Quart-Session

Quart-Session is an extension for Quart that adds support for server-side sessions to your application.

Based on flask-session.

Quick start

Quart-Session can be installed via pipenv or pip,

$ pipenv install quart-session
$ pip install quart-session

and requires Python 3.7.0 or higher. A fairly minimal Quart-Session example is,

from quart import Quart, session
from quart_session import Session

app = Quart(__name__)
app.config['SESSION_TYPE'] = 'redis'
Session(app)

@app.route('/')
async def hello():
    session["foo"] = "bar"
    return 'hello'

app.run()

Features

Redis support

via aioredis.

app = Quart(__name__)
app.config['SESSION_TYPE'] = 'redis'
Session(app)

If you already have a aioredis.Client instance and you'd like to share it with the session interface,

app = Quart(__name__)
app.config['SESSION_TYPE'] = 'redis'

@app.before_serving
async def setup():
    cache = await aioredis.create_redis_pool(...)
    app.config['SESSION_REDIS'] = cache
    Session(app)

By default, Quart-session creates a single connection to Redis, while the example above sets up a connection pool.

Trio support

Quart-Session comes with an (experimental) Redis client for use with the Trio eventloop.

from quart_trio import QuartTrio
from quart_session.redis_trio.client import RedisTrio

app = QuartTrio(__name__)
app.config['SESSION_TYPE'] = 'redis'
Session(app)

Memcached support

via aiomcache.

app = Quart(__name__)
app.config['SESSION_TYPE'] = 'memcached'
Session(app)

JSON serializer

flask-session uses pickle for session data, Quart-Session opts for a JSON serializer capable of (de)serializing the usual JSON types, as well as: Tuple, Bytes, Markup, UUID, and DateTime.

JSON as session data allows for greater interoperability with other programs/languages that might want to read session data straight from a back-end.

If for some unholy reason you prefer pickle or your own serializer,

app = Quart(__name__)
app.config['SESSION_TYPE'] = 'redis'
Session(app)

try:
    import cPickle as pickle
except ImportError:
    import pickle

app.session_interface.serialize = pickle

Session control

By default, flask-session sets a session for each incoming request, including static files. From experience, this approach can put unneeded load on underlying session infrastructure, especially in high-traffic environments.

Quart-Session offers control over the session creation. For example, often you'll only need to create a session when a user successfully logs in.

To enable this behaviour, set SESSION_EXPLICIT to True.

app = Quart(__name__)
app.config['SESSION_TYPE'] = 'redis'
app.config['SESSION_EXPLICIT'] = True
Session(app)

@app.route('/')
async def root():
    if session.get('authenticated'):
        return "Welcome back!"
    return "Welcome anonymous!"

@app.route('/login')
async def login():
    session["authenticated"] = True
    session.dirty()  # mark session for saving
    return 'Logged in!'

app.run()

To re-gain the old behaviour of always emitting a Set-Cookie header on static file serves, set SESSION_STATIC_FILE to True.

Session pinning

Associates an user's session to his/her IP address. This mitigates cookie stealing via XSS etc, and is handy for paranoid web applications.

app = Quart(__name__)
app.config['SESSION_TYPE'] = 'redis'
app.config['SESSION_HIJACK_PROTECTION'] = True
Session(app)

Session reuse from a different IP will now result in the creation of a new session, and the deletion of the old.

Important: If your application is behind a reverse proxy, it most likely provides the X-Forwarded-For header which you must make use of by explicitly setting SESSION_HIJACK_REVERSE_PROXY to True.

Future development

The following session interfaces would be nice to have:

• MongoDBSessionInterface
• FileSystemSessionInterface
• GoogleCloudDatastoreSessionInterface

Other to-do's:

• Unit testing
• Documentation (Sphinx)

Migrating from Flask

This library works very similarly to flask-session. The quart_session.sessions APIs are not 100% the same, but unless you are embedded in Flask-Session's internals, a migration should be fairly straightforward. The distinct changes are specified below:

• Quart-Session does not Set-Cookie on (static) files by default.
• Quart-Session might not have all the back-end interfaces implemented (yet), such as "filesystem".
• Quart-Session uses a different serializer: quart.json.tag.TaggedJSONSerializer instead of pickle.
• Quart-Session disallows the client to supply their own made up sid cookie value.

Help

Find the Quart folk on gitter or open an issue.

License

BSD