Using Docker in Development

Docker support is a new feature in Pegasus as of October 2020. Please report any issues and watch this page for updates.

Pegasus optionally includes support for Docker during development. The Docker development setup can also be used as a foundation for deploying to containerized platforms. See our deployment page for more details.

Prerequisites

You need to install both Docker and Docker Compose prior to setting up your environment.

Windows users may also need to install a 3rd-party package to run make commands. The easiest way to do that is via these instructions.

Getting Started

First set up your Pegasus project with Docker enabled and using Postgres as a database following the getting started guide.

Enter the project directory

cd {{ project_name }}

Run the initialization script

make init

This will spin up a database, web worker, celery worker, and Redis broker and create and run your database migrations.

Note: users of older versions of Windows may need to install “make” separately to use it. Alternatively, you can just inspect the Makefile in the repository and run the commands manually (e.g. docker-compose up -d).

Load server

Visit http://localhost:8000/ in a browser and you should be up and running!

Using the Makefile

Pegasus ships with a self-documenting Makefile that will run common commands for you, including starting your containers, performing database operations, and building your front end.

You can run make to see list helper functions, and you can view the source of the Makefile file in case you need to add to it or run any once-off commands.

For example, you can run management commands in containers using the same method used in the Makefile. E.g.

docker-compose exec web python manage.py createsuperuser

Architecture and how it works

Containers

The Docker configuration is primarily in docker-compose.yml.

There are four containers that start: a Postgres database, a Redis instance (for caching and use as a Celery broker), a web container running your Django process, and a Celery container for background jobs.

Settings

The docker environment sets environment variables using the included .env.dev file. This file also tells your Docker environment to use settings_docker.py (which extends settings.py) as the DJANGO_SETTINGS_MODULE.

The .env.dev file is automatically ignored by git, so you can put any additional secrets there. It generally should not be checked into source control.

Python environments

The Python environment is run in the containers, which means you do not need to have your own local environment if you are always using Docker for development. Python requirements are automatically installed when the container builds.

However, keep in mind that if you go this route, you will need to run all commands inside the containers as per the instructions below.

Running once-off management commands

Running commands on the server can be done using docker-compose, by following the pattern used in the Makefile.

For example, to bootstrap Stripe subscriptions, run:

docker-compose exec web python manage.py bootstrap_subscriptions

Or to promote a user to superuser, run:

docker-compose exec web python manage.py promote_user_to_superuser me@example.com

Commonly used commands can be added to the Makefile for convenience.

Updating Python packages

If you add or modify anything in your requirements.txt files, you will have to rebuild your containers. This can be done by running:

docker-compose build

After than you can run

make start

to run your project with the latest dependencies.

Other Resources