Docker Compose for Django development#

I had to get Docker Compose working for a Django project, primarily to make it easier for other developers to get a working development environment.

Some features of this project:

Uses GeoDjango, so needs GDAL etc for the Django app plus a PostgreSQL server running PostGIS
Already has a Dockerfile used for the production deployment, but needed a separate one for the development environment
Makes extensive use of Django migrations (over 100 and counting)

I ended up with this docker-compose.yml file in the root of the project:

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version: "3.1"
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volumes:
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  postgresql-data:
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services:
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  database:
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    image: postgis/postgis:13-3.1
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    restart: always
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    expose:
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      - "5432"
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    ports:
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      - "5432:5432"
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    volumes:
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      - postgresql-data:/var/lib/postgresql/data
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    environment:
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      POSTGRES_USER: postgres
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      POSTGRES_DB: mydb
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      POSTGRES_PASSWORD: postgres
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  web:
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    container_name: myapp
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    platform: linux/amd64
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    build:
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      context: .
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      dockerfile: Dockerfile.dev
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    command: python manage.py runserver 0.0.0.0:3000
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    environment:
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      DATABASE_URL: postgres://postgres:postgres@database:5432/mydb
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      DEBUG: 1
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    volumes:
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      - .:/app
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    ports:
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      - "3000:3000"
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    depends_on:
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      - migrations
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      - database
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  migrations:
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    platform: linux/amd64
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    build:
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      context: .
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      dockerfile: Dockerfile.dev
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    command: python manage.py migrate --noinput
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    environment:
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      DATABASE_URL: postgres://postgres:postgres@database:5432/mydb
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    volumes:
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      - .:/app
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    depends_on:
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      - database

The db container runs PostGIS. It uses a named volume to persist PostgreSQL data in between container restarts.

The web container runs the Django development server, built using the custom Dockerfile.dev Dockerfile.

The migrations container simply runs the apps migrations and then terminates - with depends_on used to ensure that migrations run after the hdatabase server starts and before the web server.

Both web and migrations include a platform: linux/amd64 property - this ensures they will work on M1 Macs even if the Python dependencies are not yet easily compiled for that architecture, see Running Docker on an M1 Mac.

The container_name: myapp field on the web container is a convenience which means you can later run commands like this:

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docker exec -it myapp ./manage.py collectstatic

Here’s Dockerfile.dev:

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FROM python:3.9-slim
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ENV APP_HOME /app
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WORKDIR $APP_HOME
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ENV PYTHONUNBUFFERED 1
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# gdal for GeoDjango
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RUN apt-get update && apt-get install -y \
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    binutils \
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    gdal-bin \
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    libproj-dev \
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    git \
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    && rm -rf /var/lib/apt/lists/*
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COPY requirements.txt .
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RUN pip install --no-cache-dir -r requirements.txt
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WORKDIR $APP_HOME/myapp
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RUN ./manage.py collectstatic --no-input
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CMD python manage.py runserver 0.0.0.0:3000