Close websockets when peers are evicted from LRU cache

Possibly fixes: webtorrent#196

Close websockets when peers are evicted from LRU cache, otherwise it's
possible for a peer object to be evicted from the LRU cache without the
socket being cleaned up. That will leak memory until the websocket is
closed by the remote client. It also messes up the stats.

Author: feross

lib/server/swarm.js

@@ -7,12 +7,24 @@ 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.complete = 0
+  this.incomplete = 0
   this.peers = new LRU({
     max: server.peersCacheLength || 1000,
     maxAge: server.peersCacheTtl || 20 * 60 * 1000 // 20 minutes
   })
-  this.complete = 0
-  this.incomplete = 0
+
+  // When a peer is evicted from the LRU cache, if it's a websocket peer,
+  // close the websocket.
+  this.peers.on('evict', function (data) {
+    var peer = data.value
+    if (peer.socket) {
+      try {
+        peer.socket.close()
+        peer.socket = null
+      } catch (err) {}
+    }
+  })
 }
 
 Swarm.prototype.announce = function (params, cb) {