Python3 asyncio"任务被破坏,但它正在等待"具有一些特定条件

Question

这是简化的代码,它使用python3协同程序并为SIGING和SIGTERM信号设置处理程序以正确停止作业:

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import argparse
import asyncio
import signal
import sys


def my_handler(signum, frame):
    print('Stopping')
    asyncio.get_event_loop().stop()
    # Do some staff
    sys.exit()


@asyncio.coroutine
def prob_ip(ip_addr):

    print('Ping ip:%s' % ip_addr)
    proc = yield from asyncio.create_subprocess_exec('ping', '-c', '3', ip_addr)
    ret_code = yield from proc.wait()
    if ret_code != 0:
        print("ip:%s doesn't responding" % ip_addr)
        # Do some staff
        yield from asyncio.sleep(2)
        # Do more staff
        yield from asyncio.sleep(16)


@asyncio.coroutine
def run_probing():

    print('Start probing')
    # Do some staff
    yield from asyncio.sleep(1)

    while True:
        yield from asyncio.wait([prob_ip('192.168.1.3'), prob_ip('192.168.1.2')])
        yield from asyncio.sleep(60)


def main():
    parser = argparse.ArgumentParser()
    parser.description = "Probing ip."
    parser.parse_args()

    signal.signal(signal.SIGINT, my_handler)
    signal.signal(signal.SIGTERM, my_handler)

    asyncio.get_event_loop().run_until_complete(run_probing())


if __name__ == '__main__':
    main()

当我通过以下方式运行时:

python3 test1.py

它由Ctrl-C停止,没有任何警告.但当我通过以下方式运行时:

python3 -m test1

它通过Ctrl-C打印警告:

$ python3 -m test1 
Start probing
Ping ip:192.168.1.2
Ping ip:192.168.1.3
PING 192.168.1.2 (192.168.1.2): 56 data bytes
PING 192.168.1.3 (192.168.1.3): 56 data bytes
^C--- 192.168.1.2 ping statistics ---
--- 192.168.1.3 ping statistics ---
1 packets transmitted, 0 packets received, 100% packet loss
1 packets transmitted, 0 packets received, 100% packet loss
Stopping
Task was destroyed but it is pending!
task: <Task pending coro=<prob_ip() running at /tmp/test1.py:22> wait_for=<Future pending cb=[Task._wakeup()]> cb=[_wait.<locals>._on_completion() at /usr/lib/python3.4/asyncio/tasks.py:394]>
Task was destroyed but it is pending!
task: <Task pending coro=<prob_ip() running at /tmp/test1.py:22> wait_for=<Future pending cb=[Task._wakeup()]> cb=[_wait.<locals>._on_completion() at /usr/lib/python3.4/asyncio/tasks.py:394]>

如果我通过以下方式安装此脚本,则会收到相同

from setuptools import setup

setup(name='some_scripts',
      version='1.0.0.0',
      author='Some Team',
      author_email='team@team.ru',
      url='https://www.todo.ru',
      description='Some scripts',
      packages=['my_package'],
      entry_points={'console_scripts': [
          'test1=my_package.test1:main',
      ]},
      )

我的python版本是"3.4.2"

Answer 1

好.我想我已经弄清楚应该如何停止所有任务.

1. 首先,据我了解.BaseEventLoop.stop()仅用于停止BaseEventLoop.run_forever().所以应该通过Future.cancel取消所有任务.要获取所有任务,可以使用Task.all_tasks静态方法.
2. 取消后,将从run_until_complete引发所有任务asyncio.CancelledError异常.如果一个人不想将它打印到stderr,那么应该抓住它.

3. 而且,在某些情况下,我收到此错误:TypeError: signal handler must be signal.SIG_IGN, signal.SIG_DFL, or a callable object.我发现了一些关于此错误的主题:

   • https://bugs.python.org/issue23548
   • https://github.com/buildinspace/peru/issues/98

   他们都说可以通过在退出应用程序之前关闭循环来修复它.

所以我们得到这个代码:

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import asyncio
import signal


def my_handler():
    print('Stopping')
    for task in asyncio.Task.all_tasks():
        task.cancel()


@asyncio.coroutine
def do_some(some_args):
    while True:
        print("Do staff with %s" % some_args)
        yield from asyncio.sleep(2)


def main():
    loop = asyncio.get_event_loop()

    loop.add_signal_handler(signal.SIGINT, my_handler)

    try:
        loop.run_until_complete(asyncio.wait([do_some(1), do_some(2)]))
    except asyncio.CancelledError:
        print('Tasks has been canceled')
    finally:
        loop.close()


if __name__ == '__main__':
    main()

它也适用于signal.signal.但正如Vincent 注意到 loop.add_signal_handler在这种情况下看起来更好.

但我仍然不确定这是停止所有任务的最佳方法.

Answer 2

使用asyncio.gather代替asyncio.wait:

取消:如果取消外部未来,所有子女(尚未完成)也将被取消.

例:

def handler(future, loop):
    future.cancel()
    loop.stop()

@asyncio.coroutine
def do_some(arg):
    while True:
        print("Do stuff with %s" % arg)
        yield from asyncio.sleep(2)

loop = asyncio.get_event_loop()
future = asyncio.gather(do_some(1), do_some(2))
loop.add_signal_handler(signal.SIGINT, handler, future, loop)
loop.run_forever()