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from django.contrib.sessions.backends.base import SessionBase, CreateError
from django.core.cache import cache
KEY_PREFIX = "django.contrib.sessions.cache"
class SessionStore(SessionBase):
"""
A cache-based session store.
"""
def __init__(self, session_key=None):
self._cache = cache
super(SessionStore, self).__init__(session_key)
def load(self):
session_data = self._cache.get(KEY_PREFIX + self.session_key)
if session_data is not None:
return session_data
self.create()
return {}
def create(self):
# Because a cache can fail silently (e.g. memcache), we don't know if
# we are failing to create a new session because of a key collision or
# because the cache is missing. So we try for a (large) number of times
# and then raise an exception. That's the risk you shoulder if using
# cache backing.
for i in xrange(10000):
self.session_key = self._get_new_session_key()
try:
self.save(must_create=True)
except CreateError:
continue
self.modified = True
return
raise RuntimeError("Unable to create a new session key.")
def save(self, must_create=False):
if must_create:
func = self._cache.add
else:
func = self._cache.set
result = func(KEY_PREFIX + self.session_key, self._get_session(no_load=must_create),
self.get_expiry_age())
if must_create and not result:
raise CreateError
def exists(self, session_key):
if self._cache.has_key(KEY_PREFIX + session_key):
return True
return False
def delete(self, session_key=None):
if session_key is None:
if self._session_key is None:
return
session_key = self._session_key
self._cache.delete(KEY_PREFIX + session_key)
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