Prepare to allow max conns per torrent to be configured

client.go

@@ -264,7 +264,7 @@ func NewClient(cfg *Config) (cl *Client, err error) {
 		}
 	}()
 	cl = &Client{
-		halfOpenLimit:     socketsPerTorrent,
+		halfOpenLimit:     defaultHalfOpenConnsPerTorrent,
 		config:            *cfg,
 		defaultStorage:    cfg.DefaultStorage,
 		dopplegangerAddrs: make(map[string]struct{}),
@@ -382,7 +382,7 @@ func (cl *Client) waitAccept() {
 	defer cl.mu.Unlock()
 	for {
 		for _, t := range cl.torrents {
-			if cl.wantConns(t) {
+			if t.wantConns() {
 				return
 			}
 		}
@@ -936,7 +936,7 @@ func (cl *Client) runHandshookConn(c *connection, t *Torrent) {
 		c.rw,
 	}
 	completedHandshakeConnectionFlags.Add(c.connectionFlags(), 1)
-	if !cl.addConnection(t, c) {
+	if !t.addConnection(c) {
 		return
 	}
 	defer t.dropConnection(c)
@@ -1337,67 +1337,10 @@ func (cl *Client) connectionLoop(t *Torrent, c *connection) error {
 	}
 }
 
-// Returns true if the connection is added.
-func (cl *Client) addConnection(t *Torrent, c *connection) bool {
-	if cl.closed.IsSet() {
-		return false
-	}
-	if !cl.wantConns(t) {
-		return false
-	}
-	for _, c0 := range t.conns {
-		if c.PeerID == c0.PeerID {
-			// Already connected to a client with that ID.
-			duplicateClientConns.Add(1)
-			return false
-		}
-	}
-	if len(t.conns) >= socketsPerTorrent {
-		c := t.worstBadConn(cl)
-		if c == nil {
-			return false
-		}
-		if cl.config.Debug && missinggo.CryHeard() {
-			log.Printf("%s: dropping connection to make room for new one:\n    %s", t, c)
-		}
-		c.Close()
-		t.deleteConnection(c)
-	}
-	if len(t.conns) >= socketsPerTorrent {
-		panic(len(t.conns))
-	}
-	t.conns = append(t.conns, c)
-	c.t = t
-	return true
-}
-
-func (cl *Client) usefulConn(t *Torrent, c *connection) bool {
-	if c.closed.IsSet() {
-		return false
-	}
-	if !t.haveInfo() {
-		return c.supportsExtension("ut_metadata")
-	}
-	if t.seeding() {
-		return c.PeerInterested
-	}
-	return t.connHasWantedPieces(c)
-}
-
-func (cl *Client) wantConns(t *Torrent) bool {
-	if !t.seeding() && !t.needData() {
-		return false
-	}
-	if len(t.conns) < socketsPerTorrent {
-		return true
-	}
-	return t.worstBadConn(cl) != nil
-}
-
 func (cl *Client) openNewConns(t *Torrent) {
 	defer t.updateWantPeersEvent()
 	for len(t.peers) != 0 {
-		if !cl.wantConns(t) {
+		if !t.wantConns() {
 			return
 		}
 		if len(t.halfOpen) >= cl.halfOpenLimit {
@@ -1431,9 +1374,7 @@ func (cl *Client) badPeerIPPort(ip net.IP, port int) bool {
 	return false
 }
 
-// Prepare a Torrent without any attachment to a Client. That means we can
+// Return a Torrent ready for insertion into a Client.
-// initialize fields all fields that don't require the Client without locking
-// it.
 func (cl *Client) newTorrent(ih metainfo.Hash) (t *Torrent) {
 	t = &Torrent{
 		cl:        cl,
@@ -1444,7 +1385,8 @@ func (cl *Client) newTorrent(ih metainfo.Hash) (t *Torrent) {
 		halfOpen:          make(map[string]struct{}),
 		pieceStateChanges: pubsub.NewPubSub(),
 
-		storageOpener: cl.defaultStorage,
+		storageOpener:       cl.defaultStorage,
+		maxEstablishedConns: defaultEstablishedConnsPerTorrent,
 	}
 	return
 }

connection.go

@@ -653,3 +653,19 @@ func (cn *connection) wroteBytes(b []byte) {
 	cn.stats.wroteBytes(b)
 	cn.t.stats.wroteBytes(b)
 }
+
+// Returns whether the connection is currently useful to us. We're seeding and
+// they want data, we don't have metainfo and they can provide it, etc.
+func (c *connection) useful() bool {
+	t := c.t
+	if c.closed.IsSet() {
+		return false
+	}
+	if !t.haveInfo() {
+		return c.supportsExtension("ut_metadata")
+	}
+	if t.seeding() {
+		return c.PeerInterested
+	}
+	return t.connHasWantedPieces(c)
+}

global.go

@@ -36,9 +36,10 @@ const (
 	// http://www.bittorrent.org/beps/bep_0005.html
 	defaultExtensionBytes = "\x00\x00\x00\x00\x00\x10\x00\x01"
 
