etcdhttp: support member/leader endpoint

etcdserver/etcdhttp/client.go

@@ -159,14 +159,26 @@ func (h *membersHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 	switch r.Method {
 	case "GET":
-		if trimPrefix(r.URL.Path, membersPrefix) != "" {
+		switch trimPrefix(r.URL.Path, membersPrefix) {
+		case "":
+			mc := newMemberCollection(h.clusterInfo.Members())
+			w.Header().Set("Content-Type", "application/json")
+			if err := json.NewEncoder(w).Encode(mc); err != nil {
+				log.Printf("etcdhttp: %v", err)
+			}
+		case "leader":
+			id := h.server.Leader()
+			if id == 0 {
+				writeError(w, httptypes.NewHTTPError(http.StatusServiceUnavailable, "During election"))
+				return
+			}
+			m := newMember(h.clusterInfo.Member(id))
+			w.Header().Set("Content-Type", "application/json")
+			if err := json.NewEncoder(w).Encode(m); err != nil {
+				log.Printf("etcdhttp: %v", err)
+			}
+		default:
 			writeError(w, httptypes.NewHTTPError(http.StatusNotFound, "Not found"))
-			return
-		}
-		mc := newMemberCollection(h.clusterInfo.Members())
-		w.Header().Set("Content-Type", "application/json")
-		if err := json.NewEncoder(w).Encode(mc); err != nil {
-			log.Printf("etcdhttp: %v", err)
 		}
 	case "POST":
 		req := httptypes.MemberCreateRequest{}

etcdserver/etcdhttp/client_test.go

@@ -92,9 +92,10 @@ type serverRecorder struct {
 	actions []action
 }
 
-func (s *serverRecorder) Start()       {}
-func (s *serverRecorder) Stop()        {}
-func (s *serverRecorder) ID() types.ID { return types.ID(1) }
+func (s *serverRecorder) Start()           {}
+func (s *serverRecorder) Stop()            {}
+func (s *serverRecorder) Leader() types.ID { return types.ID(1) }
+func (s *serverRecorder) ID() types.ID     { return types.ID(1) }
 func (s *serverRecorder) Do(_ context.Context, r etcdserverpb.Request) (etcdserver.Response, error) {
 	s.actions = append(s.actions, action{name: "Do", params: []interface{}{r}})
 	return etcdserver.Response{}, nil
@@ -139,9 +140,10 @@ type resServer struct {
 	res etcdserver.Response
 }
 
-func (rs *resServer) Start()       {}
-func (rs *resServer) Stop()        {}
-func (rs *resServer) ID() types.ID { return types.ID(1) }
+func (rs *resServer) Start()           {}
+func (rs *resServer) Stop()            {}
+func (rs *resServer) ID() types.ID     { return types.ID(1) }
+func (rs *resServer) Leader() types.ID { return types.ID(1) }
 func (rs *resServer) Do(_ context.Context, _ etcdserverpb.Request) (etcdserver.Response, error) {
 	return rs.res, nil
 }
@@ -604,6 +606,57 @@ func TestServeMembers(t *testing.T) {
 	}
 }
 
+// TODO: consolidate **ALL** fake server implementations and add no leader test case.
+func TestServeLeader(t *testing.T) {
+	memb1 := etcdserver.Member{ID: 1, Attributes: etcdserver.Attributes{ClientURLs: []string{"http://localhost:8080"}}}
+	memb2 := etcdserver.Member{ID: 2, Attributes: etcdserver.Attributes{ClientURLs: []string{"http://localhost:8081"}}}
+	cluster := &fakeCluster{
+		id:      1,
+		members: map[uint64]*etcdserver.Member{1: &memb1, 2: &memb2},
+	}
+	h := &membersHandler{
+		server:      &serverRecorder{},
+		clock:       clockwork.NewFakeClock(),
+		clusterInfo: cluster,
+	}
+
+	wmc := string(`{"id":"1","name":"","peerURLs":[],"clientURLs":["http://localhost:8080"]}`)
+
+	tests := []struct {
+		path  string
+		wcode int
+		wct   string
+		wbody string
+	}{
+		{membersPrefix + "leader", http.StatusOK, "application/json", wmc + "\n"},
+		// TODO: add no leader case
+	}
+
+	for i, tt := range tests {
+		req, err := http.NewRequest("GET", mustNewURL(t, tt.path).String(), nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		rw := httptest.NewRecorder()
+		h.ServeHTTP(rw, req)
+
+		if rw.Code != tt.wcode {
+			t.Errorf("#%d: code=%d, want %d", i, rw.Code, tt.wcode)
+		}
+		if gct := rw.Header().Get("Content-Type"); gct != tt.wct {
+			t.Errorf("#%d: content-type = %s, want %s", i, gct, tt.wct)
+		}
+		gcid := rw.Header().Get("X-Etcd-Cluster-ID")
+		wcid := cluster.ID().String()
+		if gcid != wcid {
+			t.Errorf("#%d: cid = %s, want %s", i, gcid, wcid)
+		}
+		if rw.Body.String() != tt.wbody {
+			t.Errorf("#%d: body = %q, want %q", i, rw.Body.String(), tt.wbody)
+		}
+	}
+}
+
 func TestServeMembersCreate(t *testing.T) {
 	u := mustNewURL(t, membersPrefix)
 	b := []byte(`{"peerURLs":["http://127.0.0.1:1"]}`)

etcdserver/etcdhttp/http_test.go

@@ -65,9 +65,10 @@ type errServer struct {
 	err error
 }
 
-func (fs *errServer) Start()       {}
-func (fs *errServer) Stop()        {}
-func (fs *errServer) ID() types.ID { return types.ID(1) }
+func (fs *errServer) Start()           {}
+func (fs *errServer) Stop()            {}
+func (fs *errServer) ID() types.ID     { return types.ID(1) }
+func (fs *errServer) Leader() types.ID { return types.ID(1) }
 func (fs *errServer) Do(ctx context.Context, r etcdserverpb.Request) (etcdserver.Response, error) {
 	return etcdserver.Response{}, fs.err
 }

etcdserver/server.go

@@ -93,6 +93,8 @@ type Server interface {
 	Stop()
 	// ID returns the ID of the Server.
 	ID() types.ID
+	// Leader returns the ID of the leader Server.
+	Leader() types.ID
 	// Do takes a request and attempts to fulfill it, returning a Response.
 	Do(ctx context.Context, r pb.Request) (Response, error)
 	// Process takes a raft message and applies it to the server's raft state
@@ -579,6 +581,8 @@ func (s *EtcdServer) Term() uint64 { return atomic.LoadUint64(&s.raftTerm) }
 // Index, Term, Lead, Committed, Applied, LastIndex, etc.
 func (s *EtcdServer) Lead() uint64 { return atomic.LoadUint64(&s.raftLead) }
 
+func (s *EtcdServer) Leader() types.ID { return types.ID(s.Lead()) }
+
 // configure sends a configuration change through consensus and
 // then waits for it to be applied to the server. It
 // will block until the change is performed or there is an error.