I am creating a web app which needs to continuously poll my django web server to get an update. Is there a way avoid this polling? Like server can send push messages on update or the client registers a callback for an event and server triggers the callback whenever something changes.
I know there are signaling frameworks in ASP.net etc. but I want something which can work with Django.
Thanks
Fundamentally web sockets, part of HTML5, were design for this purpose, ie bi-directional communication between clients and servers through the http protocol, while its being highly talked about few application servers have implemented and even fewer http servers have actually even began supporting it.
While there are some packages:
django-websocket
django-socketio
that have enabled it in django, they don't do anything about your http server, very rarely if ever do you use django standalone, this is because django isn't very efficient for distributing static content such as images or any other static files, as well as distribute work load, we rely on things like nginx, apache and such things for this. unfortunately they don't support web sockets, yet, as such they tend to break the communication between the client and the application server even if its initiated in the first place, depending on implementation.
From my own personal experience nginx would break the communication after 60 seconds since this was the default allotted time for anything open.
As far as I know node.js maybe the best server, currently, for working with web sockets.
Depending on what you are tying to achieve and If regular polling seems in efficient you can try long-polling, basically the connection is held open, until theres new data to be pushed back unto the client vs regular polling, which is done at some interval, note that you may have to configure your http server not to terminate pro-long open connections and run django multithreaded, since each connection will use an instance.
Related
I got a existing software project, that has a relatively primitive plugin system and wanted to expand it by providing a web interface.
Since my application processes realtime data, websockets are the only option besides web rtc.
My previous attempt used zeromq domain sockets on the python side and a server in Node js that connected to the domain socket.
This solution works great and has some benefits over the plugin server, but I want to offer a simpler option for folks that don't need the benefits and don't want the extra complexity.
How would you go about implementing this and is it even possible to do so?
Otherwise, I'll still do a separate process, but use fastapi to build the stuff around the socket endpoint and start it up using subprocess to spawn a second process that also connects to the domain socket.
Hope my question is not stupid, or a rtfm case.
I am facing a situation where I have an Express server and a Flask server, each responsible for various tasks. We are piping a request from Express through to the Flask server, and would like to use sockets to provide heartbeat style updates from the Flask server to the Express server.
Is it possible to use sockets like this? I admit to having never really used sockets for backend stuff before. I've used Socket.io to connect React-based sites with an Express backend, but I'm not sure how to connect two servers like this.
Any help would be greatly appreciated.
There is a Flask extension for Socket.io.
Even though the blurb text says "Flask-SocketIO gives Flask applications access to low latency bi-directional communications between the clients and the server", "clients" doesn't have to mean "frontend".
Since you've already used Socket.io and websockets, you might see if that package meets your need. Certainly easier than reaching immediately for Unix sockets if it turns out you don't have to. :)
NOTE: Flask is not concurrent. It can't handle more than one request at a time by default, because it runs on a single thread and doesn't do async/await stuff. This is more broadly a Python/WSGI problem than specifically a Flask problem. Depending on what you do, this may become a bottleneck in your app.
Automatic threading with Flask
WSGI is synchronous
I'm building a turn-based game and I'm hoping to implement client-server style networking. I really just need to send the position of a couple of objects and some other easily encodable data. I'm pretty new to networking, although I've coded some basic stuff in socket and twisted. Now, though, I need to be able to send the data to a computer that isn't on my local network, and I can't do port forwarding since I don't have admin access to the router and I'm also not totally sure that would do the trick anyways since I've never done it. So, I was thinking of running some Flask or Bottle or Django, etc. code off PythonAnywhere. The clients would then send data to the server code on PythonAnywhere, and when the turn passed, the other client would just go look up the information it needed on the server. I guess then the server would act as just a data bank with some simple getter and setter methods. My question is how can this be implemented? Can my Socket code on my client program talk to my Flask code on PythonAnywhere?
Yes, client code can talk to your project at PythonAnywhere, as you will be given a unique project url like http://yourblogname.pythonanywhere.com/. Your server will listen the 80 port at that url.
It depends what sort of connection your clients need to make to the server. PythonAnywhere supports WSGI, which means "normal" HTTP request/response interactions -- GET, POST, etc. That works well for "traditional" web pages or web apps.
If your client side needs dynamic, two-way connections using non-HTTP protocols, using raw sockets, or even websockets, PythonAnyhwere doesn't support that at present.
The scenario is
I have multiple local computers running a python application. These are on separate networks waiting for data to be sent to them from a web server. These computers are on networks without a static IP and generally behind firewall and proxy.
On the other hand I have web server which gets updates from the user through a form and send the update to the correct local computer.
Question
What options do I have to enable this. Currently I am sending csv files over ftp to achieve this but this is not real time.
The application is built on python and using django for the web part.
Appreciate your help
Use a REST API. Then you can post information to your Django app over HTTP, using an authentication key if necessary.
http://www.django-rest-framework.org/ should help you get started quickly
Sounds like you need a message queue.
You would run a separate broker server which is sent tasks by your web app. This could be on the same machine. On your two local machines you would run queue workers which connect to the broker to receive tasks (so no inbound connection required), then notify the broker in real time when they are complete.
Examples are RabbitMQ and Oracle Tuxedo. What you choose will depend on your platform & software.
Recently I've been doing a lot of testing around different ways of serving our Django application. I've settled on uwsgi as it seems to fit our needs pretty well.
I've recently discovered that uwsgi also supports WebSockets and started looking into it and found some examples: https://github.com/unbit/uwsgi/blob/master/tests/
After running the example (websockets_chat.py) and taking a look through uwsgi's documention for their websockets implementation it appears as though you can only send broadcast, or global messages.
Has anyone managed to find a way to transmit a message to a particular user or does uwsgi not support that level of communication yet?
Cheers
There is nothing like broadcast or global messages in websockets specs. They only "upgrades" an http connection to a lower-level one. What you do with that connection is up to you. The examples show integration with redis as message exchanger but you are free to make other uses.
For your specific case you will need to build a shared list of connected users and implements routing. Remember, you cannot rely on node.js way as it is based on a single threaded setup so everything is way simpler. In uWSGI a websocket connection can happens on a thread, a process or a coroutine, so exchanging data between them is the key.