Docker compose extend

duplicating a Redis service in every docker-compose file, today I learned that compose configurations can be shared across file and projects.

// monorepo/docker-compose.yml
version: "3"

services:
  redis:
    image: redis:5.0.6
    ports:
      - 6379:6379

  (...) // other shared dependencies

// monorepo/packages/my-service/docker-compose.yml
version: "3"

services:
  redis:
    extends:
      file: ../../docker-compose.yml
      service: redis

  (...) // other service dependencies

In this setup, Redis is added to the top-level docker-compose file and is extended in the services docker-compose file. If we now up the service with yarn workspace my-service up it will check for Redis in the top-level up it, and continue to add the dependencies as they are defined in the services docker-compose.