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问题描述

我正在尝试从多处理进程中获取跟踪对象。
不幸地通过管道传递异常信息不起作用,因为追溯对象不能被腌制:

I am trying to get hold of a traceback object from a multiprocessing.Process.Unfortunately passing the exception info through a pipe does not work because traceback objects can not be pickled:

def foo(pipe_to_parent):
    try:
        raise Exception('xxx')
    except:
        pipe_to_parent.send(sys.exc_info())

to_child, to_self = multiprocessing.Pipe()
process = multiprocessing.Process(target = foo, args = (to_self,))
process.start()
exc_info = to_child.recv()
process.join()
print traceback.format_exception(*exc_info)
to_child.close()
to_self.close()

追溯:

Traceback (most recent call last):
  File "/usr/lib/python2.6/multiprocessing/process.py", line 231, in _bootstrap
    self.run()
  File "/usr/lib/python2.6/multiprocessing/process.py", line 88, in run
    self._target(*self._args, **self._kwargs)
  File "foo", line 7, in foo
    to_parent.send(sys.exc_info())
PicklingError: Can't pickle <type 'traceback'>: attribute lookup __builtin__.traceback failed

还有另外一种方式来访问异常信息?我想避免传递格式化的字符串。

Is there another way to access the exception info? I'd like to avoid passing the formatted string.

推荐答案

使用你可以传递包装的例外并稍后重新提出:

Using tblib you can pass wrapped exceptions and reraise them later:

import tblib.pickling_support
tblib.pickling_support.install()

from multiprocessing import Pool
import sys


class ExceptionWrapper(object):

    def __init__(self, ee):
        self.ee = ee
        __,  __, self.tb = sys.exc_info()

    def re_raise(self):
        raise self.ee.with_traceback(self.tb)
        # for Python 2 replace the previous line by:
        # raise self.ee, None, self.tb


# example how to use ExceptionWrapper

def inverse(i):
    """will fail for i == 0"""
    try:
        return 1.0 / i
    except Exception as e:
        return ExceptionWrapper(e)


def main():
    p = Pool(1)
    results = p.map(inverse, [0, 1, 2, 3])
    for result in results:
        if isinstance(result, ExceptionWrapper):
            result.re_raise()


if __name__ == "__main__":
    main()

所以,如果你在远程进程中遇到异常,请用 ExceptionWrapper 然后将其传回。在主流程中调用 re_reraise 可以完成工作。

So, if you catch an exception in your remote process, wrap it with ExceptionWrapper and then pass it back. Calling re_reraise in the main process will do the work.

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09-18 01:26