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"""
Caching framework.
This package defines set of cache backends that all conform to a simple API.
In a nutshell, a cache is a set of values -- which can be any object that
may be pickled -- identified by string keys. For the complete API, see
the abstract BaseCache class in django.core.cache.backends.base.
Client code should use the `cache` variable defined here to access the default
cache backend and look up non-default cache backends in the `caches` dict-like
object.
See docs/topics/cache.txt for information on the public API.
"""
from threading import local
from django.conf import settings
from django.core import signals
from django.core.cache.backends.base import (
InvalidCacheBackendError, CacheKeyWarning, BaseCache)
from django.core.exceptions import ImproperlyConfigured
from django.utils.module_loading import import_string
__all__ = [
'cache', 'DEFAULT_CACHE_ALIAS', 'InvalidCacheBackendError',
'CacheKeyWarning', 'BaseCache',
]
DEFAULT_CACHE_ALIAS = 'default'
if DEFAULT_CACHE_ALIAS not in settings.CACHES:
raise ImproperlyConfigured("You must define a '%s' cache" % DEFAULT_CACHE_ALIAS)
def _create_cache(backend, **kwargs):
try:
# Try to get the CACHES entry for the given backend name first
try:
conf = settings.CACHES[backend]
except KeyError:
try:
# Trying to import the given backend, in case it's a dotted path
import_string(backend)
except ImportError as e:
raise InvalidCacheBackendError("Could not find backend '%s': %s" % (
backend, e))
location = kwargs.pop('LOCATION', '')
params = kwargs
else:
params = conf.copy()
params.update(kwargs)
backend = params.pop('BACKEND')
location = params.pop('LOCATION', '')
backend_cls = import_string(backend)
except ImportError as e:
raise InvalidCacheBackendError(
"Could not find backend '%s': %s" % (backend, e))
return backend_cls(location, params)
class CacheHandler(object):
"""
A Cache Handler to manage access to Cache instances.
Ensures only one instance of each alias exists per thread.
"""
def __init__(self):
self._caches = local()
def __getitem__(self, alias):
try:
return self._caches.caches[alias]
except AttributeError:
self._caches.caches = {}
except KeyError:
pass
if alias not in settings.CACHES:
raise InvalidCacheBackendError(
"Could not find config for '%s' in settings.CACHES" % alias
)
cache = _create_cache(alias)
self._caches.caches[alias] = cache
return cache
def all(self):
return getattr(self._caches, 'caches', {}).values()
caches = CacheHandler()
class DefaultCacheProxy(object):
"""
Proxy access to the default Cache object's attributes.
This allows the legacy `cache` object to be thread-safe using the new
``caches`` API.
"""
def __getattr__(self, name):
return getattr(caches[DEFAULT_CACHE_ALIAS], name)
def __setattr__(self, name, value):
return setattr(caches[DEFAULT_CACHE_ALIAS], name, value)
def __delattr__(self, name):
return delattr(caches[DEFAULT_CACHE_ALIAS], name)
def __contains__(self, key):
return key in caches[DEFAULT_CACHE_ALIAS]
def __eq__(self, other):
return caches[DEFAULT_CACHE_ALIAS] == other
def __ne__(self, other):
return caches[DEFAULT_CACHE_ALIAS] != other
cache = DefaultCacheProxy()
def close_caches(**kwargs):
# Some caches -- python-memcached in particular -- need to do a cleanup at the
# end of a request cycle. If not implemented in a particular backend
# cache.close is a no-op
for cache in caches.all():
cache.close()
signals.request_finished.connect(close_caches)
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