82 lines
2.6 KiB
Python
82 lines
2.6 KiB
Python
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from django.conf import settings
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from django.contrib.sessions.backends.base import (
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CreateError, SessionBase, UpdateError,
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)
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from django.core.cache import caches
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KEY_PREFIX = "django.contrib.sessions.cache"
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class SessionStore(SessionBase):
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"""
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A cache-based session store.
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"""
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cache_key_prefix = KEY_PREFIX
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def __init__(self, session_key=None):
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self._cache = caches[settings.SESSION_CACHE_ALIAS]
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super().__init__(session_key)
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@property
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def cache_key(self):
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return self.cache_key_prefix + self._get_or_create_session_key()
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def load(self):
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try:
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session_data = self._cache.get(self.cache_key)
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except Exception:
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# Some backends (e.g. memcache) raise an exception on invalid
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# cache keys. If this happens, reset the session. See #17810.
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session_data = None
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if session_data is not None:
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return session_data
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self._session_key = None
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return {}
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def create(self):
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# Because a cache can fail silently (e.g. memcache), we don't know if
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# we are failing to create a new session because of a key collision or
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# because the cache is missing. So we try for a (large) number of times
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# and then raise an exception. That's the risk you shoulder if using
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# cache backing.
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for i in range(10000):
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self._session_key = self._get_new_session_key()
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try:
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self.save(must_create=True)
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except CreateError:
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continue
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self.modified = True
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return
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raise RuntimeError(
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"Unable to create a new session key. "
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"It is likely that the cache is unavailable.")
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def save(self, must_create=False):
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if self.session_key is None:
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return self.create()
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if must_create:
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func = self._cache.add
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elif self._cache.get(self.cache_key) is not None:
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func = self._cache.set
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else:
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raise UpdateError
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result = func(self.cache_key,
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self._get_session(no_load=must_create),
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self.get_expiry_age())
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if must_create and not result:
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raise CreateError
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def exists(self, session_key):
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return bool(session_key) and (self.cache_key_prefix + session_key) in self._cache
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def delete(self, session_key=None):
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if session_key is None:
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if self.session_key is None:
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return
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session_key = self.session_key
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self._cache.delete(self.cache_key_prefix + session_key)
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@classmethod
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def clear_expired(cls):
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pass
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