gistfile1.rb

# Wrap a fiber around app_call
Fiber.new{
  # [...]
  # Below is modified from event_machine/client.rb, in def app_call input,
  # but let's forget about :async for now.
  # In APP.call, it would call Fiber.yield whenever we're waiting for data.
  status, headers, body = APP.call(@env.merge!(RACK_DEFAULTS))

  # The response is fully ready at this point.
  ev_write_response(status, headers, body, @hp.next?)
}.resume

# * * * * *

# Here's the app
APP = lambda{ |env|
  # First we remember where we need to jump back
  f = Fiber.current
  # Wait for 5 seconds to emulate waiting for data
  EM.add_timer(5){
    # Here then we have data available, let's resume back.
    # But we also wrap resuming in a next_tick block,
    # giving EM some chances to cleanup it's internal states.
    EM.next_tick{
      f.resume('OK')
    }
  }
  # Here we immediately yield and give control back to Rainbows!
  # and Rainbows! would then go back to EventMachine's regular loop,
  # buffering requests, making requests, etc.
  body = Fiber.yield

  # So now body is referring the data resumed from above.
  # Rainbows! should handle the response at this point.
  [200, {}, [body]]
}