如何在 async def 函数中正确使用 asyncio.create_subprocess_shell()？

Question

我正在尝试编写一个简单的子进程程序，它将调用一个长时间运行的 shell 命令，允许其他进程运行，然后在完成后执行一些清理任务。

不幸的是，我遇到了错误，只是让 shell 命令在 asyncio 事件循环中正确执行。行为是它看起来 python 从不等待 shell 脚本完成运行。我知道 shell 脚本可以工作，因为我可以从提示符手动运行它。我正在运行的 shell 脚本应该在大约 3-5 分钟内执行。

这是我的示例程序：

import asyncio 
from asyncio.subprocess import PIPE, STDOUT 
import subprocess 
import signal


def signal_handler(signal, frame):
    loop.stop()
    client.close()
    sys.exit(0)

async def run_async(loop = ''):
    cmd = 'sudo long_running_cmd --opt1=AAAA --opt2=BBBB'

    print ("[INFO] Starting script...")
    await asyncio.create_subprocess_shell(cmd1, stdin = PIPE, stdout = PIPE, stderr = STDOUT)
    print("[INFO] Script is complete.")


loop = asyncio.get_event_loop() 
signal.signal(signal.SIGINT, signal_handler) 
tasks = [loop.create_task(run_async())] 
wait_tasks = asyncio.wait(tasks) 
loop.run_until_complete(wait_tasks)

loop.close()

该程序几乎立即运行并失败。此代码生成的错误是：

[INFO] Starting script...
[INFO] Script is complete.
Exception ignored in: <bound method BaseSubprocessTransport.__del__ of <_UnixSubprocessTransport closed pid=5652 running stdin=<_UnixWritePipeTransport closing fd=7 open> stdout=<_UnixReadPipeTransport fd=8 open>>>
Traceback (most recent call last):
  File "/usr/lib/python3.5/asyncio/base_subprocess.py", line 126, in __del__
  File "/usr/lib/python3.5/asyncio/base_subprocess.py", line 101, in close
  File "/usr/lib/python3.5/asyncio/unix_events.py", line 568, in close
  File "/usr/lib/python3.5/asyncio/unix_events.py", line 560, in write_eof
  File "/usr/lib/python3.5/asyncio/base_events.py", line 497, in call_soon
  File "/usr/lib/python3.5/asyncio/base_events.py", line 506, in _call_soon
  File "/usr/lib/python3.5/asyncio/base_events.py", line 334, in _check_closed
RuntimeError: Event loop is closed

我在 Ubuntu 16.04 上运行 python v3.5.2。

更新

根据下面 Sam 的评论，我需要将我的代码更新为以下内容才能使其正常工作：

process = await asyncio.create_subprocess_shell(cmd1, stdin = PIPE, stdout PIPE, stderr = STDOUT)
await process.wait()

这是对他的代码的轻微修改，但有效。

Answer 1

问题是没有任何东西等待进程完成；你只等它开始。

async def run_async(loop = ''):
    cmd = 'sudo long_running_cmd --opt1=AAAA --opt2=BBBB'

    print ("[INFO] Starting script...")
    process = await asyncio.create_subprocess_shell(cmd1, stdin = PIPE, stdout = PIPE, stderr = STDOUT)
    await process.wait()
    print("[INFO] Script is complete.")