- Author:
- dipankarsarkar
- Posted:
- November 15, 2008
- Language:
- Python
- Version:
- 1.0
- Score:
- 0 (after 0 ratings)
This solves the problem of losing sessions data when you restart memcached. So you use a different memcached instance for sessions which you rarely restart.
Use the above code and add the following to you settings.py
SESSION_ENGINE = "kwippyproject.session_backend"
SESSION_CACHE = 'memcached://127.0.0.1:11200/'
(Above assumes that your session's memcached is running on port 11200)
Feel free to contact me in case you need help. By Dipankar sarkar [email protected]
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 | <project>/session_backend.py
from django.contrib.sessions.backends.base import SessionBase, CreateError
from kwippyproject.session_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)
----------------------
<project>/session_cache.py
from django.core.cache.backends.memcached import CacheClass
from django.conf import settings
scheme, rest = settings.SESSION_CACHE.split(':', 1)
host = rest[2:-1]
cache = CacheClass(host,{})
|
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