Sunday, December 19, 2010

How To Influence Twisted With Django

This is probably taken as the concept for a horror novel by many, but bare with me as I am going somewhere productive with this line of thought. There are a number of valuable ideas in Django, even if they aren’t original. I think some of the concepts could be interesting if applied to Twisted. We can’t start over, but maybe we could bridge the gap.

The Project

A “Project” is a very vague concept that we all start when we’re doing something new, but in a system like Django it is a codified piece of the framework. What a project is, how it is structured, and where its boundaries lie are all documented carefully. This provides an obvious starting point and creates a wonderful sense of consistency from one project to the next.

The Application

Within a Django project one or more Django applications are combined, and each application provides a unit of reusable functionality. This might consist of DB models and views to aid in tagging objects, providing search indexes, or generating thumbnails from uploaded photos. Like the Project itself, the application is documented by Django in terms of its boundaries and structure.

If Twisted Took A Page From the Django Book?

I think we can make a case for borrowing these concepts and patterns. The running theme is breaking large things up into reusable chunks and defining the boundaries and interactions in ways that we can connect them largely via configuration. Can this work with Twisted? I think it can, in specific areas.

We can probably borrow the Project unit directly, add a script to every project that runs twistd and loads commands, like the manage.py in Django. A standard settings module to configure a project is an obvious choice.

At the next level we would configure smaller, reusable parts the project would bring together. Instead of a urls.py, we might define a ports.py, which we use to map the interfaces we listen on and the services that handle them.

I think we can’t map “Application” to any one concept, but need a variety of types of reusable things. That is fine and Django does the same. We talk about apps all the time, but we also have Request Middleware, Context Middleware, etc. Twisted has a lot of room for configurable middleware.

This is certainly something that deserves more thought.

2 comments:

Jean-Paul Calderone said...

Hey Calvin,

I can't help but love the idea of learning from other projects. Please keep thinking and writing about this topic! :)

About the specific idea of having something like `settings.py`, I have to disagree though. `settings.py` is one of my least favorite things about django projects. I don't want a pile of Python code defining a heap of global state for my project. Global state sucks! The problem settings.py is tackling is the same as the problem .tac files are tackling, I think. I think that neither one solves the problem _particularly_ well. Moving to a settings.py-like thing would just be lateral movement at best.

As far as manage.py goes, maybe you can talk about how having a copy of manage.py in every project is better than having one copy of twistd. What does manage.py get me that twistd doesn't?

Marius Gedminas said...

I think the phrase is 'bear with me', unless you're in a naturalist beach. ;-)

I write here about programming, how to program better, things I think are neat and are related to programming. I might write other things at my personal website.

I am happily employed by the excellent Caktus Group, located in beautiful and friendly Carrboro, NC, where I work with Python, Django, and Javascript.

Blog Archive