docker-compose.yml

# version: "3.9"

services:
  app: #name of service. each docker compose 'service' represents a container
    #my understanding is each service/container can be built from a dockerfile (like what we have specified immediately below for this 'app' service using the 'build' instruction, or can be based off a pre-existing image like we have done in the 'db' service below using the 'image' instruction
    build:
      context: .
      args:
        - DEV=true
    ports:
      - "8000:8000"
    volumes:
      - ./app:/app

    # this over-rides any default command specified in a 'CMD' instruction in the image Dockerfile
    command: > 
      sh -c "python manage.py runserver 0.0.0.0:8000"
    environment:
      - DB_HOST=db #the variable name is set to 'db' which is the name of the database service below
      # The values for database name, user and password below match what we have defined under the database service below:
      - DB_NAME=devdb
      - DB_USER=devuser
      - DB_PASS=changeme
    depends_on:
      - db #this instructs docker to start the 'db' service before starting this 'app' service

  db:
    #image:postgres:13-alpine
    image: postgres
    volumes:
      - dev-db-data:/var/lib/postgresql/
    environment: #below variables are used to configure database for running locally NOT IN PRODUCTION, hence the loose way for creating and storing the username/password
      - POSTGRES_DB=devdb
      - POSTGRES_USER=devuser
      - POSTGRES_PASSWORD=changeme

volumes:
  dev-db-data:

# "docker-compose" is replaced by "docker compose" which is made available via "docker-compose-plugin" package that gets bundled with Docker Desktop.


# build image using this command (after cd'ing into the project's root dir):
#   docker compose build
# helpful options
#  --no-cache:        force Docker to pull fresh dependencies
#  --progress=plain   verbose mode for troubleshooting


#run the server using:
#  docker compose up