Flask-uWSGI-WebSocket

High-performance WebSockets for your Flask apps powered by uWSGI. Inspired by Flask-Sockets.

from flask import Flask
from flask.ext.uwsgi_websocket import WebSocket

app = Flask(__name__)
ws = WebSocket(app)

@ws.route('/echo')
def echo(ws):
    while True:
        msg = ws.receive()
        ws.send(message)

if __name__ == '__main__':
    app.run(debug=True, threads=16)

Installation

To install Flask-uWSGI-WebSocket, simply:

$ pip install Flask-uWSGI-WebSocket

Deployment

You can use uWSGI's built-in HTTP router to get up and running quickly:

$ uwsgi --master --http :8080 --http-websockets --wsgi-file app.py

...or call app.run, passing uwsgi any arguments you like:

app.run(debug=True, host='localhost', port=8080, master=true, processes=8)

uWSGI supports several concurrency models, in particular it has nice support for Gevent. If you want to use Gevent, import flask.ext.uwsgi_websocket.GeventWebSocket and configure uWSGI to use the gevent loop engine:

$ uwsgi --master --http :8080 --http-websockets --gevent 100 --wsgi-file app.py

...or:

app.run(debug=True, gevent=100)

For production you'll probably want to run uWSGI behind Haproxy or nginx of course, instead of using the built-int HTTP router. Explore the uWSGI documentation for more detail.

Development

It's possible to take advantage of Flask's interactive debugger by installing werkzeug's DebuggedApplication middleware:

from werkzeug.debug import DebuggedApplication
app.wsgi_app = DebuggedApplication(app.wsgi_app, True)

...and running uWSGI with only a single worker:

$ uwsgi --master --http :8080 --http-websockets --wsgi-file --workers 1 --threads 8 app.py

If you use app.run(debug=True), Flask-uWSGI-Websocket will do this automatically for you.

API

Flask-uWSGI-Websocket automatically performs the WebSocket handshake for you and passes your route handler a websocket client exposing uWSGI's WebSocket API.

websocket.recv()

websocket.send(msg)

websocket.send_binary(msg)

websocket.recv_nb()

websocket.send_from_sharedarea(id, pos)

websocket.send_binary_from_sharedarea(id, pos)

In addition there is a special websocket.receive() method which tries to make non-blocking calls simpler. When using the WebSocket plugin, it blocks making it appropriate for threaded or multiprocess concurrency models. When using GeventWebSocket it'll take advantage of gevent and make a non-blocking recv call. AsyncWebsocket should do roughly the same thing, but currently plain --async concurrency model is a bit buggy in uWSGI 2.0.