long_running_tasks.rb

class LongRunningTasks
  include Queueable

  queue 'myqueue'

  def download(url)
    require 'open-uri'
    open("#{RAILS_ROOT}/tmp/#{Time.now.to_i}", 'w+') { |f| f.write(open(url).read) }
  end

end

# From client code...
LongRunningTasks.fire_download 'http://www.google.com/'

queueable.rb

module Queueable

  def self.included(target)
    target.extend(ClassMethods)
  end
  
  # Called-back by queue manager with deserialized message
  def call(task)
    begin
      send(task[:method], *task[:args])
    rescue => e
      # Hook for exception notification
    end
  end
  
  module ClassMethods
    def queue(value=nil)
      if value
        @queue = value
        register!
      else
        @queue
      end
    end
    
    def register!
      JRuby::Rack::Queues.register_listener(self.queue, self)
    end
        
    def method_missing(method, *args)
      super unless method.to_s.match /^fire_/
      task = {
        :method => method.to_s.sub(/^fire_/, ''),
        :args   => args
      }
      fire(task)
    end
    
    def fire(task)
      JRuby::Rack::Queues.send_message(self.queue, task)
    end    
  end

end