I am working on a smallish web framework for serving web services, totally asynchronously.A Sample controller looks like this:

class HomeController < MsfService::Controller
  def index
    request_lamda = lambda do |t|
      t.quote("IBM")
    end
    response_lambda = lambda do |quote|
      @ready_to_render = true
      render :html => "#{quote.last}"
    end
    backend_server.defer(request_lamda,response_lambda)
  end
end

In a word when data request in request proc is ready then only view is rendered. So, I can't invoke call then and there as rack specification requires and hence I have modified thin a bit so as:

    def process
      @request.threaded = false
      pre_process
    end

    def pre_process
      # Add client info to the request env
      @request.remote_address = remote_address

      # Process the request calling the Rack adapter
      @app.call(@request.env) do |result|
        post_process(result)
      end
    rescue Object
      handle_error
      terminate_request
      post_process(nil) # Signal to post_process that the request could not be processed
    end

Originally post_process immediately gets called after pre_process, but here I am attaching post_process as a lambda so as it gets called only when response is ready. Above code works, but it partially breaks rack. I am unable to use CommonLogger or other helper classes.