feat: add instrumentation

main.go

@@ -8,6 +8,9 @@ import (
 	"net/http"
 	"os"
 
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+
 	"github.com/urfave/cli/v2"
 )
 
@@ -50,17 +53,16 @@ func startServer(ctx context.Context, d *daemon, tcpListener string) error {
 		return err
 	}
 
+	log.Printf("listening on %v\n", l.Addr())
+	log.Printf("Libp2p host peer id %s\n", d.h.ID())
+	log.Printf("Libp2p host listening on %v\n", d.h.Addrs())
 	log.Printf("listening on %v\n", l.Addr())
 
 	d.mustStart()
 
 	log.Printf("ready to start serving")
 
-	// 1. Is the peer findable in the DHT?
-	// 2. Does the multiaddr work? If not, what's the error?
-	// 3. Is the CID in the DHT?
-	// 4. Does the peer respond that it has the given data over Bitswap?
-	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+	checkHandler := func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Add("Access-Control-Allow-Origin", "*")
 		data, err := d.runCheck(r.URL.Query())
 		if err == nil {
@@ -70,8 +72,60 @@ func startServer(ctx context.Context, d *daemon, tcpListener string) error {
 			w.WriteHeader(http.StatusInternalServerError)
 			_, _ = w.Write([]byte(err.Error()))
 		}
+	}
+
+	// Create a custom registry
+	reg := prometheus.NewRegistry()
+
+	requestsTotal := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "http_requests_total",
+			Help: "Total number of slow requests",
+		},
+		[]string{"code"},
+	)
+
+	requestDuration := prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Name:    "http_request_duration_seconds",
+			Help:    "Duration of slow requests",
+			Buckets: prometheus.DefBuckets,
+		},
+		[]string{"code"},
+	)
+
+	requestsInFlight := prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "slow_requests_in_flight",
+		Help: "Number of slow requests currently being served",
 	})
 
+	// Register metrics with our custom registry
+	reg.MustRegister(requestsTotal)
+	reg.MustRegister(requestDuration)
+	reg.MustRegister(requestsInFlight)
+	// Instrument the slowHandler
+	instrumentedHandler := promhttp.InstrumentHandlerCounter(
+		requestsTotal,
+		promhttp.InstrumentHandlerDuration(
+			requestDuration,
+			promhttp.InstrumentHandlerInFlight(
+				requestsInFlight,
+				http.HandlerFunc(checkHandler),
+			),
+		),
+	)
+
+	// 1. Is the peer findable in the DHT?
+	// 2. Does the multiaddr work? If not, what's the error?
+	// 3. Is the CID in the DHT?
+	// 4. Does the peer respond that it has the given data over Bitswap?
+	http.Handle("/check", instrumentedHandler)
+	http.Handle("/debug/libp2p", promhttp.Handler())
+	http.Handle("/debug/http", promhttp.HandlerFor(
+		reg,
+		promhttp.HandlerOpts{},
+	))
+
 	done := make(chan error, 1)
 	go func() {
 		defer close(done)