In-process EM.spawn for Sinatra app

app.rb

require 'sinatra/base'

module FavIcon
  class Service < Sinatra::Base

    configure do
      set :app_file, __FILE__
      set :root, File.expand_path(File.join(File.dirname(__FILE__), '..','..'))
      set :server, %w[thin mongrel webrick]
      set :logging, true
      set :raise_errors, false
      set :show_exceptions, false
      set :run, false
      set :cache_dir, ENV['FAVICON_CACHE_DIR'] || File.expand_path(File.join(File.dirname(__FILE__), '..', '..', 'cache'))
      set :logger, FavIcon::LOGGER
      set :default_icon, "#{cache_dir}/default.png"
    end

    configure(:development) do
      begin
        require 'sinatra/reloader'
        register Sinatra::Reloader
      rescue LoadError
        settings.logger.warn("sinatra-reloader gem missing. reloading disabled")
      end
    end

    not_found do
      content_type 'image/png'
      File.read(settings.default_icon)
    end

    error do
      content_type 'image/png'
      File.read(settings.default_icon)
    end

    get '/favicon.ico' do
      content_type 'image/png'
      File.read(settings.default_icon)
    end

    get '/:url' do |url|
      content_type "image/png"
      (url =~ /^www\..*/).nil? ? url=url : url=url.gsub(/^www\.(.*)/,'\1')
      file_name = "#{url}.favicon.png"
      icon = File.join(settings.cache_dir, file_name)
      if File.exists?(icon)
        File.read(icon)
      else
        EM.reactor_running? ? settings.worker.notify(url) : settings.logger.warn("Reactor not running")
        File.read(settings.default_icon)
      end
    end

  end
end

EM.spawn_Thin.rb

#!/usr/bin/env ruby
$:.unshift(File.expand_path(File.join(File.dirname(__FILE__), "..", "lib")))
require 'eventmachine'
require 'thin'
require 'favicon_service'
require 'favicon_service/app'

EventMachine.run do
  grabber = EM.spawn {|url|
		# Do some stuff with url
  }
  app = FavIcon::Service # This is my sinatra/base app
  app.set :worker, grabber
	Thin::Server.start('0.0.0.0', 9292, app)
end

This will sort of fall apart if you use rackup w/Thin because Thin IS running in a reactor. For robustness, you should define a default "settings.worker" fallback to be used if running under, say, webrick.