config.ru

#!/usr/bin/env thin -e production -R config.ru -V start
# config.ru
# N.B. Rack::Lint doesn't yet support the api, use production mode rack.

require 'eventmachine'

class AsyncApp
  
  class DeferrableBody
    include EventMachine::Deferrable

    def call(body)
      body.each do |chunk|
        @body_callback.call(chunk)
      end
    end

    def each &blk
      @body_callback = blk
    end

  end
  
  # This is a template async response. N.B. Can't use string for body on 1.9
  AsyncResponse = [-1, {}, []].freeze
    
  def call(env)
    body = DeferrableBody.new
    
    EventMachine::next_tick { env['async.callback'].call [200, {'Content-Type' => 'text/plain'}, body] }
    
    EventMachine::add_periodic_timer(3) do
      body.call ["Cheers then!\n"]
      # body.succeed
    end
    AsyncResponse
  end
  
end

run AsyncApp.new