Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/joblib/_multiprocessing_helpers.py: 77%

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""" 

6import os 

7import warnings 

8 

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 as mp 

17 import _multiprocessing # noqa 

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( 

36 os.getpid(), next(_rand)) 

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

38 del _sem # cleanup 

39 break 

40 except FileExistsError as e: # pragma: no cover 

41 if i >= 99: 

42 raise FileExistsError( 

43 'cannot find name for semaphore') from e 

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

45 mp = None 

46 warnings.warn('%s. joblib will operate in serial mode' % (e,)) 

47 

48 

49# 3rd stage: backward compat for the assert_spawning helper 

50if mp is not None: 

51 from multiprocessing.context import assert_spawning 

52else: 

53 assert_spawning = None