Do not require "experimental" for metrics API

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cmd/dockerd/daemon.go

@@ -204,8 +204,8 @@ func (cli *DaemonCli) start(opts *daemonOptions) (err error) {
 
 	cli.d = d
 
-	if err := cli.startMetricsServer(cli.Config.MetricsAddress); err != nil {
-		return err
+	if err := startMetricsServer(cli.Config.MetricsAddress); err != nil {
+		return errors.Wrap(err, "failed to start metrics server")
 	}
 
 	c, err := createAndStartCluster(cli, d)

cmd/dockerd/metrics.go

@@ -3,21 +3,16 @@ package main
 import (
 	"net"
 	"net/http"
+	"strings"
 
 	metrics "github.com/docker/go-metrics"
-	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 )
 
-func (cli *DaemonCli) startMetricsServer(addr string) error {
+func startMetricsServer(addr string) error {
 	if addr == "" {
 		return nil
 	}
-
-	if !cli.d.HasExperimental() {
-		return errors.New("metrics-addr is only supported when experimental is enabled")
-	}
-
 	if err := allocateDaemonPort(addr); err != nil {
 		return err
 	}
@@ -28,8 +23,9 @@ func (cli *DaemonCli) startMetricsServer(addr string) error {
 	mux := http.NewServeMux()
 	mux.Handle("/metrics", metrics.Handler())
 	go func() {
-		if err := http.Serve(l, mux); err != nil {
-			logrus.Errorf("serve metrics api: %s", err)
+		logrus.Infof("metrics API listening on %s", l.Addr())
+		if err := http.Serve(l, mux); err != nil && !strings.Contains(err.Error(), "use of closed network connection") {
+			logrus.WithError(err).Error("error serving metrics API")
 		}
 	}()
 	return nil

daemon/metrics_unix.go

@@ -6,6 +6,7 @@ import (
 	"net"
 	"net/http"
 	"path/filepath"
+	"strings"
 
 	"github.com/docker/docker/pkg/plugingetter"
 	"github.com/docker/docker/pkg/plugins"
@@ -28,7 +29,10 @@ func (daemon *Daemon) listenMetricsSock() (string, error) {
 	mux := http.NewServeMux()
 	mux.Handle("/metrics", metrics.Handler())
 	go func() {
-		http.Serve(l, mux)
+		logrus.Debugf("metrics API listening on %s", l.Addr())
+		if err := http.Serve(l, mux); err != nil && !strings.Contains(err.Error(), "use of closed network connection") {
+			logrus.WithError(err).Error("error serving metrics API")
+		}
 	}()
 	daemon.metricsPluginListener = l
 	return path, nil