How to use Gevents with Falcon?

Question

I am trying to use Falcon web framework with async workers like gevents and asyncio. I have been looking around for tutorials, but I haven't been able to find any which combine implementation of gevent with falcon. Since I have never used gevents before, I am not sure how to go around testing this combination. Can someone guide me to an example or a tutorial?

Thank you! :)

Discoloration

Answer 1

I was just looking to build a new website with Falcon and gevent, something I had done in the past. I knew that there was something odd about it, so I searched online and found your question. I'm somewhat surprised no one has responded yet. So, I went back to have a look at my earlier code and the following is the basic skeleton to get up and running with Falcon and gevent (which makes for a very fast framework):

from gevent import monkey, pywsgi  # import the monkey for some patching as well as the WSGI server
monkey.patch_all()  # make sure to do the monkey-patching before loading the falcon package!
import falcon  # once the patching is done, we can load the Falcon package


class Handler:  # create a basic handler class with methods to deal with HTTP GET, PUT, and DELETE methods
    def on_get(self, request, response):
        response.status = falcon.HTTP_200
        response.content_type = "application/json"
        response.body = '{"message": "HTTP GET method used"}'

    def on_post(self, request, response):
        response.status = falcon.HTTP_404
        response.content_type = "application/json"
        response.body = '{"message": "POST method is not supported"}'

    def on_put(self, request, response):
        response.status = falcon.HTTP_200
        response.content_type = "application/json"
        response.body = '{"message": "HTTP PUT method used"}'

    def on_delete(self, request, response):
        response.status = falcon.HTTP_200
        response.content_type = "application/json"
        response.body = '{"message": "HTTP DELETE method used"}'

api = falcon.API()
api.add_route("/", Handler())  # set the handler for dealing with HTTP methods; you may want add_sink for a catch-all
port = 8080
server = pywsgi.WSGIServer(("localhost", port), api)  # address and port to bind, and the Falcon handler API
server.serve_forever()  # once the server is created, let it serve forever

As you can see, the big trick is in the monkey-patching. Other than that, it really is quite straightforward. Hope this helps someone!

Hendel

This setup worked great for me. It's worth noting that not only can Falcon itself work with gevents, but you can also take advantage of gevents constructs like spawn, sleep and Semaphore within your app. I used them to create background workers that ran independently from request-driven code. – Federalist

I also tried running Falcon using the Bjoern server as opposed to gevent-enabled pywsgi. The former is faster and can support higher sustained requests/sec based on some of my hello-world testing, but the event loop is opaque and you can't use gevent in your app code. @kvaruni's setup lets you tap into the gevent event loop. That's certainly something to consider when selecting a WSGI server to host Falcon. – Federalist

you should not pass the Handler() class to the add_route, but rather an instance of the class (ref). Other than that I upvoted since it was useful, thanks! – Sigmon