New submission from Jerry Chen <jerryc...@gmail.com>:
I am not sure if this is a bug or an expected case.
Long story short, I tried to print the content of a
`multiprocessing.Manager().dict()` in the main thread, but I got a strange
error.
I encountered this error only when the number of pools is rather large (>20)
and only on `macOS` (works perfectly on `Linux`).
Specs:
```
CPU: Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
macOS: 11.2.3
```
The minimum err code is attached:
```python3
#!/usr/bin/env python3
from contextlib import suppress
import multiprocessing as mp
import time
def run():
D[mp.current_process().name] = 'some val'
time.sleep(0.5)
if __name__ == '__main__':
mp.set_start_method('fork')
D, rets = mp.Manager().dict(), []
with mp.Pool(25) as p:
for _ in range(33):
rets.append(p.apply_async(run))
while rets:
for ret in rets[:]:
with suppress(mp.TimeoutError):
ret.get(timeout=0)
rets.remove(ret)
print(len(D))
```
Error:
```
multiprocessing.pool.RemoteTraceback:
"""
Traceback (most recent call last):
File
"/usr/local/Cellar/python@3.9/3.9.2_4/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/managers.py",
line 801, in _callmethod
conn = self._tls.connection
AttributeError: 'ForkAwareLocal' object has no attribute 'connection'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File
"/usr/local/Cellar/python@3.9/3.9.2_4/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/pool.py",
line 125, in worker
result = (True, func(*args, **kwds))
File "/Users/???", line 9, in run
D[mp.current_process().name] = 'some val'
File "<string>", line 2, in __setitem__
File
"/usr/local/Cellar/python@3.9/3.9.2_4/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/managers.py",
line 805, in _callmethod
self._connect()
File
"/usr/local/Cellar/python@3.9/3.9.2_4/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/managers.py",
line 792, in _connect
conn = self._Client(self._token.address, authkey=self._authkey)
File
"/usr/local/Cellar/python@3.9/3.9.2_4/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/connection.py",
line 507, in Client
c = SocketClient(address)
File
"/usr/local/Cellar/python@3.9/3.9.2_4/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/connection.py",
line 635, in SocketClient
s.connect(address)
ConnectionRefusedError: [Errno 61] Connection refused
"""
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/Users/???", line 22, in <module>
ret.get(timeout=0)
File
"/usr/local/Cellar/python@3.9/3.9.2_4/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/pool.py",
line 771, in get
raise self._value
ConnectionRefusedError: [Errno 61] Connection refused
```
----------
components: macOS
messages: 390468
nosy: jerryc443, ned.deily, ronaldoussoren
priority: normal
severity: normal
status: open
title: Possible race condition on multiprocessing.Manager().dict() on macOS
type: behavior
versions: Python 3.9
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue43768>
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