⚠️ metrics are now on by default

Author: Mengqi Yu

pkg/manager/internal.go

@@ -230,17 +230,19 @@ func (cm *controllerManager) GetWebhookServer() *webhook.Server {
 }
 
 func (cm *controllerManager) serveMetrics(stop <-chan struct{}) {
+	var metricsPath = "/metrics"
 	handler := promhttp.HandlerFor(metrics.Registry, promhttp.HandlerOpts{
 		ErrorHandling: promhttp.HTTPErrorOnError,
 	})
 	// TODO(JoelSpeed): Use existing Kubernetes machinery for serving metrics
 	mux := http.NewServeMux()
-	mux.Handle("/metrics", handler)
+	mux.Handle(metricsPath, handler)
 	server := http.Server{
 		Handler: mux,
 	}
 	// Run the server
 	go func() {
+		log.Info("starting metrics server", "path", metricsPath)
 		if err := server.Serve(cm.metricsListener); err != nil && err != http.ErrServerClosed {
 			cm.errChan <- err
 		}

pkg/manager/manager.go

@@ -135,7 +135,8 @@ type Options struct {
 	Namespace string
 
 	// MetricsBindAddress is the TCP address that the controller should bind to
-	// for serving prometheus metrics
+	// for serving prometheus metrics.
+	// It can be set to "0" to disable the metrics serving.
 	MetricsBindAddress string
 
 	// Port is the port that the webhook server serves at.

pkg/metrics/listener.go

@@ -21,11 +21,9 @@ import (
 	"net"
 )
 
-// DefaultBindAddress sets the default bind address for the metrics
-// listener
-// The metrics is off by default.
-// TODO: Flip the default by changing DefaultBindAddress back to ":8080" in the v0.2.0.
-var DefaultBindAddress = "0"
+// DefaultBindAddress sets the default bind address for the metrics listener
+// The metrics is on by default.
+var DefaultBindAddress = ":8080"
 
 // NewListener creates a new TCP listener bound to the given address.
 func NewListener(addr string) (net.Listener, error) {
@@ -39,9 +37,12 @@ func NewListener(addr string) (net.Listener, error) {
 		return nil, nil
 	}
 
+	log.Info("metrics server is starting to listen", "addr", addr)
 	ln, err := net.Listen("tcp", addr)
 	if err != nil {
-		return nil, fmt.Errorf("error listening on %s: %v", addr, err)
+		er := fmt.Errorf("error listening on %s: %v", addr, err)
+		log.Error(er, "metrics server failed to listen. You may want to disable the metrics server or use another port if it is due to conflicts")
+		return nil, er
 	}
 	return ln, nil
 }