Move half-open tracking into per-torrent

client.go

@@ -127,8 +127,8 @@ type Client struct {
 	event sync.Cond
 	quit  chan struct{}
 
-	halfOpen    int
 	handshaking int
+
 	torrents map[InfoHash]*torrent
 
 	dataWaits map[*torrent][]dataWait
@@ -149,7 +149,6 @@ func (cl *Client) WriteStatus(w io.Writer) {
 	defer cl.mu.Unlock()
 	fmt.Fprintf(w, "Listening on %s\n", cl.ListenAddr())
 	fmt.Fprintf(w, "Peer ID: %q\n", cl.peerID)
-	fmt.Fprintf(w, "Half open outgoing connections: %d\n", cl.halfOpen)
 	fmt.Fprintf(w, "Handshaking: %d\n", cl.handshaking)
 	if cl.dHT != nil {
 		fmt.Fprintf(w, "DHT nodes: %d\n", cl.dHT.NumNodes())
@@ -373,18 +372,12 @@ func (me *Client) initiateConn(peer Peer, t *torrent) {
 	if peer.Id == me.peerID {
 		return
 	}
-	addr := &net.TCPAddr{
-		IP:   peer.IP,
-		Port: peer.Port,
-	}
-	// Don't connect to the same address twice for the same torrent.
-	for _, c := range torrent.Conns {
-		if c.Socket.RemoteAddr().String() == addr.String() {
+	addr := net.JoinHostPort(peer.IP.String(), fmt.Sprintf("%d", peer.Port))
+	if t.addrActive(addr) {
 		duplicateConnsAvoided.Add(1)
 		return
 	}
-	}
-	me.halfOpen++
+	t.HalfOpen[addr] = struct{}{}
 	go func() {
 		// Binding to the listener address and dialing via net.Dialer gives
 		// "address in use" error. It seems it's not possible to dial out from
@@ -401,10 +394,10 @@ func (me *Client) initiateConn(peer Peer, t *torrent) {
 		go func() {
 			me.mu.Lock()
 			defer me.mu.Unlock()
-			if me.halfOpen == 0 {
-				panic("assert")
+			if _, ok := t.HalfOpen[addr]; !ok {
+				panic("invariant broken")
 			}
-			me.halfOpen--
+			delete(t.HalfOpen, addr)
 			me.openNewConns()
 		}()
 
@@ -1078,10 +1071,10 @@ func (me *Client) openNewConns() {
 		default:
 		}
 		for len(t.Peers) != 0 {
-			if me.halfOpen >= me.halfOpenLimit {
+			if len(t.HalfOpen) >= me.halfOpenLimit {
 				return
 			}
-			if me.halfOpen+me.handshaking+len(t.Conns) >= socketsPerTorrent {
+			if len(t.HalfOpen)+me.handshaking+len(t.Conns) >= socketsPerTorrent {
 				break
 			}
 			var (
@@ -1152,7 +1145,7 @@ func (cl *Client) setMetaData(t *torrent, md metainfo.Info, bytes []byte) (err e
 // Prepare a Torrent without any attachment to a Client. That means we can
 // initialize fields all fields that don't require the Client without locking
 // it.
-func newTorrent(ih InfoHash, announceList [][]string) (t *torrent, err error) {
+func newTorrent(ih InfoHash, announceList [][]string, halfOpenLimit int) (t *torrent, err error) {
 	t = &torrent{
 		InfoHash: ih,
 		Peers:    make(map[peersKey]Peer, 2000),
@@ -1161,6 +1154,8 @@ func newTorrent(ih InfoHash, announceList [][]string) (t *torrent, err error) {
 		ceasingNetworking: make(chan struct{}),
 
 		gotMetainfo: make(chan *metainfo.MetaInfo, 1),
+
+		HalfOpen: make(map[string]struct{}, halfOpenLimit),
 	}
 	t.GotMetainfo = t.gotMetainfo
 	t.Trackers = make([][]tracker.Client, len(announceList))
@@ -1191,7 +1186,7 @@ func (cl *Client) AddMagnet(uri string) (t *torrent, err error) {
 	if err != nil {
 		return
 	}
-	t, err = newTorrent(m.InfoHash, [][]string{m.Trackers})
+	t, err = newTorrent(m.InfoHash, [][]string{m.Trackers}, cl.halfOpenLimit)
 	if err != nil {
 		return
 	}
@@ -1245,7 +1240,7 @@ func (me *Client) addTorrent(t *torrent) (err error) {
 func (me *Client) AddTorrent(metaInfo *metainfo.MetaInfo) (err error) {
 	var ih InfoHash
 	CopyExact(&ih, metaInfo.Info.Hash)
-	t, err := newTorrent(ih, metaInfo.AnnounceList)
+	t, err := newTorrent(ih, metaInfo.AnnounceList, me.halfOpenLimit)
 	if err != nil {
 		return
 	}

client_test.go

@@ -41,7 +41,7 @@ func TestTorrentInitialState(t *testing.T) {
 	tor, err := newTorrent(func() (ih InfoHash) {
 		util.CopyExact(ih[:], mi.Info.Hash)
 		return
-	}(), nil)
+	}(), nil, 0)
 	if err != nil {
 		t.Fatal(err)
 	}

torrent.go

@@ -59,8 +59,15 @@ type torrent struct {
 	Data     mmap_span.MMapSpan
 
 	Info *metainfo.Info
+	// Active peer connections.
 	Conns []*connection
+	// Set of addrs to which we're attempting to connect.
+	HalfOpen map[string]struct{}
+	// Reserve of peers to connect to. A peer can be both here and in the
+	// active connections if were told about the peer after connecting with
+	// them. That encourages us to reconnect to peers that are well known.
 	Peers map[peersKey]Peer
+
 	// BEP 12 Multitracker Metadata Extension. The tracker.Client instances
 	// mirror their respective URLs from the announce-list key.
 	Trackers     [][]tracker.Client
@@ -72,6 +79,18 @@ type torrent struct {
 	GotMetainfo <-chan *metainfo.MetaInfo
 }
 
+func (t *torrent) addrActive(addr string) bool {
+	if _, ok := t.HalfOpen[addr]; ok {
+		return true
+	}
+	for _, c := range t.Conns {
+		if c.Socket.RemoteAddr().String() == addr {
+			return true
+		}
+	}
+	return false
+}
+
 func (t *torrent) worstConnsHeap() (wcs *worstConns) {
 	wcs = &worstConns{
 		c: append([]*connection{}, t.Conns...),
@@ -301,6 +320,7 @@ func (t *torrent) WriteStatus(w io.Writer) {
 	}
 	fmt.Fprintln(w)
 	fmt.Fprintf(w, "Pending peers: %d\n", len(t.Peers))
+	fmt.Fprintf(w, "Half open: %d\n", len(t.HalfOpen))
 	fmt.Fprintf(w, "Active peers: %d\n", len(t.Conns))
 	sort.Sort(&worstConns{
 		c: t.Conns,

torrent_test.go

@@ -44,7 +44,7 @@ func TestTorrentRequest(t *testing.T) {
 }
 
 func TestTorrentDoubleClose(t *testing.T) {
-	tt, err := newTorrent(InfoHash{}, nil)
+	tt, err := newTorrent(InfoHash{}, nil, 0)
 	if err != nil {
 		t.Fatal(err)
 	}