Can push notifications be done with an AngularJS+Flask stack?

Question

I have a Python/Flask backend and an Angular frontend for my website. At the backend there is a process that occasionally checks SQS for messages and I want it to push a notification to the client which can then in turn update an Angular controller. What is the best way to do this my existing technologies?

Answer 1

To be able to push to the client, you'll have to implement web socket support in some fashion. If you want to keep it in python/flask, there is this tutorial on how to do that with gevent:

http://www.socketubs.org/2012/10/28/Websocket_with_flask_and_gevent.html

In that article, Geoffrey also mentions a SocketIO compatible library for python/gevent that may allow you to leverage the SocketIO client-side JS library, called "gevent-socketio".

That may reduce how much work you have to do in terms of cross-browser compatibility since SocketIO has done a lot of that already.

Here is a pretty good tutorial on how to use SocketIO in AngularJS so that you can notify the AngularJS model when an event comes in from SocketIO:

http://www.html5rocks.com/en/tutorials/frameworks/angular-websockets/

If you don't want to host the web socket backend, you could look to a hosted service like PubNub or Pusher and then integrate them into AngularJS as a service. You can communicate with these services through your Python app (when the SQS notification happens) and they'll notify all connected clients for you.

Answer 2

I know this is a bit late, but I have done pretty much exactly what you ask for (though without Angular).

I ended up having a separate process running a websocket server called Autobahn , which listens to a redis pub/sub socket, the code is here on github

This allows you to send push notifications to your clients from pretty much anything that can access redis.

So when I want to publish a message to all my connected clients I just use redis like this:

r = redis.Redis()
r.publish('broadcasts', "SOME MESSAGE")

This has worked fairly good so far. What I can't currently do is send a push notification to a specific client. But if you have a authentication system or something to identify a specific user you could tie that to the open websockets and then be able to send messages directly to a specific client :-)

You could of course use any websocket server or client (like socket.io or sock.js), but this has worked great for me :-)