54 lines
1.9 KiB
Python
54 lines
1.9 KiB
Python
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"""Helper module to factorize the conditional multiprocessing import logic
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We use a distinct module to simplify import statements and avoid introducing
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circular dependencies (for instance for the assert_spawning name).
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"""
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import os
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import warnings
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# Obtain possible configuration from the environment, assuming 1 (on)
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# by default, upon 0 set to None. Should instructively fail if some non
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# 0/1 value is set.
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mp = int(os.environ.get('JOBLIB_MULTIPROCESSING', 1)) or None
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if mp:
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try:
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import multiprocessing as mp
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import _multiprocessing # noqa
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except ImportError:
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mp = None
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# 2nd stage: validate that locking is available on the system and
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# issue a warning if not
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if mp is not None:
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try:
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# try to create a named semaphore using SemLock to make sure they are
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# available on this platform. We use the low level object
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# _multiprocessing.SemLock to avoid spawning a resource tracker on
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# Unix system or changing the default backend.
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import tempfile
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from _multiprocessing import SemLock
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_rand = tempfile._RandomNameSequence()
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for i in range(100):
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try:
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name = '/joblib-{}-{}' .format(
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os.getpid(), next(_rand))
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_sem = SemLock(0, 0, 1, name=name, unlink=True)
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del _sem # cleanup
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break
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except FileExistsError as e: # pragma: no cover
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if i >= 99:
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raise FileExistsError(
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'cannot find name for semaphore') from e
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except (FileExistsError, AttributeError, ImportError, OSError) as e:
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mp = None
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warnings.warn('%s. joblib will operate in serial mode' % (e,))
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# 3rd stage: backward compat for the assert_spawning helper
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if mp is not None:
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from multiprocessing.context import assert_spawning
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else:
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assert_spawning = None
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