How to Write Docker Compose Files

1. platform

as not everyone is using the same environment (some are using MacOS for example which is targeting arm64 instead of amd64), it is advised to add this option to target the right architecture

docker-compose platform:

services:
  serviceName:
    platform: linux/x86_64
  # ...

2. Wait for a service to be healthy before starting another one

If you have a service that depends on another one, it is important to wait for the dependent service to be healthy before starting the dependent one. This can be achieved using the depends_on option with the condition: service_healthy condition.

Here is an example where serviceB depends on serviceA being healthy before it starts:

services:
  serviceA:
    # ...
    healthcheck:
      test: [CMD, curl, -f, http://localhost:8080/health]
      interval: 30s
      timeout: 10s
      retries: 3
  serviceB:
    # ...
    depends_on:
      serviceA:
        condition: service_healthy

In this example, api service will wait for the db service to be healthy before it starts. The health check for the db service is defined to check if the MySQL server is responding to ping requests.

version: '2.1'
services:
  api:
    build: .
    container_name: api
    ports:
      - 8080:8080
    depends_on:
      db:
        condition: service_healthy
  db:
    container_name: db
    image: mysql
    ports:
      - '3306'
    environment:
      MYSQL_ALLOW_EMPTY_PASSWORD: yes
      MYSQL_USER: user
      MYSQL_PASSWORD: password
      MYSQL_DATABASE: database
    healthcheck:
      test: [CMD, mysqladmin, ping, -h, localhost]
      timeout: 20s
      retries: 10