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我的同事要求我的帮助,他遇到了一个他正在使用的守护进程脚本的问题。他是有一个奇怪的错误涉及multiprocessing.Manager,我成功地再现与以下五类线:Python multiprocessing.manager和os.fork产生奇怪的行为
import multiprocessing, os, sys
mgr = multiprocessing.Manager()
pid = os.fork()
if pid > 0:
sys.exit(0)
当在CentOS 6 Linux和Python 2.6中运行时,我收到以下错误:
Traceback (most recent call last):
File "/usr/lib64/python2.6/multiprocessing/util.py", line 235, in _run_finalizers
finalizer()
File "/usr/lib64/python2.6/multiprocessing/util.py", line 174, in __call__
res = self._callback(*self._args, **self._kwargs)
File "/usr/lib64/python2.6/multiprocessing/managers.py", line 576, in _finalize_manager
if process.is_alive():
File "/usr/lib64/python2.6/multiprocessing/process.py", line 129, in is_alive
assert self._parent_pid == os.getpid(), 'can only test a child process'
AssertionError: can only test a child process
Error in atexit._run_exitfuncs:
Traceback (most recent call last):
File "/usr/lib64/python2.6/atexit.py", line 24, in _run_exitfuncs
func(*targs, **kargs)
File "/usr/lib64/python2.6/multiprocessing/util.py", line 269, in _exit_function
p.join()
File "/usr/lib64/python2.6/multiprocessing/process.py", line 117, in join
assert self._parent_pid == os.getpid(), 'can only join a child process'
AssertionError: can only join a child process
Error in sys.exitfunc:
Traceback (most recent call last):
File "/usr/lib64/python2.6/atexit.py", line 24, in _run_exitfuncs
func(*targs, **kargs)
File "/usr/lib64/python2.6/multiprocessing/util.py", line 269, in _exit_function
p.join()
File "/usr/lib64/python2.6/multiprocessing/process.py", line 117, in join
assert self._parent_pid == os.getpid(), 'can only join a child process'
AssertionError: can only join a child process
我怀疑这个错误是由os.fork和multiprocessing.Manager之间的一些交互造成的,他应该使用多处理模块来创建新的进程而不是os.fork。任何人都可以证实这一点和/或解释发生了什么?如果我的预感是正确的,为什么这是错误的地方使用os.fork?
'Manager'总是创建一个处理共享内存的新进程,所以似乎有一些交互。现在我无法确切地告诉你为什么会发生这种情况,以及如何使用'os.fork'来解决这个问题。我必须同意,应该避免使用'os.fork',因为它真的是*低级*。应该有一些使用'multiprocessing'的方法。 – Bakuriu