-	socketsPerTorrent     = 80
+	defaultEstablishedConnsPerTorrent = 80
-	torrentPeersHighWater = 200
+	defaultHalfOpenConnsPerTorrent    = 80
-	torrentPeersLowWater  = 50
+	torrentPeersHighWater             = 200
+	torrentPeersLowWater              = 50
 
 	// Limit how long handshake can take. This is to reduce the lingering
 	// impact of a few bad apples. 4s loses 1% of successful handshakes that

torrent.go

@@ -61,7 +61,8 @@ type Torrent struct {
 	// The info dict. nil if we don't have it (yet).
 	info *metainfo.InfoEx
 	// Active peer connections, running message stream loops.
-	conns []*connection
+	conns               []*connection
+	maxEstablishedConns int
 	// Set of addrs to which we're attempting to connect. Connections are
 	// half-open until all handshakes are completed.
 	halfOpen map[string]struct{}
@@ -133,12 +134,8 @@ func (t *Torrent) addrActive(addr string) bool {
 	return false
 }
 
-func (t *Torrent) worstConns(cl *Client) (wcs *worstConns) {
+func (t *Torrent) worstConns() (wcs *worstConns) {
-	wcs = &worstConns{
+	wcs = &worstConns{make([]*connection, 0, len(t.conns))}
-		c:  make([]*connection, 0, len(t.conns)),
-		t:  t,
-		cl: cl,
-	}
 	for _, c := range t.conns {
 		if !c.closed.IsSet() {
 			wcs.c = append(wcs.c, c)
@@ -446,11 +443,7 @@ func (t *Torrent) writeStatus(w io.Writer, cl *Client) {
 	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{
+	sort.Sort(&worstConns{t.conns})
-		c:  t.conns,
-		t:  t,
-		cl: cl,
-	})
 	for i, c := range t.conns {
 		fmt.Fprintf(w, "%2d. ", i+1)
 		c.WriteStatus(w, t)
@@ -740,15 +733,15 @@ func (t *Torrent) extentPieces(off, _len int64) (pieces []int) {
 	return
 }
 
-func (t *Torrent) worstBadConn(cl *Client) *connection {
+func (t *Torrent) worstBadConn() *connection {
-	wcs := t.worstConns(cl)
+	wcs := t.worstConns()
 	heap.Init(wcs)
 	for wcs.Len() != 0 {
 		c := heap.Pop(wcs).(*connection)
 		if c.UnwantedChunksReceived >= 6 && c.UnwantedChunksReceived > c.UsefulChunksReceived {
 			return c
 		}
-		if wcs.Len() >= (socketsPerTorrent+1)/2 {
+		if wcs.Len() >= (t.maxEstablishedConns+1)/2 {
 			// Give connections 1 minute to prove themselves.
 			if time.Since(c.completedHandshake) > time.Minute {
 				return c
@@ -1273,3 +1266,47 @@ func (t *Torrent) addPeers(peers []Peer) {
 func (t *Torrent) Stats() TorrentStats {
 	return t.stats
 }
+
+// Returns true if the connection is added.
+func (t *Torrent) addConnection(c *connection) bool {
+	if t.cl.closed.IsSet() {
+		return false
+	}
+	if !t.wantConns() {
+		return false
+	}
+	for _, c0 := range t.conns {
+		if c.PeerID == c0.PeerID {
+			// Already connected to a client with that ID.
+			duplicateClientConns.Add(1)
+			return false
+		}
+	}
+	if len(t.conns) >= t.maxEstablishedConns {
+		c := t.worstBadConn()
+		if c == nil {
+			return false
+		}
+		if t.cl.config.Debug && missinggo.CryHeard() {
+			log.Printf("%s: dropping connection to make room for new one:\n    %s", t, c)
+		}
+		c.Close()
+		t.deleteConnection(c)
+	}
+	if len(t.conns) >= t.maxEstablishedConns {
+		panic(len(t.conns))
+	}
+	t.conns = append(t.conns, c)
+	c.t = t
+	return true
+}
+
+func (t *Torrent) wantConns() bool {
+	if !t.seeding() && !t.needData() {
+		return false
+	}
+	if len(t.conns) < t.maxEstablishedConns {
+		return true
+	}
+	return t.worstBadConn() != nil
+}

worst_conns.go

@@ -4,11 +4,9 @@ import (
 	"time"
 )
 
-// Implements heap functions such that [0] is the worst connection.
+// Implements a heap of connections by how useful they are or have been.
 type worstConns struct {
-	c  []*connection
+	c []*connection
-	t  *Torrent
-	cl *Client
 }
 
 func (wc *worstConns) Len() int      { return len(wc.c) }
@@ -44,8 +42,8 @@ func (wc worstConnsSortKey) Less(other worstConnsSortKey) bool {
 
 func (wc *worstConns) key(i int) (key worstConnsSortKey) {
 	c := wc.c[i]
-	key.useful = wc.cl.usefulConn(wc.t, c)
+	key.useful = c.useful()
-	if wc.t.seeding() {
+	if c.t.seeding() {
 		key.lastHelpful = c.lastChunkSent
 	}
 	// Intentionally consider the last time a chunk was received when seeding,