python - 在 Python 中绑定(bind)信号处理程序时，<Finalize object, dead> 中没有属性 '_popen'“

Question

每当继承 mulitprocessing.Process 类并将 SIGCHLD 信号绑定(bind)到其中时，python 解释器会引发以下错误:

Exception AttributeError: "'MyClass' object has no attribute '_popen'" in <Finalize object, dead> ignored

但是我的类(class)有预期的行为。

这是信号处理的样子:

import os 
import signal
import multiprocessing

class Actor(multiprocessing.Process):
    def __init__(self, *args, **kwargs):
        self.bind_signals_handlers()
        ...
        super(Actor, self).__init__(*args, **kwargs)

    def on_children_exit(self):
        """Signal handler to be called on SIGCHLD.

        This handler will be called on every SIGCHLD signal received
        by the actor. SIGCHLD is raised on process interuptions and on
        process death, so you can override this handler to set up
        the behavior you'd like.

        As a default this handler will check if a child process
        as exited, and that's it.
        """
        # Make sure we do the waitpid over the parent process
        # and not from any children.
        # see http://stackoverflow.com/questions/5783183/python-multiprocessing-issue-misunderstanding
        # see http://bugs.python.org/issue9535
        if os.getpid() == self.pid:
            pid, status = os.waitpid(-1, os.WNOHANG)
            if pid:
                print "Actor's child with pid {} exited".format(pid)

    def bind_signals_handlers(self):
        def sig_child_handler(signum, frame):
            self.on_children_exit()
        def sig_shutdown_handler(signum, frame):
            self.stop()

        signal.signal(signal.SIGTERM, sig_shutdown_handler)
        signal.signal(signal.SIGINT, sig_shutdown_handler)
        signal.signal(signal.SIGCHLD, sig_child_handler)

是否知道导致警告的原因以及如何解决？

非常感谢!

Answer 1

我终于通过捕获 AttributeError 并检查回溯找到了解决方案。在 multiprocessing.Process 实例启动之前访问 pid 属性会引发 AttributeError。

我还没有找到任何关于它的文档。