queue.rb

# RAILS_ROOT/lib/jobs/queue.rb

module Jobs
  module Queue
    mattr_accessor :logger

    def enqueue(*args)
      Resque.enqueue(self, *args)
    end

    def queued?(*args)
      Resque.queued?(self, *args)
    end

    def error(id, message)
      logger.error("#{Time.now} - #{name} [#{id}] - #{message}")
    end

    def debug(id, message)
      logger.debug("#{Time.now} - #{name} [#{id}] - #{message}")
    end
  end
end

user_signup.rb

# RAILS_ROOT/lib/jobs/mailing/user_signup.rb

module Jobs
  module Mailing
    class UserSignup
      extend ::Jobs::Queue

      @queue = :mailing
      
      def self.perform(user_id)
        unless user = User.find_by_id(user_id)
          error(user_id, "Cannot find user!")
          return
        end

        if user.active?
          error(user_id, "User already activated!")
          return
        end

        debug(user_id, "Sending signup notification email...")

        Mailer::User.deliver_signup_notification(user)

        debug(user_id, "Done!")
      end
    end
  end
end