捕获Ctrl + C/SIGINT并在python中正常退出多进程

Question

如何在多进程python程序中捕获Ctrl + C并优雅地退出所有进程,我需要解决方案在unix和windows上工作.我尝试过以下方法:

import multiprocessing
import time
import signal
import sys

jobs = []

def worker():
    signal.signal(signal.SIGINT, signal_handler)
    while(True):
        time.sleep(1.1234)
        print "Working..."

def signal_handler(signal, frame):
    print 'You pressed Ctrl+C!'
    # for p in jobs:
    #     p.terminate()
    sys.exit(0)

if __name__ == "__main__":
    for i in range(50):
        p = multiprocessing.Process(target=worker)
        jobs.append(p)
        p.start()

它有点工作,但我不认为这是正确的解决方案.

编辑: 这可能与此重复

Answer 1

先前接受的解决方案具有竞争条件,并且不起作用map和async功能.

处理Ctrl + C/SIGINTwith 的正确方法multiprocessing.Pool是:

1. SIGINT在Pool创建流程之前忽略流程.这种方式创建了子进程继承SIGINT处理程序.
2. 创建完成SIGINT后,在父进程中还原原始处理程序Pool.
3. 使用map_async而apply_async不是阻止map和apply.
4. 等待结果超时,因为默认阻塞等待忽略所有信号.这是Python bug https://bugs.python.org/issue8296.

把它放在一起:

#!/bin/env python
from __future__ import print_function

import multiprocessing
import os
import signal
import time

def run_worker(delay):
    print("In a worker process", os.getpid())
    time.sleep(delay)

def main():
    print("Initializng 2 workers")
    original_sigint_handler = signal.signal(signal.SIGINT, signal.SIG_IGN)
    pool = multiprocessing.Pool(2)
    signal.signal(signal.SIGINT, original_sigint_handler)
    try:
        print("Starting 2 jobs of 5 seconds each")
        res = pool.map_async(run_worker, [5, 5])
        print("Waiting for results")
        res.get(60) # Without the timeout this blocking call ignores all signals.
    except KeyboardInterrupt:
        print("Caught KeyboardInterrupt, terminating workers")
        pool.terminate()
    else:
        print("Normal termination")
        pool.close()
    pool.join()

if __name__ == "__main__":
    main()

正如@YakovShklarov所指出的那样,在忽略信号和在父进程中取消它之间存在一段时间窗口,在此期间信号可能会丢失.pthread_sigmask相反,使用临时阻止父进程中的信号传递可以防止信号丢失,但是,它在Python-2中不可用.

Answer 2

解决方案基于此链接和此链接,它解决了问题,我不得不转移到Pool:

import multiprocessing
import time
import signal
import sys

def init_worker():
    signal.signal(signal.SIGINT, signal.SIG_IGN)

def worker():
    while(True):
        time.sleep(1.1234)
        print "Working..."

if __name__ == "__main__":
    pool = multiprocessing.Pool(50, init_worker)
    try:
        for i in range(50):
            pool.apply_async(worker)

        time.sleep(10)
        pool.close()
        pool.join()

    except KeyboardInterrupt:
        print "Caught KeyboardInterrupt, terminating workers"
        pool.terminate()
        pool.join()

Answer 3

只需处理工作进程中的KeyboardInterrupt-SystemExit异常:

def worker():
    while(True):
        try:
            msg = self.msg_queue.get()
        except (KeyboardInterrupt, SystemExit):
            print("Exiting...")
            break