gistfile1.txt

diff --git pkg/server/sotw/v3/server.go pkg/server/sotw/v3/server.go
index b217b6cf..19d90612 100644
--- pkg/server/sotw/v3/server.go
+++ pkg/server/sotw/v3/server.go
@@ -124,14 +124,6 @@ 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
@@ -206,25 +198,31 @@ func (s *server) process(str stream.Stream, reqCh <-chan *discovery.DiscoveryReq
 				if w.nonce == "" || w.nonce == nonce {
 					w.Cancel()
 
-					open(w, req, responder)
+					watches.addWatch(typeURL, &watch{
+						cancel:       s.cache.CreateWatch(req, streamState, responder),
+						nonce:        w.nonce,
+						responseChan: 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)
-
-				open(w, req, responder)
+				watches.addWatch(typeURL, &watch{
+					cancel:       s.cache.CreateWatch(req, streamState, responder),
+					responseChan: responder,
+				})
 			}
+
+			// Recompute the dynamic select cases.
+			watches.RecomputeWatches(s.ctx, reqCh)
 		default:
 			// Channel n -> these are the dynamic list of responders that correspond to the stream request typeURL
 			if !ok {
-				return status.Errorf(codes.Unavailable, "resource watch failed")
+				// Receiver channel was closed. TODO(jpeach) probably cancel the watch or something?
+				return status.Errorf(codes.Unavailable, "resource watch %d failed", index)
 			}
 
 			res := value.Interface().(cache.Response)
-			nonce, err := send(value.Interface().(cache.Response))
+			nonce, err := send(res)
 			if err != nil {
 				return err
 			}
diff --git pkg/server/sotw/v3/watches.go pkg/server/sotw/v3/watches.go
index 2c40022e..4d7c7fc8 100644
--- pkg/server/sotw/v3/watches.go
+++ pkg/server/sotw/v3/watches.go
@@ -6,6 +6,7 @@ import (
 
 	discovery "github.com/envoyproxy/go-control-plane/envoy/service/discovery/v3"
 	"github.com/envoyproxy/go-control-plane/pkg/cache/types"
+	"github.com/envoyproxy/go-control-plane/pkg/cache/v3"
 )
 
 // watches for all xDS resource types
@@ -31,38 +32,40 @@ func (w *watches) Cancel() {
 	}
 }
 
+func (w *watches) addWatch(typeURL string, watch *watch) {
+	w.responders[typeURL] = watch
+}
+
 // recomputeWatches rebuilds the known list of dynamic channels if needed
 func (w *watches) RecomputeWatches(ctx context.Context, req <-chan *discovery.DiscoveryRequest) {
-	cases := []reflect.SelectCase{
-		{
+	w.cases = w.cases[:0] // Clear while retaining capacity.
+
+	w.cases = append(w.cases,
+		reflect.SelectCase{
 			Dir:  reflect.SelectRecv,
 			Chan: reflect.ValueOf(ctx.Done()),
 		},
-		{
+		reflect.SelectCase{
 			Dir:  reflect.SelectRecv,
 			Chan: reflect.ValueOf(req),
 		},
-	}
+	)
 
-	index := len(cases)
-	for _, watch := range w.responders {
-		cases = append(cases, w.cases[watch.index])
-		watch.index = index
-		index++
+	for _, r := range w.responders {
+		w.cases = append(w.cases,
+			reflect.SelectCase{
+				Dir:  reflect.SelectRecv,
+				Chan: reflect.ValueOf(r.responseChan),
+			},
+		)
 	}
-
-	w.cases = cases
 }
 
 // watch contains the necessary modifiables for receiving resource responses
 type watch struct {
-	cancel func()
-	nonce  string
-
-	// Index is used to track the location of this channel in watches. This allows us
-	// to update the channel used at this slot without recomputing the entire list of select
-	// statements.
-	index int
+	cancel       func()
+	nonce        string
+	responseChan chan cache.Response
 }
 
 // Cancel calls terminate and cancel