submatview: only return materializer from getEntry

Also rename it to readEntry now that it doesn't return the entire entry. Based on feedback
in PR review, the full entry is not used by the caller, and accessing the fields wouldn't be
safe outside the lock, so it is safer to return only the Materializer

agent/rpcclient/health/health.go

@@ -42,7 +42,6 @@ func (c *Client) ServiceNodes(
 		if err != nil {
 			return structs.IndexedCheckServiceNodes{}, cache.ResultMeta{}, err
 		}
-		// TODO: can we store non-pointer
 		return *result.Value.(*structs.IndexedCheckServiceNodes), cache.ResultMeta{Index: result.Index}, err
 	}
 

agent/submatview/materializer.go

@@ -79,7 +79,7 @@ func NewMaterializer(deps Deps) *Materializer {
 		retryWaiter: deps.Waiter,
 		updateCh:    make(chan struct{}),
 	}
-	if deps.Waiter == nil {
+	if v.retryWaiter == nil {
 		v.retryWaiter = &retry.Waiter{
 			MinFailures: 1,
 			// Start backing off with small increments (200-400ms) which will double

agent/submatview/store.go

@@ -109,7 +109,7 @@ type Request interface {
 // See agent/cache.Cache.Get for complete documentation.
 func (s *Store) Get(ctx context.Context, req Request) (Result, error) {
 	info := req.CacheInfo()
-	key, e, err := s.getEntry(req)
+	key, materializer, err := s.readEntry(req)
 	if err != nil {
 		return Result{}, err
 	}
@@ -118,7 +118,7 @@ func (s *Store) Get(ctx context.Context, req Request) (Result, error) {
 	ctx, cancel := context.WithTimeout(ctx, info.Timeout)
 	defer cancel()
 
-	result, err := e.materializer.getFromView(ctx, info.MinIndex)
+	result, err := materializer.getFromView(ctx, info.MinIndex)
 	// context.DeadlineExceeded is translated to nil to match the behaviour of
 	// agent/cache.Cache.Get.
 	if err == nil || errors.Is(err, context.DeadlineExceeded) {
@@ -139,7 +139,7 @@ func (s *Store) Notify(
 	updateCh chan<- cache.UpdateEvent,
 ) error {
 	info := req.CacheInfo()
-	key, e, err := s.getEntry(req)
+	key, materializer, err := s.readEntry(req)
 	if err != nil {
 		return err
 	}
@@ -149,7 +149,7 @@ func (s *Store) Notify(
 
 		index := info.MinIndex
 		for {
-			result, err := e.materializer.getFromView(ctx, index)
+			result, err := materializer.getFromView(ctx, index)
 			switch {
 			case ctx.Err() != nil:
 				return
@@ -182,9 +182,9 @@ func (s *Store) Notify(
 	return nil
 }
 
-// getEntry from the store, and increment the requests counter. releaseEntry
+// readEntry from the store, and increment the requests counter. releaseEntry
 // must be called when the request is finished to decrement the counter.
-func (s *Store) getEntry(req Request) (string, entry, error) {
+func (s *Store) readEntry(req Request) (string, *Materializer, error) {
 	info := req.CacheInfo()
 	key := makeEntryKey(req.Type(), info)
 
@@ -194,12 +194,12 @@ func (s *Store) getEntry(req Request) (string, entry, error) {
 	if ok {
 		e.requests++
 		s.byKey[key] = e
-		return key, e, nil
+		return key, e.materializer, nil
 	}
 
 	mat, err := req.NewMaterializer()
 	if err != nil {
-		return "", e, err
+		return "", nil, err
 	}
 
 	ctx, cancel := context.WithCancel(context.Background())
@@ -211,11 +211,11 @@ func (s *Store) getEntry(req Request) (string, entry, error) {
 		requests:     1,
 	}
 	s.byKey[key] = e
-	return key, e, nil
+	return key, e.materializer, nil
 }
 
 // releaseEntry decrements the request count and starts an expiry timer if the
-// count has reached 0. Must be called once for every call to getEntry.
+// count has reached 0. Must be called once for every call to readEntry.
 func (s *Store) releaseEntry(key string) {
 	s.lock.Lock()
 	defer s.lock.Unlock()