nsqd: deleting a "live" topic

nsqd/nsqd.go

@@ -292,22 +292,26 @@ func (n *NSQd) GetExistingTopic(topicName string) (*Topic, error) {
 
 // DeleteExistingTopic removes a topic only if it exists
 func (n *NSQd) DeleteExistingTopic(topicName string) error {
-	n.Lock()
+	n.RLock()
 	topic, ok := n.topicMap[topicName]
 	if !ok {
-		n.Unlock()
+		n.RUnlock()
 		return errors.New("topic does not exist")
 	}
-	delete(n.topicMap, topicName)
-	// not defered so that we can continue while the topic async closes
-	n.Unlock()
-
-	log.Printf("TOPIC(%s): deleting", topic.name)
+	n.RUnlock()
 
 	// delete empties all channels and the topic itself before closing
 	// (so that we dont leave any messages around)
+	//
+	// we do this before removing the topic from map below (with no lock)
+	// so that any incoming writes will error and not create a new topic
+	// to enforce ordering
 	topic.Delete()
 
+	n.Lock()
+	delete(n.topicMap, topicName)
+	n.Unlock()
+
 	return nil
 }
 

nsqd/topic.go

@@ -219,13 +219,10 @@ func (t *Topic) router() {
 
 // Delete empties the topic and all its channels and closes
 func (t *Topic) Delete() error {
-	err := t.exit(true)
-	// since we are explicitly deleting a topic (not just at system exit time)
-	// de-register this from the lookupd
-	go t.notifier.Notify(t)
-	return err
+	return t.exit(true)
 }
 
+// Close persists all outstanding topic data and closes all its channels
 func (t *Topic) Close() error {
 	return t.exit(false)
 }
@@ -235,7 +232,15 @@ func (t *Topic) exit(deleted bool) error {
 		return errors.New("exiting")
 	}
 
-	log.Printf("TOPIC(%s): closing", t.name)
+	if deleted {
+		log.Printf("TOPIC(%s): deleting", t.name)
+
+		// since we are explicitly deleting a topic (not just at system exit time)
+		// de-register this from the lookupd
+		go t.notifier.Notify(t)
+	} else {
+		log.Printf("TOPIC(%s): closing", t.name)
+	}
 
 	close(t.exitChan)