vishnu 1.0.2

Sessions for the Google App Engine Python runtime

Features

• Cookie based session for Google App Engine using the NDB datastore

• Configurable for the following cookie settings

  • Domain

  • Path

  • Secure

  • HttpOnly

  • Expires (timeout)

• 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

Configuration

app.yaml

Vishnu will automatically look for and use the following variables from your app.yaml config.

Name	Required	Default	Description
VISHNU_COOKIE_NAME	no	vishnu	The name to use for the cookie. If omitted it omitted it will default vishnu
VISHNU_SECRET	yes	N/A	Secret used for HMAC signature
VISHNU_ENCRYPT_KEY	no	N/A	Key used to encrypt cookie data, it omitted then value will not be encrypted.
VISHNU_DOMAIN	no	N/A	The domain to set the cookie for. If omitted it will default to the domain the cookie was served from.
VISHNU_PATH	no	/	The path to set the cookie for. If omitted it will default to /.
VISHNU_SECURE	no	true	Only send this cookie over SSL.
VISHNU_HTTP_ONLY	no	true	Only allow cookie access via HTTP/HTTPS.
VISHNU_AUTO_SAVE	no	false	Automatically save the session when a value is set.
VISHNU_TIMEOUT	no	N/A	How long until this cookie expires. If omitted it will last for the length of the browser session.

Dependencies

If using encryption you will need to add the following to your app.yaml.

libraries:
- name: pycrypto
  version: "2.6"

WSGI Middleware

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

from vishnu.middleware import SessionMiddleware
app = SessionMiddleware(app)

Setting a Custom Timeout

Each session uses the default timeout specified in app.yaml 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

Add the following to a cron handler.

import vishnu

while not vishnu.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.