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Provides a framwork for creating multiple adhoc session binds in Pyramid.

Project description

pyramid_session_multi

Build Status: Python package

Provides for making multiple ad-hoc binds of ISession compliant Sessions onto a request.session_multi namespace.

Usage

Include pyramid_session_multi, then register some ISessionFactory factories that are compliant with the ISession interface -- just like you would with Pyramid's built-in .session system.

from pyramid.session import SignedCookieSessionFactory

session_factory_a = SignedCookieSessionFactory(
	'secret', cookie_name='session_a'
)
session_factory_b = SignedCookieSessionFactory(
	'secret', cookie_name='session_b'
)

def main(global_config, **settings):
    config = Configurator(settings=settings)
    config.include('pyramid_session_multi')
    pyramid_session_multi.register_session_factory(
    	config, 'session1', session_factory_a
    )
    pyramid_session_multi.register_session_factory(
    	config, 'session2', session_factory_b
    )
    return config.make_wsgi_app()

Note: The second argument to pyramid_session_multi.register_session_factory is a namespace, which we then use to access Session data in views/etc:

request.session_multi['session1']['foo'] = "bar"
request.session_multi['session2']['bar'] = "foo"

pyramid_session_multi lazily evaluates each Session namespace independently of each other, so accessing request.session_multi will not instantiate any of the component Sessions.

pyramid_session_multi is completely independent of Pyramid's built-in Session support, so you can still use request.session alongside this library!

Advanced Usage

register_session_factory accepts an optional argument: "discriminator".

A "discriminator" is a callable function that will receive a single argument: the active request.

If the discriminator function returns True, the SessionFactory will be invoked and a Session object will be mounted onto the namespace.

If the discriminator function returns a non-True value (e.g. False or None), the SessionFactory will NOT be invoked, and None will be mounted onto the session's namespace.

Consider an application that is run on both http and https protocols. In the following example, .session_multi["weak"] can always be accessed, but .session_multi["https_only"] will only be available on https connections.

from pyramid.session import SignedCookieSessionFactory

session_factory_a = SignedCookieSessionFactory(
	'secret', cookie_name='weak_cookie'
)
session_factory_b = SignedCookieSessionFactory(
	'secret', cookie_name='secure_cookie', secure=True, httponly=True
)

def session_b_discriminator(request):
	if request.scheme == 'https'
		return True
	return False

def main(global_config, **settings):
    config = Configurator(settings=settings)
    config.include('pyramid_session_multi')
    pyramid_session_multi.register_session_factory(
    	config, 'weak', session_factory_a
    )
    pyramid_session_multi.register_session_factory(
    	config, 'https_only', session_factory_b, discriminator=session_b_discriminator
    )
    return config.make_wsgi_app()

With this discriminator in place, .session_multi["https_only"] will only be a Pyramid ISession on https connections; on http connections it will be None.

why?

Pyramid ships with support for a single Session, which is bound to request.session. That design is great for many/most web applications, but as your applications scale, your needs may grow:

  • If you have a HTTP site that uses HTTPS for account management, you may need to support separate Sessions for HTTP and HTTPS, otherwise a "man in the middle" or network traffic spy could use HTTP cookie to access the HTTPS endpoints.
  • Client-side Sessions and signed cookies are usually faster, but sometimes you have data that needs to be saved as server-side Sessions because it has security implications (like a third-party oAuth token) or is too big.
  • You may have multiple interconnected apps that each need to save/share isolated bits of Session data.

built-in pyramid_debugtoolbar support!

Just add to your "development.ini" or equivalent configuration method

debugtoolbar.includes = pyramid_session_multi.debugtoolbar

The debugtoolbar will now have a SessionMulti panel which has the following info:

  • configuration data on all Session namespaces
  • ingress Request values of all accessed Sessions
  • egress Response values of all accessed Sessions

The SessionMulti panel can also be enabled to track Sessions on every Request, regardless of the Sessions being accessed or not.

There are two ways to enable the extended Session display used by the :guilabel:SessionMulti panel.

#. Under the :guilabel:Settings tab in the navigation bar, click the red :guilabel:X mark. When there is a green :guilabel:check mark, each request will have the ingress and egress data tracked and displayed on the :guilabel:Settings panel output regardless of the Session being accessed during the request. When there is a red :guilabel:X mark, only requests which accessed the Session will have the ingress and egress data displayed.

#. Send a pdtb_active cookie on a per-request basis. This panel's name for cookie activation is "session_multi".

What does the Panel look like?

Python package

How does this library work?

Instead of registering one Session factory to request.session, this library creates a Request attribute request.session_multi and registers the various session factories to namespaces provided within it.

request.session_multi is a special dict that maps the namespace keys to your ISession compliant Sessions. Sessions are lazily created on-demand, so you won't incur any costs/cookies/backend-data until you use them.

This should work with most Session libraries written for Pyramid. Pyramid's session support mostly just binds a Session factory to the request.session property. Most libraries and implementations of Pyramid's ISession interface act completely independent of the framework and implement of their own logic for detecting changes and deciding what to do when something changes.

This library has been used in production for several years with:

Miscellaneous

There are a few "safety" checks for conflicts.

  1. A pyramid.exceptions.ConfigurationError will be raised if a namespace of Session factory is null
  2. A pyramid.exceptions.ConfigurationError will be raised if a namespace or factory or cookie name is re-used.

A given factory instance can not be re-used, because that can cause conflicts with cookies or backend storage keys.

You can re-use a single cookie library/type multiple times by creating a factory for each setting (see the example above, which re-uses SignedCookieSessionFactory twice).

If you do not register a factory with a cookie_name, this library will try to derive one based on a ._cooke_name attribute. If neither option is available, an Exception will be raised on configuration.

What if Sessions should only run in certain situations?

register_session_factory accepts a kwarg for discriminator, which is a function that expects a single argument of a Request object.

If provided and the discriminator function returns an non-True value, the .session_multi namespace will be set to None, otherwise the namespace will be populated with the result of the factory.

License

MIT

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