submatview: set up expiry of materializers

agent/submatview/store.go

@@ -20,7 +20,9 @@ type entry struct {
 	materializer *Materializer
 	expiry       *ttlcache.Entry
 	stop         func()
-	// TODO: add watchCount
+	// notifier is the count of active Notify goroutines. This entry will
+	// remain in the store as long as this count remains > 0.
+	notifier int
 }
 
 // TODO: start expiration loop
@@ -52,11 +54,13 @@ func (s *Store) Run(ctx context.Context) {
 			he := timer.Entry
 			s.expiryHeap.Remove(he.Index())
 
-			// TODO: expiry here
-			// if e.watchCount == 0 {}
 			e := s.byKey[he.Key()]
+
+			// Only stop the materializer if there are no active calls to Notify.
+			if e.notifier == 0 {
 				e.stop()
-			//delete(s.entries, entry.Key())
+				delete(s.byKey, he.Key())
+			}
 
 			s.lock.Unlock()
 		}
@@ -77,11 +81,11 @@ func (s *Store) Get(
 	// TODO: only the Index field of ResultMeta is relevant, return a result struct instead.
 ) (interface{}, cache.ResultMeta, error) {
 	info := req.CacheInfo()
-	key := makeEntryKey(typ, info)
-	e := s.getEntry(key, req.NewMaterializer)
-
-	// TODO: requires a lock to update the heap.
-	//s.expiryHeap.Update(e.expiry.Index(), info.Timeout + ttl)
+	e := s.getEntry(getEntryOpts{
+		typ:             typ,
+		info:            info,
+		newMaterializer: req.NewMaterializer,
+	})
 
 	// TODO: no longer any need to return cache.FetchResult from Materializer.Fetch
 	// TODO: pass context instead of Done chan, also replaces Timeout param
@@ -101,15 +105,26 @@ func (s *Store) Notify(
 	correlationID string,
 	updateCh chan<- cache.UpdateEvent,
 ) error {
-	// TODO: set entry to not expire until ctx is cancelled.
-
 	info := req.CacheInfo()
-	key := makeEntryKey(typ, info)
-	e := s.getEntry(key, req.NewMaterializer)
-
-	var index uint64
+	e := s.getEntry(getEntryOpts{
+		typ:             typ,
+		info:            info,
+		newMaterializer: req.NewMaterializer,
+		notifier:        true,
+	})
 
 	go func() {
+		index := info.MinIndex
+
+		// TODO: better way to handle this?
+		defer func() {
+			s.lock.Lock()
+			e.notifier--
+			s.byKey[e.expiry.Key()] = e
+			s.expiryHeap.Update(e.expiry.Index(), idleTTL)
+			s.lock.Unlock()
+		}()
+
 		for {
 			result, err := e.materializer.Fetch(ctx.Done(), cache.FetchOptions{MinIndex: index})
 			switch {
@@ -140,28 +155,33 @@ func (s *Store) Notify(
 	return nil
 }
 
-func (s *Store) getEntry(key string, newMat func() *Materializer) entry {
-	s.lock.RLock()
-	e, ok := s.byKey[key]
-	s.lock.RUnlock()
-	if ok {
-		return e
-	}
+func (s *Store) getEntry(opts getEntryOpts) entry {
+	info := opts.info
+	key := makeEntryKey(opts.typ, info)
 
 	s.lock.Lock()
 	defer s.lock.Unlock()
-	// Check again after acquiring the write lock, in case we raced to create the entry.
-	e, ok = s.byKey[key]
+	e, ok := s.byKey[key]
 	if ok {
+		s.expiryHeap.Update(e.expiry.Index(), info.Timeout+idleTTL)
+		if opts.notifier {
+			e.notifier++
+		}
 		return e
 	}
 
-	e = entry{materializer: newMat()}
-
 	ctx, cancel := context.WithCancel(context.Background())
-	e.stop = cancel
-	go e.materializer.Run(ctx)
+	mat := opts.newMaterializer()
+	go mat.Run(ctx)
 
+	e = entry{
+		materializer: mat,
+		stop:         cancel,
+		expiry:       s.expiryHeap.Add(key, info.Timeout+idleTTL),
+	}
+	if opts.notifier {
+		e.notifier++
+	}
 	s.byKey[key] = e
 	return e
 }
@@ -175,3 +195,10 @@ type Request interface {
 	cache.Request
 	NewMaterializer() *Materializer
 }
+
+type getEntryOpts struct {
+	typ             string
+	info            cache.RequestInfo
+	newMaterializer func() *Materializer
+	notifier        bool
+}