vishnu

Disclaimer: Cookies are largely obsolete. For newer application consider using technologies like JWT which will also eliminate the need for shared backends for session storage. We have moved all our projects to use JWT and the likes and are no longer maintaining this project.

Sessions for python WSGI applications.

Features

• Cookie based session for python WSGI applications

• Configurable for the following cookie settings

  • Domain
  • Path
  • Secure
  • HttpOnly
  • Expires (timeout)

• Support for multiple backends

  • Google App Engine Memcache
  • Google App Engine NDB
  • Google Cloud Datastore
  • Python Memcached
  • PyMemcache
  • Redis

• HMAC signature to verify cookie has not been tampered with
• Autosave option which saves anytime a session value is modified
• Optional Encryption of cookie data using AES
• Custom timeout per session

Installation

Vishnu is available on PyPi and we recommend installation via pip.

pip install vishnu

The following extra installations also exist which include the desired backend library as a requirement.

pip install vishnu[pymemcache]
pip install vishnu[python-memcached]
pip install vishnu[redis]
pip install vishnu[datastore]

If you are working with Google App Engine we recommend installation via pip as a vendored package.

pip install -t lib vishnu

Edit the appengine_config.py file and provide your library directory to the vendor.add() method.

from google.appengine.ext import vendor

vendor.add('lib')

Alternatively download your preferred tagged release and all you should have to include is the vishnu folder.

Configuration

Session Config

The following parameters are available for session configuration.

Example of a session configuration.

from vishnu.session import Config
from vishnu.backend import Redis

config = Config(
    secret="your_secret",
    backend=Redis()
)

WSGI Middleware

To use vishnu you must add it as a middleware to your WSGI application.

from vishnu.backend import Redis
from vishnu.middleware import SessionMiddleware
from vishnu.session import Config


my_config = Config(
    secret="your_secret",
    backend=Redis()
)

app = SessionMiddleware(app=wsgi_app, config=my_config)

Backends

Google App Engine (memcache)

from vishnu.backend import GoogleAppEngineMemcache

config = Config(
    secret="your_secret",
    backend=GoogleAppEngineMemcache()
)

Google App Engine (NDB)

from vishnu.backend import GoogleAppEngineNDB

config = Config(
    secret="your_secret",
    backend=GoogleAppEngineNDB()
)

PyMemcache

from vishnu.backend import PyMemcache

config = Config(
    secret="your_secret",
    backend=PyMemcache(host="memcache.host", port=11222)
)

PythonMemcached

from vishnu.backend import PythonMemcached

config = Config(
    secret="your_secret",
    backend=PythonMemcached()
)

Redis

from vishnu.backend import Redis

config = Config(
    secret="your_secret",
    backend=Redis(host="redis.host", port=6421, db=0)
)

Setting a Custom Timeout

Each session uses the default timeout specified in your server config but if you want to have particular sessions differ to this you can do the following.

session = vishnu.get_session()
session.timeout = 3600
session.save()

The timeout is in seconds. To set the timeout to expire at the end of this session you can use the vishnu.session.TIMEOUT_SESSION constant.

session = vishnu.get_session()
session.timeout = vishnu.session.TIMEOUT_SESSION
session.save()

Cleaning up Expired Sessions (Google App Engine NDB backend only)

Add the following to a cron handler.

from vishnu.util import gae_ndb_delete_expired_sessions

while not gae_ndb_delete_expired_sessions():
    pass

You can alter the period after expired sessions are deleted by passing a value in seconds as dormant_for. You can also alter the amount of sessions to delete per call using the limit argument.

from vishnu.util import gae_ndb_delete_expired_sessions

while not gae_ndb_delete_expired_sessions(dormant_for=3600, limit=100):
    pass