Ruby: async & thread pool under one EventMachine server

README.md

Imagine if you could run a synchronous Rack app (maybe Rails) on a thread pool and an asynchronous one under one server? Celluloid to the rescue!

In this example, both sync and async versions have (almost) equal concurrency under siege -b (running on Rubinius).

config.ru

require 'celluloid/autostart'

SIMULATED_TIME = 0.2
PAYLOAD = [200, {'Content-Type' => 'text/plain'}, ['Hello']]

class SyncApp
  def call(env)
    sleep SIMULATED_TIME
    PAYLOAD
  end
end

class AsyncApp
  def call(env)
    EM.add_timer(SIMULATED_TIME) do
      env['async.callback'].call PAYLOAD
    end
    throw :async
  end
end

class SyncAppCell < SyncApp
  include Celluloid

  def call(env)
    env['async.callback'].call super(env)
  end
end

sac_pool = SyncAppCell.pool size: 16

map '/sync' do
  run lambda { |env|
    sac_pool.async.call env
    throw :async
  }
end

map '/async' do
  run AsyncApp.new
end

Gemfile

source 'http://rubygems.org'

gem 'thin'
gem 'celluloid'