Question

我正在尝试使用Ctrl + C优雅地停止运行的代码，包括本地dask.distrubted客户端。下面的代码是我的设置示例。当我使用Ctrl + C时，将正确调用stop（）方法，但是dask Client似乎在到达self.dask.close（）方法之前就不正确地退出/打印了回溯。

from dask.distributed import Client

class SomeService(object):
    def __init__(self):
        self.dask = None

    def run(self):
        # Setup local dask client
        self.dask = Client()

        while True:
            # Do something blocking

    def stop(self):
        # Close dask client
        print('Closing Dask Client...')
        self.dask.close()
        print('Dask Cient closed.')
        # Stop other stuff
        # ...
        print('SomeService has been stopped.')


if __name__ == '__main__':
    service = SomeService()
    try:
        service.run()
    except KeyboardInterrupt:
        print('Keyboard interrupt received.')
        service.stop()

这是我收到的输出：

^CTraceback (most recent call last):
File "<string>", line 1, in <module>
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/multiprocessing/forkserver.py", line 170, in main
rfds = [key.fileobj for (key, events) in selector.select()]
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/selectors.py", line 560, in select
kev_list = self._kqueue.control(None, max_ev, timeout)
KeyboardInterrupt
Keyboard interrupt received.
Closing Dask Client...
Dask Client closed.
SomeService has been stopped.

我已尽力使google / stack溢出此问题，而我发现的唯一解决方案是使用信号包强制回调SIGINT的建议。但是，如果要在单独的线程中运行SomeService类，则此解决方案将不起作用，因为您只能对主线程上的信号强制执行信号回调。

任何建议将不胜感激。这不是保持和管理Dask Client / LocalClient的正确方法吗？

其他信息：

Python 3.5.1
dask==0.19.2
distributed==1.23.2
tornado==5.0.2

Answer 1

使用设置标志的信号处理程序。交付后，将导致IOError异常（将.errno成员设置为errno.EINTR）：

import signal

done = False
def done_handler(signum, frame):
    done = True

if __name__ == '__main__':
    signal.signal(signal.SIGINT, done_handler)

    service = SomeService()

    while not done:
        try:
            service.run()
        except IOError:
            break

    service.stop()

在Python中，信号始终在主线程中传递，并且处理程序始终在主线程中执行，因此，除非捕获到IOError异常，否则它应渗透到service.run()。（在您的示例中，KeyboardInterrupt会这样做。）当捕获到该异常时，服务将停止。

启动dask.distributed Client / LocalClient

1 个答案: