为什么主进程和子进程在主进程发生异常后不退出？

Question

#coding=utf8
from multiprocessing import Process
from time import sleep
import os 

def foo():
    print("foo")
    for i in range(11000):
        sleep(1)
        print("{}: {}".format(os.getpid(), i))


if __name__ == "__main__":
    p = Process(target=foo)
    #p.daemon = True
    p.start()
    print("parent: {}".format(os.getpid()))
    sleep(20)
    raise Exception("invalid")

主进程抛出异常，子进程和主进程保持运行。为什么？

Answer 1

当 MainProcess 关闭时，non-daemonic 子进程只是加入。这发生在 _exit_function() 中，它注册了 atexit.register(_exit_function)。有兴趣的可以去multiprocessing.util.py查一查

您还可以在开始进程之前插入 multiprocessing.log_to_stderr(logging.DEBUG) 以查看日志消息：

parent: 9670
foo
[INFO/Process-1] child process calling self.run()
9675: 0
9675: 1
...
9675: 18
Traceback (most recent call last):
  File "/home/...", line 26, in <module>
    raise Exception("invalid")
Exception: invalid
[INFO/MainProcess] process shutting down
[DEBUG/MainProcess] running all "atexit" finalizers with priority >= 0
[INFO/MainProcess] calling join() for process Process-1
9675: 19

为什么主进程和子进程在主进程发生异常后不退出？

Why do main- and child-process not exit after exception in main?

python

exception

multiprocessing

python-multiprocessing