Tornado Sessions

Introduction

Tornado sessions is a basic system for handling session data stored in Redis. A secure cookie on the client stores the session id, which maps to a hash of pickled data in redis.

Handlers inheriting from SessionHandler or methods wrapped by @sessionare session aware, with a self.session object that can be accessed as a dict, which is saved on handler finish.

Requirements

• Tornado
• Redis

Usage

To use sessions, you must have a cookie secret set (for secure cookies).

There are two was to give handlers session access.

First using the @session wrapper on handler methods:

class MainHandler(tornado.web.RequestHandler):

    @session
    def get(self):
        self.session # this is loaded now

Alternatively, handlers inheriting from SessionHandler:

class MainHandler(SessionHandler):

    def get(self):
        self.session # this is loaded now

The self.session object can be treated as a dict that is automatically saved to Redis when the handler method finishes. For example:

class MainHandler(SessionHandler):

    def get(self):
        self.session['foo'] = 'bar'
        self.session['an_int'] = 7
        self.session['arbitrary_object'] = datetime.datetime.now()

class LaterHandler(SessionHandler):

    def get(self):
        foo = self.session['foo'] # bar
        last_access = self.session['arbitrary_object'] # datetime object
        self.session['not_set'] # raises KeyError
        # in general, either use get or try/except
        self.session.get('not_set') # None
        # pop also works
        self.session.pop('an_int')