handle creation of new watche more explicitly

Signed-off-by: Alec Holmes <[email protected]>

pkg/server/sotw/v3/server.go

@@ -124,6 +124,14 @@ func (s *server) process(str stream.Stream, reqCh <-chan *discovery.DiscoveryReq
 		return out.Nonce, str.Send(out)
 	}
 
+	open := func(w *watch, req *discovery.DiscoveryRequest, responder chan cache.Response) {
+		w.cancel = s.cache.CreateWatch(req, streamState, responder)
+		watches.cases[w.index] = reflect.SelectCase{
+			Dir:  reflect.SelectRecv,
+			Chan: reflect.ValueOf(responder),
+		}
+	}
+
 	if s.callbacks != nil {
 		if err := s.callbacks.OnStreamOpen(str.Context(), streamID, defaultTypeURL); err != nil {
 			return err
@@ -191,25 +199,23 @@ func (s *server) process(str stream.Stream, reqCh <-chan *discovery.DiscoveryReq
 			}
 
 			typeURL := req.GetTypeUrl()
-
-			w, ok := watches.responders[typeURL]
-			if !ok {
+			responder := make(chan cache.Response, 1)
+			if w, ok := watches.responders[typeURL]; ok {
+				// We've found a pre-existing watch, lets check and update if needed.
+				// If these requirements aren't satisfied, leave an open watch.
+				if w.nonce == "" || w.nonce == nonce {
+					w.Cancel()
+
+					open(w, req, responder)
+				}
+			} else {
+				// No pre-existing watch exists, let's create one.
+				// We need to precompute the watches first then open a watch in the cache.
 				watches.responders[typeURL] = &watch{}
-
 				w = watches.responders[typeURL]
 				watches.RecomputeWatches(s.ctx, reqCh)
-			}
-			if w.nonce == "" || w.nonce == nonce {
-				if w.cancel != nil {
-					w.cancel()
-				}
 
-				responder := make(chan cache.Response, 1)
-				w.cancel = s.cache.CreateWatch(req, streamState, responder)
-				watches.cases[w.index] = reflect.SelectCase{
-					Dir:  reflect.SelectRecv,
-					Chan: reflect.ValueOf(responder),
-				}
+				open(w, req, responder)
 			}
 		default:
 			// Channel n -> these are the dynamic list of responders that correspond to the stream request typeURL