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"""
Cached, database-backed sessions.
"""
from django.conf import settings
from django.contrib.sessions.backends.db import SessionStore as DBStore
from django.core.cache import caches
KEY_PREFIX = "django.contrib.sessions.cached_db"
class SessionStore(DBStore):
"""
Implement cached, database backed sessions.
"""
cache_key_prefix = KEY_PREFIX
def __init__(self, session_key=None):
self._cache = caches[settings.SESSION_CACHE_ALIAS]
super().__init__(session_key)
@property
def cache_key(self):
return self.cache_key_prefix + self._get_or_create_session_key()
def load(self):
try:
data = self._cache.get(self.cache_key)
except Exception:
# Some backends (e.g. memcache) raise an exception on invalid
# cache keys. If this happens, reset the session. See #17810.
data = None
if data is None:
s = self._get_session_from_db()
if s:
data = self.decode(s.session_data)
self._cache.set(self.cache_key, data, self.get_expiry_age(expiry=s.expire_date))
else:
data = {}
return data
def exists(self, session_key):
return session_key and (self.cache_key_prefix + session_key) in self._cache or super().exists(session_key)
def save(self, must_create=False):
super().save(must_create)
self._cache.set(self.cache_key, self._session, self.get_expiry_age())
def delete(self, session_key=None):
super().delete(session_key)
if session_key is None:
if self.session_key is None:
return
session_key = self.session_key
self._cache.delete(self.cache_key_prefix + session_key)
def flush(self):
"""
Remove the current session data from the database and regenerate the
key.
"""
self.clear()
self.delete(self.session_key)
self._session_key = None