app/django/contrib/sessions/backends/cache.py
author Pawel Solyga <Pawel.Solyga@gmail.com>
Mon, 01 Jun 2009 22:23:46 +0200
changeset 2376 feec28b50f1b
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Extend taggable-mixin to support different Tag models. Usage is pretty simple. Tag model is default in Taggable constructor but you can call it with different model like GHOPTaskType that inherits from Tag model. Both Taggable and Tag models have been updated and they don't use hardcoded Tag model anymore and instead use cls of class methods or self.__class__. In case of Taggable it's self.__tag_model.

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)