From 08b4de66d4ffca1a9f8ea2a32bfd449e63420497 Mon Sep 17 00:00:00 2001
From: Jeromy <why@ipfs.io>
Date: Wed, 14 Sep 2016 14:12:20 -0700
Subject: [PATCH] refactor to use multiple feeds

---
 floodsub.go | 105 ++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 82 insertions(+), 23 deletions(-)

diff --git a/floodsub.go b/floodsub.go
index 3e3b7bd0..aa147671 100644
--- a/floodsub.go
+++ b/floodsub.go
@@ -33,6 +33,9 @@ type PubSub struct {
 	// addSub is a control channel for us to add and remove subscriptions
 	addSub chan *addSub
 
+	//
+	addFeedHook chan *addFeedReq
+
 	// a notification channel for incoming streams from other peers
 	newPeers chan inet.Stream
 
@@ -40,7 +43,7 @@ type PubSub struct {
 	peerDead chan peer.ID
 
 	// The set of topics we are subscribed to
-	myTopics map[string]chan *Message
+	myTopics map[string][]*clientFeed
 
 	// topics tracks which topics each of our peers are subscribed to
 	topics map[string]map[peer.ID]struct{}
@@ -74,8 +77,9 @@ func NewFloodSub(ctx context.Context, h host.Host) *PubSub {
 		publish:      make(chan *Message),
 		newPeers:     make(chan inet.Stream),
 		peerDead:     make(chan peer.ID),
+		addFeedHook:  make(chan *addFeedReq, 32),
 		addSub:       make(chan *addSub),
-		myTopics:     make(map[string]chan *Message),
+		myTopics:     make(map[string][]*clientFeed),
 		topics:       make(map[string]map[peer.ID]struct{}),
 		peers:        make(map[peer.ID]chan *RPC),
 		seenMessages: timecache.NewTimeCache(time.Second * 30),
@@ -107,6 +111,21 @@ func (p *PubSub) processLoop(ctx context.Context) {
 
 			p.peers[pid] = messages
 
+		case req := <-p.addFeedHook:
+			feeds, ok := p.myTopics[req.topic]
+
+			var out chan *Message
+			if ok {
+				out = make(chan *Message, 32)
+				nfeed := &clientFeed{
+					out: out,
+					ctx: req.ctx,
+				}
+
+				p.myTopics[req.topic] = append(feeds, nfeed)
+			}
+
+			req.resp <- out
 		case pid := <-p.peerDead:
 			delete(p.peers, pid)
 			for _, t := range p.topics {
@@ -135,23 +154,21 @@ func (p *PubSub) handleSubscriptionChange(sub *addSub) {
 		Subscribe: &sub.sub,
 	}
 
-	ch, ok := p.myTopics[sub.topic]
+	feeds, ok := p.myTopics[sub.topic]
 	if sub.sub {
 		if ok {
-			// we don't allow multiple subs per topic at this point
-			sub.resp <- nil
 			return
 		}
 
-		resp := make(chan *Message, 16)
-		p.myTopics[sub.topic] = resp
-		sub.resp <- resp
+		p.myTopics[sub.topic] = nil
 	} else {
 		if !ok {
 			return
 		}
 
-		close(ch)
+		for _, f := range feeds {
+			close(f.out)
+		}
 		delete(p.myTopics, sub.topic)
 	}
 
@@ -163,9 +180,26 @@ func (p *PubSub) handleSubscriptionChange(sub *addSub) {
 
 func (p *PubSub) notifySubs(msg *pb.Message) {
 	for _, topic := range msg.GetTopicIDs() {
-		subch, ok := p.myTopics[topic]
-		if ok {
-			subch <- &Message{msg}
+		var cleanup bool
+		feeds := p.myTopics[topic]
+		for _, f := range feeds {
+			select {
+			case f.out <- &Message{msg}:
+			case <-f.ctx.Done():
+				close(f.out)
+				f.out = nil
+				cleanup = true
+			}
+		}
+
+		if cleanup {
+			out := make([]*clientFeed, 0, len(feeds))
+			for _, f := range feeds {
+				if f.out != nil {
+					out = append(out, f)
+				}
+			}
+			p.myTopics[topic] = out
 		}
 	}
 }
@@ -270,34 +304,59 @@ type addSub struct {
 	resp  chan chan *Message
 }
 
-func (p *PubSub) Subscribe(topic string) (<-chan *Message, error) {
-	return p.SubscribeComplicated(&pb.TopicDescriptor{
+func (p *PubSub) Subscribe(ctx context.Context, topic string) (<-chan *Message, error) {
+	err := p.AddTopicSubscription(&pb.TopicDescriptor{
 		Name: proto.String(topic),
 	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	return p.GetFeed(ctx, topic)
 }
 
-func (p *PubSub) SubscribeComplicated(td *pb.TopicDescriptor) (<-chan *Message, error) {
+func (p *PubSub) AddTopicSubscription(td *pb.TopicDescriptor) error {
 	if td.GetAuth().GetMode() != pb.TopicDescriptor_AuthOpts_NONE {
-		return nil, fmt.Errorf("Auth method not yet supported")
+		return fmt.Errorf("Auth method not yet supported")
 	}
 
 	if td.GetEnc().GetMode() != pb.TopicDescriptor_EncOpts_NONE {
-		return nil, fmt.Errorf("Encryption method not yet supported")
+		return fmt.Errorf("Encryption method not yet supported")
 	}
 
-	resp := make(chan chan *Message)
 	p.addSub <- &addSub{
 		topic: td.GetName(),
-		resp:  resp,
 		sub:   true,
 	}
 
-	outch := <-resp
-	if outch == nil {
-		return nil, fmt.Errorf("error, duplicate subscription")
+	return nil
+}
+
+type addFeedReq struct {
+	ctx   context.Context
+	topic string
+	resp  chan chan *Message
+}
+
+type clientFeed struct {
+	out chan *Message
+	ctx context.Context
+}
+
+func (p *PubSub) GetFeed(ctx context.Context, topic string) (<-chan *Message, error) {
+	out := make(chan chan *Message, 1)
+	p.addFeedHook <- &addFeedReq{
+		ctx:   ctx,
+		topic: topic,
+		resp:  out,
 	}
 
-	return outch, nil
+	resp := <-out
+	if resp == nil {
+		return nil, fmt.Errorf("not subscribed to topic %s", topic)
+	}
+	return resp, nil
 }
 
 func (p *PubSub) Unsub(topic string) {