etcd: support v2 leader endpoint

etcd/etcd.go

@@ -22,6 +22,7 @@ const (
 	v2machineKVPrefix = "/_etcd/machines"
 	v2Prefix          = "/v2/keys"
 	v2machinePrefix   = "/v2/machines"
+	v2LeaderPrefix    = "/v2/leader"
 
 	raftPrefix = "/raft"
 )
@@ -77,6 +78,7 @@ func New(c *config.Config, id int) *Server {
 	m.Handle(v2Prefix+"/", handlerErr(s.serveValue))
 	m.Handle("/raft", s.t)
 	m.Handle(v2machinePrefix, handlerErr(s.serveMachines))
+	m.Handle(v2LeaderPrefix, handlerErr(s.serveLeader))
 	s.Handler = m
 	return s
 }

etcd/v2_http.go

@@ -43,6 +43,17 @@ func (s *Server) serveMachines(w http.ResponseWriter, r *http.Request) error {
 	return nil
 }
 
+func (s *Server) serveLeader(w http.ResponseWriter, r *http.Request) error {
+	if r.Method != "GET" {
+		return allow(w, "GET")
+	}
+	if laddr, ok := s.t.urls[s.node.Leader()]; ok {
+		w.Write([]byte(laddr))
+		return nil
+	}
+	return fmt.Errorf("no leader")
+}
+
 type handlerErr func(w http.ResponseWriter, r *http.Request) error
 
 func (eh handlerErr) ServeHTTP(w http.ResponseWriter, r *http.Request) {

etcd/v2_http_endpoint_test.go

@@ -42,3 +42,40 @@ func TestMachinesEndPoint(t *testing.T) {
 	}
 	afterTest(t)
 }
+
+func TestLeaderEndPoint(t *testing.T) {
+	es, hs := buildCluster(3)
+	waitCluster(t, es)
+
+	us := make([]string, len(hs))
+	for i := range hs {
+		us[i] = hs[i].URL
+	}
+	// todo(xiangli) change this to raft port...
+	w := hs[0].URL + "/raft"
+
+	for i := range hs {
+		r, err := http.Get(hs[i].URL + v2LeaderPrefix)
+		if err != nil {
+			t.Errorf("%v", err)
+			break
+		}
+		b, err := ioutil.ReadAll(r.Body)
+		r.Body.Close()
+		if err != nil {
+			t.Errorf("%v", err)
+			break
+		}
+		if string(b) != w {
+			t.Errorf("leader = %v, want %v", string(b), w)
+		}
+	}
+
+	for i := range es {
+		es[len(es)-i-1].Stop()
+	}
+	for i := range hs {
+		hs[len(hs)-i-1].Close()
+	}
+	afterTest(t)
+}