TUN-4698: Add cloudflared metrics endpoint to serve quick tunnel hostname

Author: Rishabh Bector

cmd/cloudflared/proxydns/cmd.go

@@ -73,7 +73,7 @@ func Run(c *cli.Context) error {
 		log.Fatal().Err(err).Msg("Failed to open the metrics listener")
 	}
 
-	go metrics.ServeMetrics(metricsListener, nil, nil, log)
+	go metrics.ServeMetrics(metricsListener, nil, nil, "", log)
 
 	listener, err := tunneldns.CreateListener(
 		c.String("address"),

cmd/cloudflared/tunnel/cmd.go

@@ -206,7 +206,7 @@ func runAdhocNamedTunnel(sc *subcommandContext, name, credentialsOutputPath stri
 
 // runClassicTunnel creates a "classic" non-named tunnel
 func runClassicTunnel(sc *subcommandContext) error {
-	return StartServer(sc.c, version, nil, sc.log, sc.isUIEnabled)
+	return StartServer(sc.c, version, nil, sc.log, sc.isUIEnabled, "")
 }
 
 func routeFromFlag(c *cli.Context) (route tunnelstore.Route, ok bool) {
@@ -225,6 +225,7 @@ func StartServer(
 	namedTunnel *connection.NamedTunnelConfig,
 	log *zerolog.Logger,
 	isUIEnabled bool,
+	quickTunnelHostname string,
 ) error {
 	_ = raven.SetDSN(sentryDSN)
 	var wg sync.WaitGroup
@@ -341,7 +342,7 @@ func StartServer(
 		defer wg.Done()
 		readinessServer := metrics.NewReadyServer(log)
 		observer.RegisterSink(readinessServer)
-		errC <- metrics.ServeMetrics(metricsListener, ctx.Done(), readinessServer, log)
+		errC <- metrics.ServeMetrics(metricsListener, ctx.Done(), readinessServer, quickTunnelHostname, log)
 	}()
 
 	if err := ingressRules.StartOrigins(&wg, log, ctx.Done(), errC); err != nil {

cmd/cloudflared/tunnel/quick_tunnel.go

@@ -64,6 +64,7 @@ func RunQuickTunnel(sc *subcommandContext) error {
 		&connection.NamedTunnelConfig{Credentials: credentials},
 		sc.log,
 		sc.isUIEnabled,
+		data.Result.Hostname,
 	)
 }
 

cmd/cloudflared/tunnel/subcommand_context.go

@@ -286,6 +286,7 @@ func (sc *subcommandContext) run(tunnelID uuid.UUID) error {
 		&connection.NamedTunnelConfig{Credentials: credentials},
 		sc.log,
 		sc.isUIEnabled,
+		"",
 	)
 }
 

metrics/metrics.go

@@ -22,7 +22,7 @@ const (
 	startupTime     = time.Millisecond * 500
 )
 
-func newMetricsHandler(readyServer *ReadyServer) *mux.Router {
+func newMetricsHandler(readyServer *ReadyServer, quickTunnelHostname string) *mux.Router {
 	router := mux.NewRouter()
 	router.PathPrefix("/debug/").Handler(http.DefaultServeMux)
 
@@ -33,6 +33,9 @@ func newMetricsHandler(readyServer *ReadyServer) *mux.Router {
 	if readyServer != nil {
 		router.Handle("/ready", readyServer)
 	}
+	router.HandleFunc("/quicktunnel", func(w http.ResponseWriter, r *http.Request) {
+		_, _ = fmt.Fprintf(w, `{"hostname":"%s"}`, quickTunnelHostname)
+	})
 
 	return router
 }
@@ -41,14 +44,15 @@ func ServeMetrics(
 	l net.Listener,
 	shutdownC <-chan struct{},
 	readyServer *ReadyServer,
+	quickTunnelHostname string,
 	log *zerolog.Logger,
 ) (err error) {
 	var wg sync.WaitGroup
 	// Metrics port is privileged, so no need for further access control
 	trace.AuthRequest = func(*http.Request) (bool, bool) { return true, true }
 	// TODO: parameterize ReadTimeout and WriteTimeout. The maximum time we can
 	// profile CPU usage depends on WriteTimeout
-	h := newMetricsHandler(readyServer)
+	h := newMetricsHandler(readyServer, quickTunnelHostname)
 	server := &http.Server{
 		ReadTimeout:  10 * time.Second,
 		WriteTimeout: 10 * time.Second,