Testing throughput bottlenecks in Goliath from Mongoid gem

Pre-requisites

0. gem install goliath (should be v0.9.4 as of writing this)
1. gem install mongoid (should be v2.3.3 as of writing this)
2. create and save test.rb file (see below)
3. % ruby test.rb -sv
4. % ab -n500 -c10 http://localhost:9000/status
5. note the req/s results (somewhere around 80-90 req/s on my machine)
6. edit the test.rb file, remove the 'require mongoid' line
7. repeat steps 3 and 4.
8. note the req/s results (somewhere aaround 550 req/s on my machine)


Conclusion: Mongoid is patching something in its initialization that is causing severe performance bottlenecks in Goliath.

test.rb

$:<< '../lib' << 'lib'

require 'goliath'
require 'mongoid'

class HelloWorld < Goliath::API
  use Goliath::Rack::Heartbeat

  def response(env)
    [200, {}, ""]
  end
end

(the short version of what I'm puzzling through is how do I know that MongoDB calls are really async... that's where this all started)