def _sync(pack):
    """Simulate a package travelling through the cluster."""
    task_queue = Queue()
    result_queue = Queue()
    task = SignedPackage.loads(pack)
    task_queue.put(task)
    task_queue.put('STOP')
    worker(task_queue, result_queue, Value('f', -1))
    result_queue.put('STOP')
    monitor(result_queue)
    task_queue.close()
    task_queue.join_thread()
    result_queue.close()
    result_queue.join_thread()
    return task['id']
Simulate a package travelling through the cluster.