Seed Data

To be useful, staging environments almost always require seed data to be injected into the staging database. To do this you have the following solutions:

Seeding using a predefined set of objects

If you can test all your features from a limited set of predefined objects, you can take advantage of the seeding capabilities offered by your application framework (e.g. Rails seed data). In that case, you can simply add the seeding process as a one-off service in your Docker Compose configuration.

Example:

# docker-compose.yml
version: '3'
networks:
  - backend
  - frontend
services:
  db:
    image: postgres
    networks:
      - backend
  web:
    build: .
    command: bundle exec rails s
    ...
    networks:
      - backend
      - frontend
    depends_on:
      - db
      - seeder
  seeder:
    command: bundle exec rails db:seed
    restart: on-failure
    networks:
      - backend
    depends_on:
      - db

Notice the restart: on-failure restart policy for the seeder service, ensuring it is only run once.