web: add 'code' label to HTTP metrics (#5640)

* web: add prometheus_http_requests_total metrics

Signed-off-by: Simon Pasquier <spasquie@redhat.com>

* Add unit test for requestCounter metric

Signed-off-by: Simon Pasquier <spasquie@redhat.com>

web/web.go

@@ -90,6 +90,13 @@ func withStackTracer(h http.Handler, l log.Logger) http.Handler {
 }
 
 var (
+	requestCounter = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "prometheus_http_requests_total",
+			Help: "Counter of HTTP requests.",
+		},
+		[]string{"handler", "code"},
+	)
 	requestDuration = prometheus.NewHistogramVec(
 		prometheus.HistogramOpts{
 			Name:    "prometheus_http_request_duration_seconds",
@@ -109,7 +116,7 @@ var (
 )
 
 func init() {
-	prometheus.MustRegister(requestDuration, responseSize)
+	prometheus.MustRegister(requestCounter, requestDuration, responseSize)
 }
 
 // Handler serves various HTTP endpoints of the Prometheus server
@@ -199,11 +206,14 @@ func instrumentHandlerWithPrefix(prefix string) func(handlerName string, handler
 }
 
 func instrumentHandler(handlerName string, handler http.HandlerFunc) http.HandlerFunc {
-	return promhttp.InstrumentHandlerDuration(
-		requestDuration.MustCurryWith(prometheus.Labels{"handler": handlerName}),
-		promhttp.InstrumentHandlerResponseSize(
-			responseSize.MustCurryWith(prometheus.Labels{"handler": handlerName}),
-			handler,
+	return promhttp.InstrumentHandlerCounter(
+		requestCounter.MustCurryWith(prometheus.Labels{"handler": handlerName}),
+		promhttp.InstrumentHandlerDuration(
+			requestDuration.MustCurryWith(prometheus.Labels{"handler": handlerName}),
+			promhttp.InstrumentHandlerResponseSize(
+				responseSize.MustCurryWith(prometheus.Labels{"handler": handlerName}),
+				handler,
+			),
 		),
 	)
 }

web/web_test.go

@@ -21,10 +21,13 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"os"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
 
+	prom_testutil "github.com/prometheus/client_golang/prometheus/testutil"
+
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/notifier"
 	"github.com/prometheus/prometheus/rules"
@@ -402,3 +405,31 @@ func TestDebugHandler(t *testing.T) {
 		testutil.Equals(t, tc.code, w.Code)
 	}
 }
+
+func TestHTTPMetrics(t *testing.T) {
+	t.Parallel()
+
+	handler := New(nil, &Options{RoutePrefix: "/"})
+	getReady := func() int {
+		t.Helper()
+		w := httptest.NewRecorder()
+
+		req, err := http.NewRequest("GET", "/-/ready", nil)
+		testutil.Ok(t, err)
+
+		handler.router.ServeHTTP(w, req)
+		return w.Code
+	}
+
+	code := getReady()
+	testutil.Equals(t, http.StatusServiceUnavailable, code)
+	testutil.Equals(t, 1, int(prom_testutil.ToFloat64(requestCounter.WithLabelValues("/-/ready", strconv.Itoa(http.StatusServiceUnavailable)))))
+
+	handler.Ready()
+	for range [2]int{} {
+		code = getReady()
+		testutil.Equals(t, http.StatusOK, code)
+	}
+	testutil.Equals(t, 2, int(prom_testutil.ToFloat64(requestCounter.WithLabelValues("/-/ready", strconv.Itoa(http.StatusOK)))))
+	testutil.Equals(t, 1, int(prom_testutil.ToFloat64(requestCounter.WithLabelValues("/-/ready", strconv.Itoa(http.StatusServiceUnavailable)))))
+}