A redis backend for Django Sessions, tested on Django 1.3+

redis_session_backend.py

from django.contrib.sessions.backends.base import SessionBase, CreateError
from django.conf import settings
from django.utils.encoding import force_unicode
import redis

class SessionStore(SessionBase):
    """ Redis store for sessions"""

    def __init__(self, session_key=None):
        self.redis = redis.Redis(
            host = settings.SESSION_REDIS_HOST,
            port = settings.SESSION_REDIS_PORT,
            socket_timeout = settings.REDIS_SOCKET_TIMEOUT
        )
        super(SessionStore, self).__init__(session_key)

    @classmethod
    def _get_key_for_redis(self, session_key):
        return 'sessionstore:%s' % session_key

    def _redis_key(self):
        return self.__class__._get_key_for_redis(self.session_key)

    def load(self):
        session_data = self.redis.get(self._redis_key())
        if session_data is not None:
            return self.decode(force_unicode(session_data))
        else:
            self.create()
            return {}

    def create(self):
        max_attempts = 10
        attempt = 0
        while True:
            self.session_key = self._get_new_session_key()
            session_dict = self._get_session(no_load = True)
            session_data = self.encode(session_dict)

            was_created = self.redis.setnx(self._redis_key(), 
                                           session_data)
            if was_created:
                self.redis.expire(self._redis_key(),
                                  settings.SESSION_COOKIE_AGE)
                self.modified = True
                self._session_cache = session_dict
                return
            else:
                # extremely unlikely
                if attempt == max_attempts:
                    raise CreateError
                else:
                    attempt += 1
                    continue

    def save(self, must_create=False):
        if must_create:
            self.create()
        else:
            encoded_data = self.encode(self._session)
            self.redis.setex(self._redis_key(), encoded_data, settings.SESSION_COOKIE_AGE)

    def exists(self, session_key):
        return self.redis.exists(self.__class__._get_key_for_redis(session_key))

    def delete(self, session_key=None):
        to_delete = (session_key or self.session_key)
        redis_key = self.__class__._get_key_for_redis(to_delete)
        self.redis.delete(redis_key)

Hello Mike,

I am testing your session backend but I am receiving the following error:

AttributeError at /directlogin/
can't set attribute

You have idea what can cause this?

Best Regards

We are testing your backend for session data, with the intent of using multiple redis servers in a replicated environment. Any hints would be appreciated.

you should get the below block out from the class's init to avoid calling it every time it is instantiated...to be called only one time.

self.redis = redis.Redis(
host = settings.SESSION_REDIS_HOST,
port = settings.SESSION_REDIS_PORT,
socket_timeout = settings.REDIS_SOCKET_TIMEOUT
)

I think he wants a socket or each instance he creates, not to share sockets between all instances. That's why it is self.redis is assigned in the init func.