芹菜从 task_success 处理程序中关闭工人不起作用

Question

我试图让工作人员一次只运行一项任务，然后关闭。我的关机部分工作正常（这里有一些背景：celery trying shutdown worker by raising SystemExit in task_postrun signal but always hangs and the main process never exits），但是当它关​​机时，我收到一个错误：

[2013-02-13 12:19:05,689: CRITICAL/MainProcess] Couldn't ack 1, reason:AttributeError("'NoneType' object has no attribute 'method_writer'",)
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/kombu/transport/base.py", line 104, in ack_log_error
    self.ack()
  File "/usr/local/lib/python2.7/site-packages/kombu/transport/base.py", line 99, in ack
    self.channel.basic_ack(self.delivery_tag)
  File "/usr/local/lib/python2.7/site-packages/amqplib/client_0_8/channel.py", line 1742, in basic_ack
    self._send_method((60, 80), args)
  File "/usr/local/lib/python2.7/site-packages/amqplib/client_0_8/abstract_channel.py", line 75, in _send_method
    self.connection.method_writer.write_method(self.channel_id,
AttributeError: 'NoneType' object has no attribute 'method_writer'

为什么会这样？它不仅不确认，而且还会清除队列中剩余的所有其他任务（大问题）。

我该如何解决这个问题？

更新

下面是所有更新的堆栈跟踪（pip install -U kombu amqp amqplib celery）：

[2013-02-13 11:58:05,357: CRITICAL/MainProcess] Internal error: AttributeError("'NoneType' object has no attribute 'method_writer'",)
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/celery/worker/__init__.py", line 372, in process_task
    req.execute_using_pool(self.pool)
  File "/usr/local/lib/python2.7/dist-packages/celery/worker/job.py", line 219, in execute_using_pool
    timeout=task.time_limit)
  File "/usr/local/lib/python2.7/dist-packages/celery/concurrency/base.py", line 137, in apply_async
    **options)
  File "/usr/local/lib/python2.7/dist-packages/celery/concurrency/base.py", line 27, in apply_target
    callback(target(*args, **kwargs))
  File "/usr/local/lib/python2.7/dist-packages/celery/worker/job.py", line 333, in on_success
    self.acknowledge()
  File "/usr/local/lib/python2.7/dist-packages/celery/worker/job.py", line 439, in acknowledge
    self.on_ack(logger, self.connection_errors)
  File "/usr/local/lib/python2.7/dist-packages/kombu/transport/base.py", line 98, in ack_log_error
    self.ack()
  File "/usr/local/lib/python2.7/dist-packages/kombu/transport/base.py", line 93, in ack
    self.channel.basic_ack(self.delivery_tag)
  File "/usr/local/lib/python2.7/dist-packages/amqp/channel.py", line 1562, in basic_ack
    self._send_method((60, 80), args)
  File "/usr/local/lib/python2.7/dist-packages/amqp/abstract_channel.py", line 57, in _send_method
    self.connection.method_writer.write_method(
AttributeError: 'NoneType' object has no attribute 'method_writer'

Answer 1

不建议在 task_postrun 中退出，因为 task_postrun 是在“任务主体”错误处理之外执行的。

当一个任务调用 sys.exit 时发生的事情没有明确定义， 实际上这取决于正在使用的池。

使用多处理，子进程将简单地被一个新进程替换。 在其他池中，工作人员将关闭，但这可能会改变 使其与多处理行为一致。

在任务体之外调用exit被认为是内部错误（crash）。

“任务主体”是在 task.__call__() 处执行的任何内容

我认为可能更好的解决方案是使用自定义执行 策略：

from celery.worker import strategy
from functools import wraps

@staticmethod
def shutdown_after_strategy(task, app, consumer):

    default_handler = strategy.default(task, app, consumer)

    def _shutdown_to_exit_after(fun):
        @wraps(fun)
        def _inner(*args, **kwargs):
            try:
                return fun(*args, **kwargs)
            finally:
                raise SystemExit()
       return _inner
    return _decorate_to_exit_after(default_handler)

@celery.task(Strategy=shutdown_after_strategy)
def shutdown_after():
    print('will shutdown after this')

这不是很漂亮，但执行策略可以优化 任务执行并且不容易扩展（工作人员“预编译”执行 通过缓存Task.Strategy为每个任务类型的路径）

在 Celery 3.1 中，您可以使用“bootsteps”扩展工作人员和消费者，很可能 那么会有一个很好的解决方案。