Not working on http.ServerResponse closing since Node 0.6.7

[rstuven]

Due to a change in Node http module, there is a loss of scope in a wrapped callback, resulting in an error.

[rstuven]

A workaround is to monkey patch Node:

         var ServerResponse = require('http').ServerResponse;
         ServerResponse.prototype.assignSocket = function(socket) {
           var that = socket._httpMessage = this;
           this.onServerResponseClose = function onServerResponseClose() {
               that.emit('close');
           };
           socket.on('close', this.onServerResponseClose);
           this.socket = socket;
           this.connection = socket;
           this._flush();
         };
         ServerResponse.prototype.detachSocket = function(socket) {
           socket.removeListener('close', this.onServerResponseClose);
           socket._httpMessage = null;
           this.socket = this.connection = null;
         };

[Adam Crabtree (CrabDude's alias)]

I manage the trycatch module (async try/catch), and I use Tom's long-stack-traces technique. I came across this issue as well, but it wasn't an option to turn off in production b/c we use trycatch for stability.

It turns out the issue is related to how long-stack-traces' (LST) shims functions, EventEmitter specifically. If you're not familiar with LST's internals, what it basically does is the following:

1. Shim node.js' (JavaScript's) async functions
2. In the shims, shim/wrap callbacks before passing them to original function so we can wrap a try/catch around the invocation of the callback

Unfortunately this breaks EventEmitter.removeListener b/c removeListener uses a === to pop event handlers from the stack, and the functions you pass removeListener are not the same that were passed to the original addListener / on and are thus not removed. This creates both a memory leak, and situations like this where node.js internals expect a specific remove to resolve before calling emit.

That's why this patch works, b/c you're effectively preventing the _httpMessage from being GC'd, but the problem is you're emitting a close event that should never fire. At any rate, for you guys to resolve this in LST, you'd need to implement something similar to what I'm doing in trycatch:

https://github.com/CrabDude/trycatch/blob/master/lib/hook.js#L40-60

// Wrap EventEmitters
var EventEmitter = require('events').EventEmitter
var onEvent = EventEmitter.prototype.on
EventEmitter.prototype.on = EventEmitter.prototype.addListener = function (type, callback) {
  var newCallback

  callback._wrappedCallback = callback._wrappedCallback || []
  newCallback = wrap(callback, 'EventEmitter.on')
  if (newCallback !== callback) {
    callback._wrappedCallback.push(newCallback)
  }
  arguments[1] = newCallback
  return onEvent.apply(this, arguments)
}
var removeEvent = EventEmitter.prototype.removeListener
EventEmitter.prototype.removeListener = function (type, callback) {
  if (callback && Array.isArray(callback._wrappedCallback)) {
    arguments[1] = callback._wrappedCallback.pop()
  }
  return removeEvent.apply(this, arguments)
}

Basically, what I'm doing is still wrapping each callback, but I store the array on the original function so when it comes time to remove I can pop them off the array. This fixes the issue in http.js::onServerResponseClose.