Prune old peers in server with lru based cache. Issue webtorrent#4

Author: yciabaud

lib/server/swarm.js

@@ -1,20 +1,25 @@
 module.exports = Swarm
 
 var debug = require('debug')('bittorrent-tracker')
+var LRU = require('lru')
 var randomIterate = require('random-iterate')
 
 // Regard this as the default implementation of an interface that you
 // need to support when overriding Server.createSwarm() and Server.getSwarm()
 function Swarm (infoHash, server) {
-  this.peers = {}
+  this.peers = new LRU({
+    max: server.peersCacheLength || 10000,
+    maxAge: server.peersCacheTtl || 900 // 900s = 15 minutes
+  })
   this.complete = 0
   this.incomplete = 0
 }
 
 Swarm.prototype.announce = function (params, cb) {
   var self = this
   var id = params.type === 'ws' ? params.peer_id : params.addr
-  var peer = self.peers[id]
+  // Mark the source peer as recently used in cache
+  var peer = self.peers.get(id)
 
   if (params.event === 'started') {
     self._onAnnounceStarted(params, peer)
@@ -51,14 +56,14 @@ Swarm.prototype._onAnnounceStarted = function (params, peer) {
   if (params.left === 0) this.complete += 1
   else this.incomplete += 1
   var id = params.type === 'ws' ? params.peer_id : params.addr
-  peer = this.peers[id] = {
+  peer = this.peers.set(id, {
     type: params.type,
     complete: params.left === 0,
     peerId: params.peer_id, // as hex
     ip: params.ip,
     port: params.port,
     socket: params.socket // only websocket
-  }
+  })
 }
 
 Swarm.prototype._onAnnounceStopped = function (params, peer) {
@@ -70,7 +75,7 @@ Swarm.prototype._onAnnounceStopped = function (params, peer) {
   if (peer.complete) this.complete -= 1
   else this.incomplete -= 1
   var id = params.type === 'ws' ? params.peer_id : params.addr
-  delete this.peers[id]
+  this.peers.remove(id)
 }
 
 Swarm.prototype._onAnnounceCompleted = function (params, peer) {
@@ -103,10 +108,11 @@ Swarm.prototype._onAnnounceUpdate = function (params, peer) {
 
 Swarm.prototype._getPeers = function (numwant, ownPeerId, isWebRTC) {
   var peers = []
-  var ite = randomIterate(Object.keys(this.peers))
+  var ite = randomIterate(Object.keys(this.peers.cache))
   var peerId
   while ((peerId = ite()) && peers.length < numwant) {
-    var peer = this.peers[peerId]
+    // Don't mark the peer as most recently used on announce
+    var peer = this.peers.peek(peerId)
     if (isWebRTC && peer.peerId === ownPeerId) continue // don't send peer to itself
     if ((isWebRTC && peer.type !== 'ws') || (!isWebRTC && peer.type === 'ws')) continue // send proper peer type
     peers.push(peer)

package.json

@@ -27,6 +27,7 @@
     "hat": "0.0.3",
     "inherits": "^2.0.1",
     "ip": "^1.0.1",
+    "lru": "^2.0.1",
     "minimist": "^1.1.1",
     "once": "^1.3.0",
     "random-iterate": "^1.0.1",

server.js

@@ -50,6 +50,9 @@ function Server (opts) {
   self._trustProxy = !!opts.trustProxy
   if (typeof opts.filter === 'function') self._filter = opts.filter
 
+  self.peersCacheLength = opts.peersCacheLength
+  self.peersCacheTtl = opts.peersCacheTtl
+
   self._listenCalled = false
   self.listening = false
   self.destroyed = false
@@ -153,7 +156,7 @@ function Server (opts) {
       if (req.method === 'GET' && (req.url === '/stats' || req.url === '/stats.json')) {
         infoHashes.forEach(function (infoHash) {
           var peers = self.torrents[infoHash].peers
-          var keys = Object.keys(peers)
+          var keys = Object.keys(peers.cache)
           if (keys.length > 0) activeTorrents++
 
           keys.forEach(function (peerId) {
@@ -165,7 +168,8 @@ function Server (opts) {
                 leecher: false
               }
             }
-            var peer = peers[peerId]
+            // Don't mark the peer as most recently used for stats
+            var peer = peers.peek(peerId)
             if (peer.ip.indexOf(':') >= 0) {
               allPeers[peerId].ipv6 = true
             } else {
@@ -489,7 +493,8 @@ Server.prototype._onWebSocketRequest = function (socket, opts, params) {
         if (!swarm) {
           return self.emit('warning', new Error('no swarm with that `info_hash`'))
         }
-        var toPeer = swarm.peers[params.to_peer_id]
+        // Mark the destination peer as recently used in cache
+        var toPeer = swarm.peers.get(params.to_peer_id)
         if (!toPeer) {
           return self.emit('warning', new Error('no peer with that `to_peer_id`'))
         }

test/server.js

@@ -52,22 +52,23 @@ function serverTest (t, serverType, serverFamily) {
         t.equal(Object.keys(server.torrents).length, 1)
         t.equal(swarm.complete, 0)
         t.equal(swarm.incomplete, 1)
-        t.equal(Object.keys(swarm.peers).length, 1)
+        t.equal(Object.keys(swarm.peers.cache).length, 1)
 
         var id = serverType === 'ws'
           ? peerId.toString('hex')
           : hostname + ':6881'
 
-        t.equal(swarm.peers[id].type, serverType)
-        t.equal(swarm.peers[id].ip, clientIp)
-        t.equal(swarm.peers[id].peerId, peerId.toString('hex'))
-        t.equal(swarm.peers[id].complete, false)
+        var peer = swarm.peers.peek(id)
+        t.equal(peer.type, serverType)
+        t.equal(peer.ip, clientIp)
+        t.equal(peer.peerId, peerId.toString('hex'))
+        t.equal(peer.complete, false)
         if (serverType === 'ws') {
-          t.equal(typeof swarm.peers[id].port, 'number')
-          t.ok(swarm.peers[id].socket)
+          t.equal(typeof peer.port, 'number')
+          t.ok(peer.socket)
         } else {
-          t.equal(swarm.peers[id].port, 6881)
-          t.notOk(swarm.peers[id].socket)
+          t.equal(peer.port, 6881)
+          t.notOk(peer.socket)
         }
 
         client1.complete()