.ResponseWriter, r *http.Request) {
 		render.JSON(w, r, utils.GetAppVersion())
 	})