app/django/contrib/sessions/backends/cache.py
author Lennard de Rijk <ljvderijk@gmail.com>
Fri, 23 Jan 2009 09:08:26 +0000
changeset 913 db38e7680d1c
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Added state property to role model. This can be used when for instance a member has been removed from a club or a when a program has been marked inactive. Certain roles would then be shown on the upcoming roles page marked as previous roles. This would give us the archiving capability that was shown in the mockup. Patch by: Lennard de Rijk Reviewd by: to-be-reviewed

from django.contrib.sessions.backends.base import SessionBase, CreateError
from django.core.cache import 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(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(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.get(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(session_key)