Sane Django Development with Docker

09 Oct 2015 code

Recently I started a new Django project, and this time I decided to go all in on Docker. No virtualenvs, no local databases - containers all the way.

There are about a million and ten articles about how to dockerize webapps by now. However, none of them seem to address one simple fact: we don't simply want to dockerize our applications, we want to develop them too!

sane-django-docker contains a sample django project webapp as well as the necessary config files to run both a development and production server.

Checkout and Go®

One of my goals was to make the codebase development first. One should be able to checkout the codebase and run at most two or three commands to have a real development environment set up. This means we should have a live-reloading Django development server, debug mode on, and a postgresql database. I also can't stand logic in my settings.py files, so it is left as vanilla as possible. It will import a local_settings.py file at the end, but besides that it is 100% constants. No os.getenv() to be found.

To start the development server simply run:

docker-compose up

Django will complain about the postgres database not existing so we'll create one:

docker exec sanedjangodocker_db_1 createdb -Upostgres webapp

Sweet Jane! We now have a Django development server running at http://localhost:8000 along with a postgresql database! Make a code change and watch it reload. This is how code was meant to be written.

So what's the secret sauce? A super simple Dockerfile and an equally simple docker-compose.yml file.

Deployment ain't that much harder

So getitng a dev environment up and running is all well and good, but we are going to have to deploy our code at some point. Deployment takes a few additional steps, but then again deployment probably should.

Let's take a look at what we have:

.
├── deploy
│   ├── docker-compose.yml
│   ├── local_settings.py
│   ├── nginx-app.conf
│   ├── supervisor-app.conf
│   ├── uwsgi.ini
│   └── uwsgi_params
├── docker-compose.yml
├── Dockerfile
├── Dockerfile.prod
├── manage.py
├── README.md
├── requirements.txt
└── webapp
    ├── __init__.py
    ├── settings.py
    ├── urls.py
    └── wsgi.py

The deploy/ directory contains all our server configuration files. The directory also includes our local_settings.py which contains our production config. It is included in .gitignore and should not be included in source control!

Dockerfile.prod is our production dockerfile. It is based on Python:3.5, installs nginx, uwsgi and supervisord, copies our config files and finally runs manage.py collectstatic.

Let's build an image from it:

docker build -f Dockerfile.prod -t webapp:latest .

That's it! our production image is ready to go. To test it out locally first, we can run it:

cd deploy/ && docker-compose up

This should start our project in production mode, using the image we just built. Again, we need to initially create the database, and we should probably run migrations too:

docker exec sanedjangodocker_db_1 createdb -Upostgres webapp
docker exec sanedjangodocker_web_1 python3 manage.py migrate

Navigate to localhost:8700 and see your production-ready application being served!

Where to go from here

There are probably a few things you want to tweak for a real project such as the postgresql data volume in deploy/docker-compose.yml, and your ALLOWED_HOSTS setting in local_settings.py.

Of course, the nginx, uwsgi and supervisord config files are pretty basic, and probably should be scrutinized before a real life deploy.

Conclusions

All in all, I've found this to be a pretty frictionless workflow. The one annoyance I have is that both dockerfiles have to be in the top level directory, due to how Docker sends the build context to the server. Besides that there isn't much to complain about - I'll probably use this as a base for my future projects.

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