"""
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 not access a cache backend directly; instead it should
either use the "cache" variable made available here, or it should use the
get_cache() function made available here. get_cache() takes a backend URI
(e.g. "memcached://127.0.0.1:11211/") and returns an instance of a backend
cache class.
See docs/cache.txt for information on the public API.
"""
from cgi import parse_qsl
from django.conf import settings
from django.core import signals
from django.core.cache.backends.base import InvalidCacheBackendError
from django.utils import importlib
# Name for use in settings file --> name of module in "backends" directory.
# Any backend scheme that is not in this dictionary is treated as a Python
# import path to a custom backend.
BACKENDS = {
'memcached': 'memcached',
'locmem': 'locmem',
'file': 'filebased',
'db': 'db',
'dummy': 'dummy',
}
def parse_backend_uri(backend_uri):
"""
Converts the "backend_uri" into a cache scheme ('db', 'memcached', etc), a
host and any extra params that are required for the backend. Returns a
(scheme, host, params) tuple.
"""
if backend_uri.find(':') == -1:
raise InvalidCacheBackendError("Backend URI must start with scheme://")
scheme, rest = backend_uri.split(':', 1)
if not rest.startswith('//'):
raise InvalidCacheBackendError("Backend URI must start with scheme://")
host = rest[2:]
qpos = rest.find('?')
if qpos != -1:
params = dict(parse_qsl(rest[qpos+1:]))
host = rest[2:qpos]
else:
params = {}
if host.endswith('/'):
host = host[:-1]
return scheme, host, params
def get_cache(backend_uri):
scheme, host, params = parse_backend_uri(backend_uri)
if scheme in BACKENDS:
name = 'django.core.cache.backends.%s' % BACKENDS[scheme]
else:
name = scheme
module = importlib.import_module(name)
return getattr(module, 'CacheClass')(host, params)
cache = get_cache(settings.CACHE_BACKEND)
# Some caches -- pythont-memcached in particular -- need to do a cleanup at the
# end of a request cycle. If the cache provides a close() method, wire it up
# here.
if hasattr(cache, 'close'):
signals.request_finished.connect(cache.close)
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