v2http: put back /v2/machines and mark as non-deprecated

This reverts commit 2bb33181b6c8fbe8109fc668a19ce4ab46c605ec. python-etcd
seems to depend on /v2/machines and the maintainer vanished. Plus, it is
prefixed with /v2/ so it probably can't be deprecated anyway.

etcdserver/api/v2http/client.go

@@ -46,15 +46,16 @@ import (
 )
 
 const (
-	authPrefix    = "/v2/auth"
-	keysPrefix    = "/v2/keys"
-	membersPrefix = "/v2/members"
-	statsPrefix   = "/v2/stats"
-	varsPath      = "/debug/vars"
-	metricsPath   = "/metrics"
-	healthPath    = "/health"
-	versionPath   = "/version"
-	configPath    = "/config"
+	authPrefix     = "/v2/auth"
+	keysPrefix     = "/v2/keys"
+	machinesPrefix = "/v2/machines"
+	membersPrefix  = "/v2/members"
+	statsPrefix    = "/v2/stats"
+	varsPath       = "/debug/vars"
+	metricsPath    = "/metrics"
+	healthPath     = "/health"
+	versionPath    = "/version"
+	configPath     = "/config"
 )
 
 // NewClientHandler generates a muxed http.Handler with the given parameters to serve etcd client requests.
@@ -83,6 +84,8 @@ func NewClientHandler(server *etcdserver.EtcdServer, timeout time.Duration) http
 		clientCertAuthEnabled: server.Cfg.ClientCertAuthEnabled,
 	}
 
+	mah := &machinesHandler{cluster: server.Cluster()}
+
 	sech := &authHandler{
 		sec:                   sec,
 		cluster:               server.Cluster(),
@@ -103,6 +106,7 @@ func NewClientHandler(server *etcdserver.EtcdServer, timeout time.Duration) http
 	mux.Handle(metricsPath, prometheus.Handler())
 	mux.Handle(membersPrefix, mh)
 	mux.Handle(membersPrefix+"/", mh)
+	mux.Handle(machinesPrefix, mah)
 	handleAuth(mux, sech)
 
 	return requestLogger(mux)
@@ -164,6 +168,18 @@ func (h *keysHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+type machinesHandler struct {
+	cluster api.Cluster
+}
+
+func (h *machinesHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if !allowMethod(w, r.Method, "GET", "HEAD") {
+		return
+	}
+	endpoints := h.cluster.ClientURLs()
+	w.Write([]byte(strings.Join(endpoints, ", ")))
+}
+
 type membersHandler struct {
 	sec                   auth.Store
 	server                etcdserver.Server

etcdserver/api/v2http/client_test.go

@@ -1220,6 +1220,56 @@ func TestWriteEvent(t *testing.T) {
 	}
 }
 
+func TestV2DMachinesEndpoint(t *testing.T) {
+	tests := []struct {
+		method string
+		wcode  int
+	}{
+		{"GET", http.StatusOK},
+		{"HEAD", http.StatusOK},
+		{"POST", http.StatusMethodNotAllowed},
+	}
+
+	m := &machinesHandler{cluster: &fakeCluster{}}
+	s := httptest.NewServer(m)
+	defer s.Close()
+
+	for _, tt := range tests {
+		req, err := http.NewRequest(tt.method, s.URL+machinesPrefix, nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if resp.StatusCode != tt.wcode {
+			t.Errorf("StatusCode = %d, expected %d", resp.StatusCode, tt.wcode)
+		}
+	}
+}
+
+func TestServeMachines(t *testing.T) {
+	cluster := &fakeCluster{
+		clientURLs: []string{"http://localhost:8080", "http://localhost:8081", "http://localhost:8082"},
+	}
+	writer := httptest.NewRecorder()
+	req, err := http.NewRequest("GET", "", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	h := &machinesHandler{cluster: cluster}
+	h.ServeHTTP(writer, req)
+	w := "http://localhost:8080, http://localhost:8081, http://localhost:8082"
+	if g := writer.Body.String(); g != w {
+		t.Errorf("body = %s, want %s", g, w)
+	}
+	if writer.Code != http.StatusOK {
+		t.Errorf("code = %d, want %d", writer.Code, http.StatusOK)
+	}
+}
+
 func TestGetID(t *testing.T) {
 	tests := []struct {
 		path string