2 different approaches to locking jobs in queue_classic

exp_backoff.rb

def lock_job
  attempts = 0
  job = nil
  until job
    job = @queue.dequeue
    if job.nil?
      attempts += 1
      if attempts < MAX_LOCK_ATTEMPTS
        sleep(2**attempts)
        next
      else
        break
      end
    end
  end
  job
end

listen_notify.rb

def lock_job
  job = nil
  until job
    if job = @queue.dequeue
      @queue.database.unlisten
    else
      @queue.database.listen
      @queue.database.wait_for_notify
    end
  end
  job
end