Simple App Engine Sessions Implementation
- by raz0r
Here is a very basic class for handling sessions on App Engine:
"""Lightweight implementation of cookie-based sessions for Google App Engine.
Classes:
Session
"""
import os
import random
import Cookie
from google.appengine.api import memcache
_COOKIE_NAME = 'app-sid'
_COOKIE_PATH = '/'
_SESSION_EXPIRE_TIME = 180 * 60
class Session(object):
"""Cookie-based session implementation using Memcached."""
def __init__(self):
self.sid = None
self.key = None
self.session = None
cookie_str = os.environ.get('HTTP_COOKIE', '')
self.cookie = Cookie.SimpleCookie()
self.cookie.load(cookie_str)
if self.cookie.get(_COOKIE_NAME):
self.sid = self.cookie[_COOKIE_NAME].value
self.key = 'session-' + self.sid
self.session = memcache.get(self.key)
if self.session:
self._update_memcache()
else:
self.sid = str(random.random())[5:] + str(random.random())[5:]
self.key = 'session-' + self.sid
self.session = dict()
memcache.add(self.key, self.session, _SESSION_EXPIRE_TIME)
self.cookie[_COOKIE_NAME] = self.sid
self.cookie[_COOKIE_NAME]['path'] = _COOKIE_PATH
print self.cookie
def __len__(self):
return len(self.session)
def __getitem__(self, key):
if key in self.session:
return self.session[key]
raise KeyError(str(key))
def __setitem__(self, key, value):
self.session[key] = value
self._update_memcache()
def __delitem__(self, key):
if key in self.session:
del self.session[key]
self._update_memcache()
return None
raise KeyError(str(key))
def __contains__(self, item):
try:
i = self.__getitem__(item)
except KeyError:
return False
return True
def _update_memcache(self):
memcache.replace(self.key, self.session, _SESSION_EXPIRE_TIME)
I would like some advices on how to improve the code for better security.
Note: In the production version it will also save a copy of the session in the datastore.
Note': I know there are much more complete implementations available online though I would like to learn more about this subject so please don't answer the question with "use that" or "use the other" library.
