web.py and gunicorn

Question

My question is basically what's in the title: how can I setup gunicorn to run a web.py app? (Also, if there are any differences, how would I do it on heroku?)

I already have my app running on heroku using the built in cherrypy, but I have not been able to get gunicorn to work with web.py (I just have no idea where to start - I couldn't find any tutorials).

Answer 1

I'm afraid I'm not familar with Heroku, but I can answer your basic question.

gunicorn is a HTTP server for running Python web apps via WSGI. web.py is a framework for creating Python web apps using WSGI.

So you don't really need a tutorial for using both together, as all you need to do is figure out how to pass the WSGI entry point of your web.py application to gunicorn. A WSGI application is just a Python callable with the right interface i.e. it takes certain parameters and returns a certain response. See this WSGI tutorial for more.

The "hello world" application from the web.py tutorial looks like this test.py:

import web

urls = (
    '/', 'index'
)

class index:
    def GET(self):
        return "Hello, world!"

if __name__ == "__main__":
    app = web.application(urls, globals())
    app.run()

But that does not expose the WSGI application which gunicorn needs.

web.py provides a WSGI application via the wsgifunc method of web.application. We can add this to test.py by adding the following after the index class:

# For serving using any wsgi server
wsgi_app = web.application(urls, globals()).wsgifunc()

This is basically what the web.py documentation tells you to do in the deployment section, when using Apache + mod_wsgi - the fact that the Python code is the same for us with gunicorn is not a coincidence because this is exactly what WSGI gives you - a standard way to write the Python so that it can be deployed using any WSGI capable server.

As explained in the gunicorn docs, we can then point gunicorn at the wsgi_app member of the test module as follows:

(tmp)day@office:~/tmp$ gunicorn test:wsgi_app
2012-12-03 23:31:11 [19265] [INFO] Starting gunicorn 0.16.1
2012-12-03 23:31:11 [19265] [INFO] Listening at: http://127.0.0.1:8000 (19265)
2012-12-03 23:31:11 [19265] [INFO] Using worker: sync
2012-12-03 23:31:11 [19268] [INFO] Booting worker with pid: 19268