Question

我有一个以下代码，如果完成时间过长，应该启动一个作业并终止该过程。

import random
from datetime import datetime
from subprocess import check_output, STDOUT, TimeoutExpired

MAX_WAIT = 5

def custom_task(job=None):
    sec = job or random.randint(4,10)
    print('\nThis task will sleep {s} sec.'.format(s=sec))
    print('-/- {time} - - Commence new job <{job}>'.format(
             job=sec, time=datetime.now()))
    try:
        cmd = 'sleep {s}; echo "Woke up after {s} sec." | tee -a task.log'.format(s=sec)
        stdout = check_output(cmd, shell=True, stderr=STDOUT, timeout=MAX_WAIT).decode()
    except TimeoutExpired:
        print('~/~ {time} - - Job <{job}> has been cancelled'.format(
                 job=sec, time=datetime.now()))
    except Exception as err:
        print('!/! {time} - - Job <{job}> could not finish because of the error'.format(
                 job=sec, time=datetime.now()))
        print('{err}'.format(err=err))
    else:
        print('=/= {time} - - Job <{job}> has been done'.format(
                 job=sec, time=datetime.now()))
        print(stdout)

custom_task(4)
custom_task(8)

控制台为我提供了以下输出：

This task will sleep 4 sec.
-/- 2016-11-03 01:07:56.037104 - - Commence new job <4>
=/= 2016-11-03 01:08:00.051072 - - Job <4> has been done
Woke up after 4 sec.


This task will sleep 8 sec.
-/- 2016-11-03 01:08:00.051233 - - Commence new job <8>
~/~ 2016-11-03 01:08:08.062563 - - Job <8> has been cancelled

请注意，应该睡8秒的任务在8秒后释放阻止，而不是在预期MAX_WAIT = 5

之后

但如果我检查tasks.log，我会看到：

Woke up after 4 sec.

这意味着只有4秒的任务已成功完成，这是期望和预期的。因此，我的脚本有点工作，但是以相当意外和不受欢迎的方式。

有没有办法按时释放阻止（杀死进程），因此只要超过MAX_WAIT超时？

这里发生了什么，为什么python等到sleep完成睡眠？

编辑 - 工作示例

from random import randint
from os import killpg
from signal import SIGKILL
from datetime import datetime
from subprocess import Popen, STDOUT, TimeoutExpired, PIPE

MAX_WAIT = 5

def custom_task(job=None):
    sec = job or randint(4,10)
    print('\n# This task will sleep {s} sec.'.format(s=sec))
    print('-/- {time} - - Commence new job <{job}>'.format(
          job=sec, time=datetime.now()))
    cmd = 'sleep {s}; echo "Woke up after {s} sec." | tee -a tasks.log'.format(s=sec)
    with Popen(cmd, shell=True,
               stdout=PIPE, stderr=STDOUT,
               close_fds=True,
               universal_newlines=True,
               start_new_session=True) as proc:
        try:
            stdout = proc.communicate(timeout=MAX_WAIT)[0]
        except TimeoutExpired:
            print('~/~ {time} - - Job <{job}> has been cancelled'.format(
                  job=sec, time=datetime.now()))
            killpg(proc.pid, SIGKILL)
            stdout = proc.communicate(timeout=1)[0]
        except Exception as err:
            print('!/! {time} - - Job <{job}> could not finish because of the error'.format(
                  job=sec, time=datetime.now()))
            print('{err}'.format(err=err))
            killpg(proc.pid, SIGKILL)
        else:
            print('=/= {time} - - Job <{job}> has been done'.format(
                  job=sec, time=datetime.now()))
        print('# Return code: {}'.format(proc.returncode))
        print(stdout)

custom_task(4)
custom_task(30)

输出的

$ time python3 popen.py 

# This task will sleep 4 sec.
-/- 2016-11-05 15:38:13.833871 - - Commence new job <4>
=/= 2016-11-05 15:38:17.842769 - - Job <4> has been done
# Return code: 0
Woke up after 4 sec.


# This task will sleep 30 sec.
-/- 2016-11-05 15:38:17.842942 - - Commence new job <30>
~/~ 2016-11-05 15:38:22.849511 - - Job <30> has been cancelled
# Return code: -9


real    0m9.095s
user    0m0.087s
sys 0m0.000s

Answer 1

check_output调用实际上有几个进程被调用。因此，当subprocess发送kill信号时，它不会被发送到所有后代进程。 check_output可能会等待其他进程完成。有关解决方案，请查看StackOverflow上的post。

延迟超时进程终止的subprocess.check_output

1 个答案: