client: socketPool should not be shared across clients

Caught this issue because of the new eviction tests. Essentially, this
change moves the socketPool into the client instance instead of a
reused variable at the module level.

When a client sends stop (or is evicted) the server will close the
websocket connection if that client is not in any other swarms (based
on peerId). However, if we are using a single socket for multiple
clients (as was the case before this commit), then other clients will
have their sockets unintentionally closed by the server.

Author: feross

client.js

@@ -69,6 +69,11 @@ function Client (opts) {
   // See: https://github.com/feross/webtorrent-hybrid/issues/46
   self._wrtc = typeof opts.wrtc === 'function' ? opts.wrtc() : opts.wrtc
 
+  // Use a socket pool, so WebSocket tracker clients share WebSocket objects for
+  // the same server. In practice, WebSockets are pretty slow to establish, so this
+  // gives a nice performance boost, and saves browser resources.
+  self._socketPool = {}
+
   var announce = typeof opts.announce === 'string'
     ? [ opts.announce ]
     : opts.announce == null ? [] : opts.announce

lib/client/websocket-tracker.js

@@ -10,11 +10,6 @@ var Socket = require('simple-websocket')
 var common = require('../common')
 var Tracker = require('./tracker')
 
-// Use a socket pool, so tracker clients share WebSocket objects for the same server.
-// In practice, WebSockets are pretty slow to establish, so this gives a nice performance
-// boost, and saves browser resources.
-var socketPool = {}
-
 var RECONNECT_MINIMUM = 15 * 1000
 var RECONNECT_MAXIMUM = 30 * 60 * 1000
 var RECONNECT_VARIANCE = 30 * 1000
@@ -129,15 +124,15 @@ WebSocketTracker.prototype.destroy = function (cb) {
   self._onSocketDataBound = null
   self._onSocketCloseBound = null
 
-  if (socketPool[self.announceUrl]) {
-    socketPool[self.announceUrl].consumers -= 1
+  if (self.client._socketPool[self.announceUrl]) {
+    self.client._socketPool[self.announceUrl].consumers -= 1
   }
 
   // Other instances are using the socket, so there's nothing left to do here
-  if (socketPool[self.announceUrl].consumers > 0) return cb()
+  if (self.client._socketPool[self.announceUrl].consumers > 0) return cb()
 
-  var socket = socketPool[self.announceUrl]
-  delete socketPool[self.announceUrl]
+  var socket = self.client._socketPool[self.announceUrl]
+  delete self.client._socketPool[self.announceUrl]
   socket.on('error', noop) // ignore all future errors
   socket.once('close', cb)
 
@@ -182,11 +177,11 @@ WebSocketTracker.prototype._openSocket = function () {
     self._onSocketClose()
   }
 
-  self.socket = socketPool[self.announceUrl]
+  self.socket = self.client._socketPool[self.announceUrl]
   if (self.socket) {
-    socketPool[self.announceUrl].consumers += 1
+    self.client._socketPool[self.announceUrl].consumers += 1
   } else {
-    self.socket = socketPool[self.announceUrl] = new Socket(self.announceUrl)
+    self.socket = self.client._socketPool[self.announceUrl] = new Socket(self.announceUrl)
     self.socket.consumers = 1
     self.socket.once('connect', self._onSocketConnectBound)
   }