Add basic prometheus support

This adds a metrics packages that creates additional metrics.  Add the
metrics endpoint to the docker api server under `/metrics`.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

Add metrics to daemon package

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

api: use standard way for metrics route

Also add "type" query parameter

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

Convert timers to ms

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
Upstream-commit: 3343d234f3b131d4be1d4ca84385e184633a79bd
Component: engine

components/engine/cmd/dockerd/daemon.go

@@ -248,6 +248,15 @@ func (cli *DaemonCli) start(opts daemonOptions) (err error) {
 		return fmt.Errorf("Error starting daemon: %v", err)
 	}
 
+	if cli.Config.MetricsAddress != "" {
+		if !d.HasExperimental() {
+			return fmt.Errorf("metrics-addr is only supported when experimental is enabled")
+		}
+		if err := startMetricsServer(cli.Config.MetricsAddress); err != nil {
+			return err
+		}
+	}
+
 	name, _ := os.Hostname()
 
 	c, err := cluster.New(cluster.Config{

components/engine/cmd/dockerd/metrics.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"net"
+	"net/http"
+
+	"github.com/Sirupsen/logrus"
+	metrics "github.com/docker/go-metrics"
+)
+
+func startMetricsServer(addr string) error {
+	if err := allocateDaemonPort(addr); err != nil {
+		return err
+	}
+	l, err := net.Listen("tcp", addr)
+	if err != nil {
+		return err
+	}
+	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)
+		}
+	}()
+	return nil
+}