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| author | Paul Ganssle <paul@ganssle.io> | 2019-11-02 21:24:29 -0400 |
|---|---|---|
| committer | Paul Ganssle <paul@ganssle.io> | 2019-11-02 21:33:04 -0400 |
| commit | 6e92f2111589ab061b66bd332dcb4a33a58acb84 (patch) | |
| tree | 2d39ee4522ab4ae5d8acd6602869968abb8ed950 | |
| parent | 2e36ff7e48da1ee248881bbba361a5f2538cfa90 (diff) | |
| download | dateutil-git-6e92f2111589ab061b66bd332dcb4a33a58acb84.tar.gz | |
Lock around strong cache updates
Since the strong cache uses operations in OrderedDict that are not
thread-safe in Python 2, it is necessary to acquire a lock while
updating the dictionary.
When Python 2 support is dropped, we can likely refactor this to avoid
locking.
| -rw-r--r-- | changelog.d/973.bugfix.rst | 1 | ||||
| -rw-r--r-- | dateutil/tz/_factories.py | 29 |
2 files changed, 19 insertions, 11 deletions
diff --git a/changelog.d/973.bugfix.rst b/changelog.d/973.bugfix.rst new file mode 100644 index 0000000..6af867c --- /dev/null +++ b/changelog.d/973.bugfix.rst @@ -0,0 +1 @@ +Fixed a race condition in the ``tzoffset`` and ``tzstr`` "strong" caches on Python 2.7. Reported by @kainjow (gh issue #901). diff --git a/dateutil/tz/_factories.py b/dateutil/tz/_factories.py index d2560eb..f8a6589 100644 --- a/dateutil/tz/_factories.py +++ b/dateutil/tz/_factories.py @@ -2,6 +2,8 @@ from datetime import timedelta import weakref from collections import OrderedDict +from six.moves import _thread + class _TzSingleton(type): def __init__(cls, *args, **kwargs): @@ -26,6 +28,8 @@ class _TzOffsetFactory(_TzFactory): cls.__strong_cache = OrderedDict() cls.__strong_cache_size = 8 + cls._cache_lock = _thread.allocate_lock() + def __call__(cls, name, offset): if isinstance(offset, timedelta): key = (name, offset.total_seconds()) @@ -37,12 +41,13 @@ class _TzOffsetFactory(_TzFactory): instance = cls.__instances.setdefault(key, cls.instance(name, offset)) - cls.__strong_cache[key] = cls.__strong_cache.pop(key, instance) + # This lock may not be necessary in Python 3. See GH issue #901 + with cls._cache_lock: + cls.__strong_cache[key] = cls.__strong_cache.pop(key, instance) - # Remove an item if the strong cache is overpopulated - # TODO: Maybe this should be under a lock? - if len(cls.__strong_cache) > cls.__strong_cache_size: - cls.__strong_cache.popitem(last=False) + # Remove an item if the strong cache is overpopulated + if len(cls.__strong_cache) > cls.__strong_cache_size: + cls.__strong_cache.popitem(last=False) return instance @@ -53,6 +58,8 @@ class _TzStrFactory(_TzFactory): cls.__strong_cache = OrderedDict() cls.__strong_cache_size = 8 + cls.__cache_lock = _thread.allocate_lock() + def __call__(cls, s, posix_offset=False): key = (s, posix_offset) instance = cls.__instances.get(key, None) @@ -61,13 +68,13 @@ class _TzStrFactory(_TzFactory): instance = cls.__instances.setdefault(key, cls.instance(s, posix_offset)) - cls.__strong_cache[key] = cls.__strong_cache.pop(key, instance) - + # This lock may not be necessary in Python 3. See GH issue #901 + with cls.__cache_lock: + cls.__strong_cache[key] = cls.__strong_cache.pop(key, instance) - # Remove an item if the strong cache is overpopulated - # TODO: Maybe this should be under a lock? - if len(cls.__strong_cache) > cls.__strong_cache_size: - cls.__strong_cache.popitem(last=False) + # Remove an item if the strong cache is overpopulated + if len(cls.__strong_cache) > cls.__strong_cache_size: + cls.__strong_cache.popitem(last=False) return instance |