Quart Session [2021-09-05]

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 while Quart-Session uses a JSON serializer capable of 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

Back-end usage

At any point you may interface with the session back-end directly:

@app.route("/")
async def hello():
    cache = app.session_interface
    await cache.set("random_key", "val", expiry=3600)
    data = await cache.get("random_key")

The interface will have the get, set, and delete methods available (regardless of back-end - similar to how aiocache works).

Performance

flask-session sets a session for each incoming request, including static files. From experience, this often puts unneeded load on underlying session infrastructure, especially in high-traffic environments.

Quart-Session only contacts the back-end when a session changed (or created). In addition, static file serves never emit a Set-Cookie header. If you'd like to enable this though, 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 web applications that require extra security.

app = Quart(__name__)
app.config['SESSION_TYPE'] = 'redis'
app.config['SESSION_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_REVERSE_PROXY to True.

Future development

  • MongoDBSessionInterface
  • FileSystemSessionInterface
  • GoogleCloudDatastoreSessionInterface
  • Pytest

Flask-Session

This library works very similarly to flask-session. The changes are specified below:

  • Quart-Session does not emit a Set-Cookie on every request.
  • Quart-Session does not emit a Set-Cookie on static file serves.
  • 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.
  • Quart-Session can do session protection.
  • Quart-Session might not have all the back-end interfaces implemented (yet), such as "filesystem".

Help

Find the Quart folk on gitter or open an issue.

License

BSD

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