Forking Redis Object Bug

[jackhart]

Version: redis==4.3.3

Platform: ProductName: Mac OS X ProductVersion: 10.15.7 BuildVersion: 19H1922

Description: Based on my interpretation of the documentation of the ProcessPool class, there was intention to support forking. This does not work as expected for me. Python is unable to serialize the "_lock" object in the ProcessPool, which is a thread lock, not a process lock.

import multiprocessing as mp
import redis


def run_method(redis_pool):
    print("hello!")


def run() -> str:
    """Get the username"""

    # you can use either of these objects.  Creates same error.
    # redis_obj = redis.Redis(host='0.0.0.0', port=12345)
    redis_obj = redis.ConnectionPool(host="0.0.0.0", port=12345, db=0)

    p = mp.Process(target=run_method, args=(redis_obj,))
    p.start()
    return 'OK'

if __name__ == "__main__":
    print(run())

Traceback (most recent call last):
  File "/Users/jackhart/Documents/pythonProject/main.py", line 33, in <module>
    print(run())
  File "/Users/jackhart/Documents/pythonProject/main.py", line 28, in run
    p.start()
  File "/usr/local/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/process.py", line 121, in start
    self._popen = self._Popen(self)
  File "/usr/local/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/context.py", line 224, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "/usr/local/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/context.py", line 284, in _Popen
    return Popen(process_obj)
  File "/usr/local/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/popen_spawn_posix.py", line 32, in __init__
    super().__init__(process_obj)
  File "/usr/local/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/popen_fork.py", line 19, in __init__
    self._launch(process_obj)
  File "/usr/local/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/popen_spawn_posix.py", line 47, in _launch
    reduction.dump(process_obj, fp)
  File "/usr/local/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
TypeError: cannot pickle '_thread.lock' object

[dustMason]

duplicate of https://github.com/redis/redis-py/issues/1029

[chayim]

Based on my reading this appears closed. Mind re-opening if you feel that this is incorrect?