Fix RoutingProxy hanging when there is an error

lib/node-http-proxy/routing-proxy.js

@@ -51,6 +51,18 @@ var RoutingProxy = exports.RoutingProxy = function (options) {
   this.https   = this.source.https    || options.https;
   this.enable  = options.enable;
   this.forward = options.forward;
+
+  //
+  // Listen for 'newListener' events so that we can bind 'proxyError'
+  // listeners to each HttpProxy's 'proxyError' event.
+  //
+  this.on('newListener', function (evt) {
+    if (evt === 'proxyError' || evt === 'webSocketProxyError') {
+      Object.keys(self.proxies).forEach(function (key) {
+        self.proxies[key].on(evt, this.emit.bind(this, evt));
+      });
+    }
+  });
 };
 
 
@@ -90,8 +102,12 @@ RoutingProxy.prototype.add = function (options) {
   });
 
   this.proxies[key] = new HttpProxy(options);
-  this.proxies[key].on('proxyError', this.emit.bind(this, 'proxyError'));
-  this.proxies[key].on('webSocketProxyError', this.emit.bind(this, 'webSocketProxyError'));
+  if (this.listeners('proxyError').length > 0) {
+    this.proxies[key].on('proxyError', this.emit.bind(this, 'proxyError'));
+  }
+  if (this.listeners('webSocketProxyError').length > 0) {
+    this.proxies[key].on('webSocketProxyError', this.emit.bind(this, 'webSocketProxyError'));
+  }
   this.proxies[key].on('start', this.emit.bind(this, 'start'));
   this.proxies[key].on('forward', this.emit.bind(this, 'forward'));
   this.proxies[key].on('end', this.emit.bind(this, 'end'));
@@ -188,7 +204,6 @@ RoutingProxy.prototype.proxyRequest = function (req, res, options) {
 
   if (!this.proxies[key]) {
     this.add(options);
-
   }
 
   proxy = this.proxies[key];