Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.11/site-packages/joblib/_multiprocessing_helpers.py: 78%

1"""Helper module to factorize the conditional multiprocessing import logic 

2 

3We use a distinct module to simplify import statements and avoid introducing 

4circular dependencies (for instance for the assert_spawning name). 

5""" 

6 

7import os 

8import warnings 

9 

10# Obtain possible configuration from the environment, assuming 1 (on) 

11# by default, upon 0 set to None. Should instructively fail if some non 

12# 0/1 value is set. 

13mp = int(os.environ.get("JOBLIB_MULTIPROCESSING", 1)) or None 

14if mp: 

15 try: 

16 import _multiprocessing # noqa 

17 import multiprocessing as mp 

18 except ImportError: 

19 mp = None 

20 

21# 2nd stage: validate that locking is available on the system and 

22# issue a warning if not 

23if mp is not None: 

24 try: 

25 # try to create a named semaphore using SemLock to make sure they are 

26 # available on this platform. We use the low level object 

27 # _multiprocessing.SemLock to avoid spawning a resource tracker on 

28 # Unix system or changing the default backend. 

29 import tempfile 

30 from _multiprocessing import SemLock 

31 

32 _rand = tempfile._RandomNameSequence() 

33 for i in range(100): 

34 try: 

35 name = "/joblib-{}-{}".format(os.getpid(), next(_rand)) 

36 _sem = SemLock(0, 0, 1, name=name, unlink=True) 

37 del _sem # cleanup 

38 break 

39 except FileExistsError as e: # pragma: no cover 

40 if i >= 99: 

41 raise FileExistsError("cannot find name for semaphore") from e 

42 except (FileExistsError, AttributeError, ImportError, OSError) as e: 

43 mp = None 

44 warnings.warn("%s. joblib will operate in serial mode" % (e,)) 

45 

46 

47# 3rd stage: backward compat for the assert_spawning helper 

48if mp is not None: 

49 from multiprocessing.context import assert_spawning 

50else: 

51 assert_spawning = None