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bpo-38501: Add a warning section to multiprocessing.Pool docs about resource managing (GH-19466)

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Pablo Galindo 2020-04-11 03:05:37 +01:00 committed by GitHub
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Doc/library/multiprocessing.rst
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@ -439,7 +439,8 @@ process which created it.
>>> def f(x): >>> def f(x):
... return x*x ... return x*x
... ...
>>> p.map(f, [1,2,3]) >>> with p:
... p.map(f, [1,2,3])
Process PoolWorker-1: Process PoolWorker-1:
Process PoolWorker-2: Process PoolWorker-2:
Process PoolWorker-3: Process PoolWorker-3:
@ -2127,6 +2128,16 @@ with the :class:`Pool` class.
Note that the methods of the pool object should only be called by Note that the methods of the pool object should only be called by
the process which created the pool. the process which created the pool.
.. warning::
:class:`multiprocessing.pool` objects have internal resources that need to be
properly managed (like any other resource) by using the pool as a context manager
or by calling :meth:`close` and :meth:`terminate` manually. Failure to do this
can lead to the process hanging on finalization.
Note that is **not correct** to rely on the garbage colletor to destroy the pool
as CPython does not assure that the finalizer of the pool will be called
(see :meth:`object.__del__` for more information).
.. versionadded:: 3.2 .. versionadded:: 3.2
*maxtasksperchild* *maxtasksperchild*