Coverage for python/lsst/daf/butler/_utilities/named_locks.py: 38%

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1# This file is part of daf_butler. 

2# 

3# Developed for the LSST Data Management System. 

4# This product includes software developed by the LSST Project 

5# (http://www.lsst.org). 

6# See the COPYRIGHT file at the top-level directory of this distribution 

7# for details of code ownership. 

8# 

9# This software is dual licensed under the GNU General Public License and also 

10# under a 3-clause BSD license. Recipients may choose which of these licenses 

11# to use; please see the files gpl-3.0.txt and/or bsd_license.txt, 

12# respectively. If you choose the GPL option then the following text applies 

13# (but note that there is still no warranty even if you opt for BSD instead): 

14# 

15# This program is free software: you can redistribute it and/or modify 

16# it under the terms of the GNU General Public License as published by 

17# the Free Software Foundation, either version 3 of the License, or 

18# (at your option) any later version. 

19# 

20# This program is distributed in the hope that it will be useful, 

21# but WITHOUT ANY WARRANTY; without even the implied warranty of 

22# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

23# GNU General Public License for more details. 

24# 

25# You should have received a copy of the GNU General Public License 

26# along with this program. If not, see <http://www.gnu.org/licenses/>. 

27 

28from collections.abc import Iterator 

29from contextlib import contextmanager 

30from threading import Lock 

31 

32 

33class NamedLocks: 

34 """Maintains a collection of separate mutex locks, indexed by name.""" 

35 

36 def __init__(self) -> None: 

37 self._lookup_lock = Lock() 

38 self._named_locks = dict[str, Lock]() 

39 

40 @contextmanager 

41 def lock(self, name: str) -> Iterator[None]: 

42 """Return a context manager that acquires a mutex lock when entered and 

43 releases it when exited. 

44 

45 Parameters 

46 ---------- 

47 name : `str` 

48 The name of the lock. A separate lock instance is created for each 

49 distinct name. 

50 """ 

51 with self._get_lock(name): 

52 yield 

53 

54 def _get_lock(self, name: str) -> Lock: 

55 with self._lookup_lock: 

56 lock = self._named_locks.get(name, None) 

57 if lock is None: 

58 lock = Lock() 

59 self._named_locks[name] = lock 

60 

61 return lock