Python:从 multiprocessing.Process 获取回溯 [英] Python: Getting a traceback from a multiprocessing.Process
问题描述
我正在尝试从 multiprocessing.Process 中获取回溯对象.不幸的是,通过管道传递异常信息不起作用,因为无法腌制回溯对象:
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
还有其他方法可以访问异常信息吗?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 tblib代码>
您可以传递包装的异常并在以后重新提出它们:
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 of 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()
因此,如果您在远程进程中捕获异常,请使用 ExceptionWrapper
将其包装起来,然后将其传回.在主进程中调用 re_raise()
将完成这项工作.
So, if you catch an exception in your remote process, wrap it with ExceptionWrapper
and then pass it back. Calling re_raise()
in the main process will do the work.
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