Web Application Development

Code layout

The development of a Twisted Web application should be orthogonal to its deployment. This means is that if you are developing a web application, it should be a resource with children, and internal links. Some of the children might use Nevow, some might be resources manually using .write, and so on. Regardless, the code should be in a Python module, or package, outside the web tree.

You will probably want to test your application as you develop it. There are many ways to test, including dropping an .rpy which looks like:

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from mypackage import toplevel
resource = toplevel.Resource(file="foo/bar", color="blue")

into a directory, and then running:

% twistd web --path=/directory

You can also write a Python script like:

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#!/usr/bin/env python

from twisted.web import server
from twisted.internet import reactor
from mypackage import toplevel

reactor.listenTCP(8080,
    server.Site(toplevel.Resource(file="foo/bar", color="blue")))
reactor.run()

Web application deployment

Which one of these development strategies you use is not terribly important, since (and this is the important part) deployment is orthogonal. Later, when you want users to actually use your code, you should worry about what to do -- or rather, don't. Users may have widely different needs. Some may want to run your code in a different process, so they'll use distributed web (twisted.web.distrib). Some may be using the twisted-web Debian package, and will drop in:

% cat > /etc/local.d/99addmypackage.py
from mypackage import toplevel
default.putChild("mypackage", toplevel.Resource(file="foo/bar", color="blue"))
^D

If you want to be friendly to your users, you can supply many examples in your package, like the above .rpy and the Debian-package drop-in. But the ultimate friendliness is to write a useful resource which does not have deployment assumptions built in.

Understanding resource scripts (.rpy files)