Docker Compose

One file for the whole local stack

Docker Compose starts several containers together, with networking between them by service name:

services:
  api:
    build: .
    ports: ["8080:8080"]
    environment:
      DATABASE_URL: postgresql://app:app@db:5432/app    # "db" is the service name
      REDIS_URL: redis://cache:6379
    depends_on:
      db:
        condition: service_healthy
  db:
    image: postgres:17
    environment:
      POSTGRES_USER: app
      POSTGRES_PASSWORD: app
    volumes: ["pgdata:/var/lib/postgresql/data"]
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U app"]
      interval: 5s
  cache:
    image: redis:7
volumes:
  pgdata:

docker compose up -d --build     # build and start everything
docker compose logs -f api
docker compose exec db psql -U app
docker compose down              # stop (add -v to delete volumes too)

Where Compose fits

Compose is ideal for local development and CI integration tests: everyone gets the same stack with one command. In production you'd use Kubernetes, ECS, Cloud Run, Azure Container Apps or similar, which add scheduling across machines, self-healing and rolling deployments.

from graphlib import TopologicalSorter

depends_on = {"api": {"db", "cache"}, "worker": {"db", "cache"}, "db": set(), "cache": set()}
order = list(TopologicalSorter(depends_on).static_order())
print("start order:", order)

start order: ['cache', 'db', 'api', 'worker']