exp/lighthorizon: Add metrics middleware to collect request duration metrics

exp/lighthorizon/http.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"github.com/go-chi/chi"
+	"github.com/go-chi/chi/middleware"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/stellar/go/exp/lighthorizon/actions"
+	"github.com/stellar/go/exp/lighthorizon/services"
+	"net/http"
+	"strconv"
+	"time"
+)
+
+func newWrapResponseWriter(w http.ResponseWriter, r *http.Request) middleware.WrapResponseWriter {
+	mw, ok := w.(middleware.WrapResponseWriter)
+	if !ok {
+		mw = middleware.NewWrapResponseWriter(w, r.ProtoMajor)
+	}
+
+	return mw
+}
+
+func prometheusMiddleware(requestDurationMetric *prometheus.SummaryVec) func(next http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			mw := newWrapResponseWriter(w, r)
+
+			then := time.Now()
+			next.ServeHTTP(mw, r)
+			duration := time.Since(then)
+
+			requestDurationMetric.With(prometheus.Labels{
+				"status": strconv.FormatInt(int64(mw.Status()), 10),
+				"method": r.Method,
+			}).Observe(float64(duration.Seconds()))
+		})
+	}
+}
+
+func lightHorizonHTTPHandler(registry *prometheus.Registry, lightHorizon services.LightHorizon) http.Handler {
+	requestDurationMetric := prometheus.NewSummaryVec(
+		prometheus.SummaryOpts{
+			Namespace: "horizon_lite", Subsystem: "http", Name: "requests_duration_seconds",
+			Help: "HTTP requests durations, sliding window = 10m",
+		},
+		[]string{"status", "method"},
+	)
+	registry.MustRegister(requestDurationMetric)
+
+	router := chi.NewMux()
+	router.Use(prometheusMiddleware(requestDurationMetric))
+
+	router.Route("/accounts/{account_id}", func(r chi.Router) {
+		r.MethodFunc(http.MethodGet, "/transactions", actions.NewTXByAccountHandler(lightHorizon))
+		r.MethodFunc(http.MethodGet, "/operations", actions.NewOpsByAccountHandler(lightHorizon))
+	})
+
+	router.MethodFunc(http.MethodGet, "/", actions.ApiDocs())
+	router.Method(http.MethodGet, "/metrics", promhttp.HandlerFor(registry, promhttp.HandlerOpts{}))
+
+	return router
+}

exp/lighthorizon/main.go

@@ -4,11 +4,7 @@ import (
 	"flag"
 	"net/http"
 
-	"github.com/go-chi/chi"
 	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promhttp"
-
-	"github.com/stellar/go/exp/lighthorizon/actions"
 	"github.com/stellar/go/exp/lighthorizon/archive"
 	"github.com/stellar/go/exp/lighthorizon/index"
 	"github.com/stellar/go/exp/lighthorizon/services"
@@ -71,14 +67,5 @@ if left empty, uses a temporary directory`)
 		},
 	}
 
-	router := chi.NewMux()
-	router.Route("/accounts/{account_id}", func(r chi.Router) {
-		r.MethodFunc(http.MethodGet, "/transactions", actions.NewTXByAccountHandler(lightHorizon))
-		r.MethodFunc(http.MethodGet, "/operations", actions.NewOpsByAccountHandler(lightHorizon))
-	})
-
-	router.MethodFunc(http.MethodGet, "/", actions.ApiDocs())
-	router.Method(http.MethodGet, "/metrics", promhttp.HandlerFor(registry, promhttp.HandlerOpts{}))
-
-	log.Fatal(http.ListenAndServe(":8080", router))
+	log.Fatal(http.ListenAndServe(":8080", lightHorizonHTTPHandler(registry, lightHorizon)))
 }