embed: configure 'ListenMetricsUrls'

Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>

embed/config.go

@@ -112,10 +112,12 @@ type Config struct {
 
 	// debug
 
-	Debug        bool   `json:"debug"`
-	LogPkgLevels string `json:"log-package-levels"`
-	EnablePprof  bool
-	Metrics      string `json:"metrics"`
+	Debug                 bool   `json:"debug"`
+	LogPkgLevels          string `json:"log-package-levels"`
+	EnablePprof           bool
+	Metrics               string `json:"metrics"`
+	ListenMetricsUrls     []url.URL
+	ListenMetricsUrlsJSON string `json:"listen-metrics-urls"`
 
 	// ForceNewCluster starts a new cluster even if previously started; unsafe.
 	ForceNewCluster bool `json:"force-new-cluster"`
@@ -255,6 +257,14 @@ func (cfg *configYAML) configFromFile(path string) error {
 		cfg.ACUrls = []url.URL(u)
 	}
 
+	if cfg.ListenMetricsUrlsJSON != "" {
+		u, err := types.NewURLs(strings.Split(cfg.ListenMetricsUrlsJSON, ","))
+		if err != nil {
+			plog.Fatalf("unexpected error setting up listen-metrics-urls: %v", err)
+		}
+		cfg.ListenMetricsUrls = []url.URL(u)
+	}
+
 	// If a discovery flag is set, clear default initial cluster set by InitialClusterFromName
 	if (cfg.Durl != "" || cfg.DNSCluster != "") && cfg.InitialCluster == defaultInitialCluster {
 		cfg.InitialCluster = ""
@@ -285,6 +295,9 @@ func (cfg *Config) Validate() error {
 	if err := checkBindURLs(cfg.LCUrls); err != nil {
 		return err
 	}
+	if err := checkBindURLs(cfg.ListenMetricsUrls); err != nil {
+		return err
+	}
 
 	// Check if conflicting flags are passed.
 	nSet := 0

embed/etcd.go

@@ -21,6 +21,7 @@ import (
 	defaultLog "log"
 	"net"
 	"net/http"
+	"net/url"
 	"path/filepath"
 	"sync"
 	"time"
@@ -35,6 +36,7 @@ import (
 	"github.com/coreos/etcd/pkg/types"
 	"github.com/coreos/etcd/rafthttp"
 	"github.com/coreos/pkg/capnslog"
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 var plog = capnslog.NewPackageLogger("github.com/coreos/etcd", "embed")
@@ -55,9 +57,10 @@ const (
 
 // Etcd contains a running etcd server and its listeners.
 type Etcd struct {
-	Peers   []*peerListener
-	Clients []net.Listener
-	Server  *etcdserver.EtcdServer
+	Peers            []*peerListener
+	Clients          []net.Listener
+	metricsListeners []net.Listener
+	Server           *etcdserver.EtcdServer
 
 	cfg   Config
 	stopc chan struct{}
@@ -205,6 +208,11 @@ func (e *Etcd) Close() {
 			e.Clients[i].Close()
 		}
 	}
+	for i := range e.metricsListeners {
+		if e.metricsListeners[i] != nil {
+			e.metricsListeners[i].Close()
+		}
+	}
 
 	// close rafthttp transports
 	if e.Server != nil {
@@ -400,6 +408,29 @@ func (e *Etcd) serve() (err error) {
 			e.errHandler(s.serve(e.Server, &e.cfg.ClientTLSInfo, h, e.errHandler))
 		}(sctx)
 	}
+
+	if len(e.cfg.ListenMetricsUrls) > 0 {
+		// TODO: maybe etcdhttp.MetricsPath or get the path from the user-provided URL
+		metricsMux := http.NewServeMux()
+		metricsMux.Handle("/metrics", prometheus.Handler())
+
+		for _, murl := range e.cfg.ListenMetricsUrls {
+			if murl.Scheme == "https" {
+				murl.Scheme = "http"
+				plog.Warningf("serving non-secured '/metrics' for %s", murl.String())
+			}
+			ml, err := transport.NewListener(murl.Host, murl.Scheme, nil)
+			if err != nil {
+				return err
+			}
+			e.metricsListeners = append(e.metricsListeners, ml)
+			go func(u url.URL, ln net.Listener) {
+				plog.Info("listening for metrics on ", u.String())
+				e.errHandler(http.Serve(ln, metricsMux))
+			}(murl, ml)
+		}
+	}
+
 	return nil
 }