storage: add set delete

storage/watchable_store.go

@@ -55,6 +55,22 @@ func (w watcherSetByKey) add(wa *watcher) {
 	set.add(wa)
 }
 
+func (w watcherSetByKey) delete(wa *watcher) bool {
+	k := string(wa.key)
+	if v, ok := w[k]; ok {
+		if _, ok := v[wa]; ok {
+			delete(v, wa)
+			// if there is nothing in the set,
+			// remove the set
+			if len(v) == 0 {
+				delete(w, k)
+			}
+			return true
+		}
+	}
+	return false
+}
+
 type watchable interface {
 	watch(key []byte, prefix bool, startRev int64, id WatchID, ch chan<- WatchResponse) (*watcher, cancelFunc)
 	rev() int64
@@ -203,7 +219,6 @@ func (s *watchableStore) watch(key []byte, prefix bool, startRev int64, id Watch
 		ch:     ch,
 	}
 
-	k := string(key)
 	if startRev == 0 {
 		s.synced.add(wa)
 	} else {
@@ -223,16 +238,8 @@ func (s *watchableStore) watch(key []byte, prefix bool, startRev int64, id Watch
 			return
 		}
 
-		if v, ok := s.synced[k]; ok {
-			if _, ok := v[wa]; ok {
-				delete(v, wa)
-				// if there is nothing in s.synced[k],
-				// remove the key from the synced
-				if len(v) == 0 {
-					delete(s.synced, k)
-				}
-				watcherGauge.Dec()
-			}
+		if s.synced.delete(wa) {
+			watcherGauge.Dec()
 		}
 		// If we cannot find it, it should have finished watch.
 	})