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Code Issues 25 Releases Wiki Activity

Fixed #26332 -- Fixed a race condition in BaseCache.get_or_set().

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This commit is contained in:
Przemysław Suliga 2016-03-06 11:34:23 +01:00 committed by Tim Graham
parent b4250ea04a
commit 96ec67a7cf
3 changed files with 17 additions and 6 deletions
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10
django/core/cache/backends/base.py vendored
View File

@ -154,8 +154,7 @@ class BaseCache(object):
also be any callable. If timeout is given, that timeout will be used also be any callable. If timeout is given, that timeout will be used
for the key; otherwise the default cache timeout will be used. for the key; otherwise the default cache timeout will be used.
Returns the value of the key stored or retrieved on success, Return the value of the key stored or retrieved.
False on error.
""" """
if default is None: if default is None:
raise ValueError('You need to specify a value.') raise ValueError('You need to specify a value.')
@ -163,9 +162,10 @@ class BaseCache(object):
if val is None: if val is None:
if callable(default): if callable(default):
default = default() default = default()
val = self.add(key, default, timeout=timeout, version=version) self.add(key, default, timeout=timeout, version=version)
if val: # Fetch the value again to avoid a race condition if another caller
return self.get(key, default, version) # added a value between the first get() and the add() above.
return self.get(key, default, version=version)
return val return val
def has_key(self, key, version=None): def has_key(self, key, version=None):

4
docs/releases/1.9.5.txt
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@ -12,3 +12,7 @@ Bugfixes
* Made ``MultiPartParser`` ignore filenames that normalize to an empty string * Made ``MultiPartParser`` ignore filenames that normalize to an empty string
to fix crash in ``MemoryFileUploadHandler`` on specially crafted user input to fix crash in ``MemoryFileUploadHandler`` on specially crafted user input
(:ticket:`26325`). (:ticket:`26325`).
* Fixed a race condition in ``BaseCache.get_or_set()`` (:ticket:`26332`). It
now returns the ``default`` value instead of ``False`` if there's an error
when trying to add the value to the cache.

9
tests/cache/tests.py vendored
View File

@ -30,7 +30,7 @@ from django.template import engines
from django.template.context_processors import csrf from django.template.context_processors import csrf
from django.template.response import TemplateResponse from django.template.response import TemplateResponse
from django.test import ( from django.test import (
RequestFactory, SimpleTestCase, TestCase, TransactionTestCase, RequestFactory, SimpleTestCase, TestCase, TransactionTestCase, mock,
override_settings, override_settings,
) )
from django.test.signals import setting_changed from django.test.signals import setting_changed
@ -931,6 +931,13 @@ class BaseCacheTests(object):
self.assertEqual(cache.get_or_set('brian', 1979, version=2), 1979) self.assertEqual(cache.get_or_set('brian', 1979, version=2), 1979)
self.assertIsNone(cache.get('brian', version=3)) self.assertIsNone(cache.get('brian', version=3))
def test_get_or_set_racing(self):
with mock.patch('%s.%s' % (settings.CACHES['default']['BACKEND'], 'add')) as cache_add:
# Simulate cache.add() failing to add a value. In that case, the
# default value should be returned.
cache_add.return_value = False
self.assertEqual(cache.get_or_set('key', 'default'), 'default')
@override_settings(CACHES=caches_setting_for_tests( @override_settings(CACHES=caches_setting_for_tests(
BACKEND='django.core.cache.backends.db.DatabaseCache', BACKEND='django.core.cache.backends.db.DatabaseCache',