discoverd: fixes expected behavior of client.Service() as described in …

…#4

discover/backend_etcd.go

@@ -39,6 +39,7 @@ func (b *EtcdBackend) Subscribe(name string) (UpdateStream, error) {
 				stream.ch <- update
 			}
 		}
+		stream.ch <- &ServiceUpdate{}
 		for u := range watch {
 			if update := b.responseToUpdate(u); update != nil {
 				stream.ch <- update

discover/backend_etcd_test.go

@@ -69,8 +69,11 @@ func TestEtcdBackend_Subscribe(t *testing.T) {
 	backend.Register("test_subscribe", "10.0.0.4", nil)
 	defer backend.Unregister("test_subscribe", "10.0.0.4")
 
-	for i := 0; i < 4; i++ {
+	for i := 0; i < 5; i++ {
 		update := <-updates.Chan()
+		if update.Addr == "" && update.Name == "" {
+			continue // skip the update that signals "up to current" event
+		}
 		if update.Online != true {
 			t.Fatal("Unexpected offline service update: ", update, i)
 		}

discover/client.go

@@ -29,9 +29,18 @@ type ServiceSet struct {
 	lisMutex  sync.Mutex
 }
 
-func (s *ServiceSet) Bind(updates chan *ServiceUpdate) {
+func (s *ServiceSet) bind(updates chan *ServiceUpdate) chan bool {
+	// current is an event when enough service updates have been
+	// received to bring us to "current" state (when subscribed)
+	current := make(chan bool)
 	go func() {
+		isCurrent := false
 		for update := range updates {
+			if update.Addr == "" && update.Name == "" && !isCurrent {
+				current <- true
+				isCurrent = true
+				continue
+			}
 			// TODO: apply filters
 			s.serMutex.Lock()
 			if _, exists := s.services[update.Addr]; !exists {
@@ -55,6 +64,7 @@ func (s *ServiceSet) Bind(updates chan *ServiceUpdate) {
 			}
 		}
 	}()
+	return current
 }
 
 func (s *ServiceSet) Online() []*Service {
@@ -149,7 +159,7 @@ func (c *DiscoverClient) Services(name string) *ServiceSet {
 		filters:   make(map[string]string),
 		listeners: make(map[chan *ServiceUpdate]struct{}),
 	}
-	set.Bind(updates)
+	<-set.bind(updates)
 	return set
 }
 

discover/client_test.go

@@ -27,10 +27,6 @@ func TestClient(t *testing.T) {
 		t.Fatal("Registering service failed", err.Error())
 	}
 	set := client.Services(serviceName)
-	ch := make(chan *ServiceUpdate)
-	set.Subscribe(ch)
-	<-ch
-	<-ch
 	if len(set.Online()) < 2 {
 		t.Fatal("Registered services not online")
 	}