Linking Containers across Multiple Docker Compose Projects

docker-compose.1.yml

version: '3.2'

networks:
  default:
    external:
      name: my_net # Needs to be manually created using docker network create

services:
  nginx:
    image: jwilder/nginx-proxy
    ports:
      - '80:80'
    volumes:
      - /var/run/docker.sock:/tmp/docker.sock:ro

  db:
    image: postgres

  web_one:
    build: .
    depends_on:
      - db
      - nginx
    volumes:
      - .:/app
    environment:
      - RAILS_ENV=development
      - VIRTUAL_HOST=app_one.local

docker-compose.2.yml

version: '3.2'

networks:
  default:
    external:
      name: my_net # Needs to be manually created using docker network create

services:
  web_two:
    build: .
    volumes:
      - .:/app
    depends_on:
      - db
      - nginx
    environment:
      - RAILS_ENV=development
      - VIRTUAL_HOST=app_two.local
      # Optionally use a different database on the same postgres container.
      # - POSTGRES_DB=app_two_development

shell.sh

$ docker network create my_net
$ docker-compose -f docker-compose.1.yml run --rm web_one bin/rails db:setup
$ docker-compose -f docker-compose.1.yml -f docker-compose.2.yml up -d
$ open http://app_one.local http://app_two.local