Django in Docker on ECS

Environment

I like to use direnv and pyenv to control my environment.

$ touch .env.local
$ touch .envrc
$ touch .gitignore

Add the following to .envrc.

use pyenv 3.9.1
dotenv ".env.local"

Then allow direnv to set up the environment.

direnv allow

Add the following to .gitignore

.direnv
.env.local

Create a src directory where your application source code will live.

mkdir src

Now, you should have a local virtual enviornment set up.

pip install django

Start a requirements file for your application.

pip freeze > src/requirements.txt

Django

Use pip to install a dependency to use dot-files.

pip install python-dotenv
pip freeze > src/requirements.txt

Navigate to the src directory, and start building a Django application.

cd src
django-admin startproject config .

Add the following to .env.local.

ENVIRONMENT=LOCAL

DJANGO_ALLOWED_HOSTS=localhost
DJANGO_SECRET_KEY='<replace-this-with-SECRET-KEY>'
DJANGO_DB_ENGINE=django.db.backends.postgresql

POSTGRES_PASSWORD='<replace-with-some-password>'
POSTGRES_USER=postgres
POSTGRES_HOSTNAME=db
POSTGRES_PORT=5432
POSTGRES_DB=db
POSTGRES_HOST_AUTH_METHOD=trust

Next, configure config/settings.py. We'll tackle the following,

1. Imports, importing os and dotenv
2. Security Key, copy the original to .env.local
3. Debug, set True locally, but False elswhere
4. Allowed Hosts, set to localhost locally
5. Edit the database settings

First, we import os and dotenv and then configure dotenv.

import os
from pathlib import Path

from dotenv import load_dotenv
load_dotenv()

Then copy the existing SECRET_KEY to the .env.local, and refrence it using os.getenv. Add an if-else structure around DEBUG. Reference the ALLOWED_HOSTS variable.

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = os.getenv('DJANGO_SECRET_KEY')

# SECURITY WARNING: don't run with debug turned on in production!
if os.getenv('ENVIRONMENT') == 'LOCAL':
    DEBUG = True
else:
    DEBUG = False

ALLOWED_HOSTS = [
    os.getenv('DJANGO_ALLOWED_HOSTS')
]

Finally, replace the DATABASE variable in config/settings.py with,

DATABASES = {
    'default': {
        'ENGINE':   os.getenv('DJANGO_DB_ENGINE'),
        'NAME':     os.getenv('POSTGRES_DB'),
        'USER':     os.getenv('POSTGRES_USER'),
        'PASSWORD': os.getenv('POSTGRES_PASSWORD'),
        'HOST':     os.getenv('POSTGRES_HOSTNAME'),
        'PORT':     os.getenv('POSTGRES_PORT'),
    }
}

At this point, you might create an app using django-admin startapp <app>. If you do that, then you can follow any number of Django guides on the internet. This is guide provides a bare-minimum and won't (yet) gett into building apps.

Docker

From the command line, outside of the src/ directory,

touch Dockerfile
touch docker-compose.yml

Open Dockerfile and add the following,

# Pull base image
FROM python:3.9.1

# Set environment variables
ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1

# Set working directory
WORKDIR /usr/src/app

# Copy project
COPY src /usr/src/app

# Install dependencies
RUN pip install -r /usr/src/app/requirements.txt

# Expose port 8000
EXPOSE 8000

# Start the web server
CMD python manage.py runserver 0.0.0.0:8000

Open docker-compose.yml and add the following,

version: '3.8'
services:
  app:
    build:
      context: ./
      dockerfile: Dockerfile
    depends_on:
      - db
    env_file:
      - .env.local
    ports:
      - 8000:8000
    volumes:
      - ./src:/usr/src/app
  db:
    image: postgres:11
    ports:
      - 5432:5432
    volumes:
      - postgres_data:/var/lib/postgresql/data/
    env_file:
      - .env.local

volumes:
  postgres_data:

You should now be able to build an image by running,

docker-compose build

And then you should be able to bring the server up by running,

docker-compose up

If you go to localhost:8000 in a browser, you should see a landiing page with a rocket.