etcd2: watch on 0 to return ADDED always

pkg/storage/etcd/etcd_watcher.go

@@ -359,9 +359,6 @@ func (w *etcdWatcher) sendAdd(res *etcd.Response) {
 		return
 	}
 	action := watch.Added
-	if res.Node.ModifiedIndex != res.Node.CreatedIndex {
-		action = watch.Modified
-	}
 	w.emit(watch.Event{
 		Type:   action,
 		Object: obj,
@@ -454,6 +451,8 @@ func (w *etcdWatcher) sendDelete(res *etcd.Response) {
 func (w *etcdWatcher) sendResult(res *etcd.Response) {
 	switch res.Action {
 	case EtcdCreate, EtcdGet:
+		// "Get" will only happen in watch 0 case, where we explicitly want ADDED event
+		// for initial state.
 		w.sendAdd(res)
 	case EtcdSet, EtcdCAS:
 		w.sendModify(res)

pkg/storage/etcd/etcd_watcher_test.go

@@ -412,6 +412,18 @@ func TestWatchFromZeroIndex(t *testing.T) {
 	}
 	pod.ResourceVersion = ""
 
+	watching, err := h.Watch(context.TODO(), key, "0", storage.Everything)
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	// The create trigger ADDED event when watching from 0
+	event := <-watching.ResultChan()
+	watching.Stop()
+	if event.Type != watch.Added {
+		t.Errorf("Unexpected event %#v", event)
+	}
+
 	// check for concatenation on watch event with CAS
 	updateFn := func(input runtime.Object, res storage.ResponseMeta) (runtime.Object, *uint64, error) {
 		pod := input.(*api.Pod)
@@ -423,15 +435,15 @@ func TestWatchFromZeroIndex(t *testing.T) {
 		t.Fatalf("Unexpected error: %v", err)
 	}
 
-	watching, err := h.Watch(context.TODO(), key, "0", storage.Everything)
+	watching, err = h.Watch(context.TODO(), key, "0", storage.Everything)
 	if err != nil {
 		t.Fatalf("Unexpected error: %v", err)
 	}
 	defer watching.Stop()
 
-	// marked as modified b/c of concatenation
-	event := <-watching.ResultChan()
-	if event.Type != watch.Modified {
+	// because we watch from 0, first event that we receive will always be ADDED
+	event = <-watching.ResultChan()
+	if event.Type != watch.Added {
 		t.Errorf("Unexpected event %#v", event)
 	}
 
@@ -451,7 +463,7 @@ func TestWatchFromZeroIndex(t *testing.T) {
 		t.Errorf("Unexpected event %#v", event)
 	}
 
-	if e, a := pod, event.Object; !api.Semantic.DeepDerivative(e, a) {
+	if e, a := pod, event.Object; a == nil || !api.Semantic.DeepDerivative(e, a) {
 		t.Errorf("Unexpected error: expected %#v, got %#v", e, a)
 	}
 }