app/django/contrib/sessions/backends/cache.py
author Todd Larsen <tlarsen@google.com>
Tue, 14 Oct 2008 21:39:57 +0000
changeset 329 2d90d49ce78a
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Add is_featured boolean property to the Work model, so that Works can be designated as "featured" items in various places in the UI. This will be used to allow Sponsors, Programs, and Organizations to select Documents that should be included in their sidebar menus. Perhaps featured "site" Documents, such as site-wide Terms of Service, should probably be listed below the "User (sign-out)" menu, since the User will have to read and agree to these before being allowed to use the site. A collapsable Javascript sidebar is probably going to be needed soon... Patch by: Todd Larsen Review 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)