Merge pull request #1050 from ploxiln/create_topic_paused

nsqd: create Topic paused

nsqd/nsqd.go

@@ -504,19 +504,15 @@ func (n *NSQD) GetTopic(topicName string) *Topic {
 	t = NewTopic(topicName, &context{n}, deleteCallback)
 	n.topicMap[topicName] = t
 
-	// if we're creating a new topic in this process while we're loading from metadata, the topic may already
-	// have message data persisted on disk. To ensure that all channels are created before message flow
-	// begins, we pause the topic.
-	if atomic.LoadInt32(&n.isLoading) == 1 {
-		t.Pause()
-	}
+	n.Unlock()
 
 	n.logf(LOG_INFO, "TOPIC(%s): created", t.name)
+	// topic is created paused, only un-pause after adding channels
 
-	// release our global nsqd lock, and switch to a more granular topic lock while we init our
-	// channels from lookupd. This blocks concurrent PutMessages to this topic.
-	t.Lock()
-	n.Unlock()
+	// if loading metadata at startup, no lookupd connections yet, and topic un-paused elsewhere
+	if atomic.LoadInt32(&n.isLoading) == 1 {
+		return t
+	}
 
 	// if using lookupd, make a blocking call to get the topics, and immediately create them.
 	// this makes sure that any message received is buffered to the right channels
@@ -528,28 +524,16 @@ func (n *NSQD) GetTopic(topicName string) *Topic {
 		}
 		for _, channelName := range channelNames {
 			if strings.HasSuffix(channelName, "#ephemeral") {
-				// we don't want to pre-create ephemeral channels
-				// because there isn't a client connected
-				continue
+				continue // do not create ephemeral channel with no consumer client
 			}
-			t.getOrCreateChannel(channelName)
+			t.GetChannel(channelName)
 		}
 	} else if len(n.getOpts().NSQLookupdTCPAddresses) > 0 {
 		n.logf(LOG_ERROR, "no available nsqlookupd to query for channels to pre-create for topic %s", t.name)
 	}
 
-	t.Unlock()
-
-	// NOTE: I would prefer for this to only happen in topic.GetChannel() but we're special
-	// casing the code above so that we can control the locks such that it is impossible
-	// for a message to be written to a (new) topic while we're looking up channels
-	// from lookupd...
-	//
-	// update messagePump state
-	select {
-	case t.channelUpdateChan <- 1:
-	case <-t.exitChan:
-	}
+	// now that all channels are added we can un-pause topic
+	t.UnPause()
 	return t
 }
 

nsqd/topic.go

@@ -49,6 +49,7 @@ func NewTopic(topicName string, ctx *context, deleteCallback func(*Topic)) *Topi
 		exitChan:          make(chan int),
 		channelUpdateChan: make(chan int),
 		ctx:               ctx,
+		paused:            1,
 		pauseChan:         make(chan bool),
 		deleteCallback:    deleteCallback,
 		idFactory:         NewGUIDFactory(ctx.nsqd.getOpts().ID),
@@ -225,17 +226,7 @@ func (t *Topic) messagePump() {
 	var chans []*Channel
 	var memoryMsgChan chan *Message
 	var backendChan chan []byte
-
-	t.RLock()
-	for _, c := range t.channelMap {
-		chans = append(chans, c)
-	}
-	t.RUnlock()
-
-	if len(chans) > 0 {
-		memoryMsgChan = t.memoryMsgChan
-		backendChan = t.backend.ReadChan()
-	}
+	// always starts with no channels, channels added async with notification
 
 	for {
 		select {