/django/contrib/sessions/backends/cache.py
Python | 58 lines | 42 code | 8 blank | 8 comment | 11 complexity | 5db4298ec1cc81a295709bb607e40f21 MD5 | raw file
Possible License(s): BSD-3-Clause
- 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)