Add a method label to the in-flight HTTP requests

Signed-off-by: Douglas Camata <[email protected]>

pkg/extprom/http/instrument_server.go

@@ -61,8 +61,8 @@ func (ins *defaultInstrumentationMiddleware) NewHandler(handlerName string, hand
 func httpInstrumentationHandler(baseLabels prometheus.Labels, metrics *defaultMetrics, next http.Handler) http.HandlerFunc {
 	return promhttp.InstrumentHandlerRequestSize(
 		metrics.requestSize.MustCurryWith(baseLabels),
-		promhttp.InstrumentHandlerInFlight(
-			metrics.inflightHTTPRequests.With(baseLabels),
+		instrumentHandlerInFlight(
+			metrics.inflightHTTPRequests.MustCurryWith(baseLabels),
 			promhttp.InstrumentHandlerCounter(
 				metrics.requestsTotal.MustCurryWith(baseLabels),
 				promhttp.InstrumentHandlerResponseSize(
@@ -129,11 +129,16 @@ func (wd *responseWriterDelegator) Status() string {
 	return fmt.Sprintf("%d", wd.StatusCode())
 }
 
-// NewInstrumentHandlerInflightTenant creates a middleware used to export the current amount of concurrent requests
-// being handled. It has an optional tenant label whenever a tenant is present in the context.
-func NewInstrumentHandlerInflightTenant(gaugeVec *prometheus.GaugeVec, tenantHeader string, next http.HandlerFunc) http.HandlerFunc {
-	return func(w http.ResponseWriter, r *http.Request) {
-		tenant := r.Header.Get(tenantHeader)
-		promhttp.InstrumentHandlerInFlight(gaugeVec.With(prometheus.Labels{"tenant": tenant}), next).ServeHTTP(w, r)
-	}
+// instrumentHandlerInFlight is responsible for counting the amount of
+// in-flight HTTP requests (requests being processed by the handler) at a given
+// moment in time.
+// This is used instead of prometheus/client_golang/promhttp.InstrumentHandlerInFlight
+// to be able to have the HTTP method as a label.
+func instrumentHandlerInFlight(vec *prometheus.GaugeVec, next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gauge := vec.With(prometheus.Labels{"method": r.Method})
+		gauge.Inc()
+		defer gauge.Dec()
+		next.ServeHTTP(w, r)
+	})
 }

pkg/extprom/http/metrics.go

@@ -60,7 +60,7 @@ func newDefaultMetrics(reg prometheus.Registerer, buckets []float64, extraLabels
 				Name: "http_inflight_requests",
 				Help: "Current number of HTTP requests the handler is responding to.",
 			},
-			append([]string{"handler"}, extraLabels...),
+			append([]string{"handler", "method"}, extraLabels...),
 		),
 	}
 }