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Description
Bug report
When a proxy derived from multiprocessing.managers.BaseProxy is passed between processes, the self._manager attribute becomes None. self._manager is however accessed to retrieve its _registry attribute, which contain the method_to_typeid map recorded into the manager viaBaseManager.register(), causing an AttributeError. The solution is to decouple the role of the manager from the role of the registry and propagate the registry separately. I'll submit a pull request to fix this.
Minimal failing example
test.py
from multiprocessing import Process
from multiprocessing.managers import BaseProxy, BaseManager
class Parent(object):
def __init__(self, *args, **kwargs):
pass
def make_child(self):
return Parent()
class MyManager(BaseManager):
pass
def child_generator(parent):
parent.make_child()
if __name__ == "__main__":
MyManager.register('Parent', callable=Parent,
method_to_typeid={'make_child': 'Parent'})
with MyManager() as manager:
parent = manager.Parent()
process = Process(target=child_generator, args=(parent, ))
process.start()
process.join()
Output
❯ python3 test.py
Process Process-2:
Traceback (most recent call last):
File "/usr/local/Cellar/python@3.10/3.10.8/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/process.py", line 314, in _bootstrap
self.run()
File "/usr/local/Cellar/python@3.10/3.10.8/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/process.py", line 108, in run
self._target(*self._args, **self._kwargs)
File "test.py", line 18, in child_generator
parent.make_child()
File "<string>", line 2, in make_child
File "/usr/local/Cellar/python@3.10/3.10.8/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/managers.py", line 824, in _callmethod
proxytype = self._manager._registry[token.typeid][-1]
AttributeError: 'NoneType' object has no attribute '_registry'
Environment
- CPython versions tested on: 3.6, 3.7, 3.8, 3.9, 3.10
- Operating system and architecture: macOS Monterey 12.6
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