run.md

$ node server.js

output in terminal shows that req.foo is no longer sitting in the heap:

got request with a foo of length 10000000
hello world
got request with a foo of length 0
hello world
{ before:
   { nodes: 87105,
     time: Wed Mar 05 2014 15:04:07 GMT-0800 (PST),
     size_bytes: 7986496,
     size: '7.62 mb' },
  after:
   { nodes: 68490,
     time: Wed Mar 05 2014 15:04:13 GMT-0800 (PST),
     size_bytes: 7569112,
     size: '7.22 mb' },
  change:
   { size_bytes: -417384,
     size: '-407.6 kb',
     freed_nodes: 22053,
     allocated_nodes: 3438,
     details:
      [ [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object] ] } }

server.js

var _ = require('underscore');
var assert = require('assert');
var express = require('express');
var memwatch = require('memwatch');
var quest = require('quest');

var app = express()

var checkFoo = function (req) {
  console.log('got request with a foo of length', (req.foo || []).length);
};

app.get("/foo", function(req, res, next) {
  req.foo = _.range(10000000); // allocate a ton of space
  checkFoo(req);
  res.write("hello world");
  res.end();
});

app.get("/no_foo", function(req, res, next) {
  checkFoo(req);
  res.write("hello world");
  res.end();
});

var server = app.listen(5001);

var snapshot = new memwatch.HeapDiff();

var checkHeap = function() {
  memwatch.gc();
  var diff = snapshot.end();
  console.log(diff);
};

quest('http://localhost:5001/foo', function(err, resp, body) {
  assert.ifError(err);
  console.log(body);
  quest('http://localhost:5001/no_foo', function(err, resp, body) {
    assert.ifError(err);
    console.log(body);
    setTimeout(checkHeap, 5000);
  });
});