Docker Compose Generator

The modern Compose spec

Compose V2 (the plugin shipped with Docker Desktop and modern Docker Engine) follows the Compose Specification. The version: key is deprecated; the generator omits it. Top-level keys are services, networks, volumes, configs and secrets.

Service anatomy

A production-leaning service looks like this:

services:
  web:
    image: nginx:1.27-alpine
    restart: unless-stopped
    ports:
      - "80:80"
    volumes:
      - ./public:/usr/share/nginx/html:ro
    depends_on:
      app:
        condition: service_healthy
    networks:
      - frontend
      - backend
    healthcheck:
      test: ["CMD", "wget", "--spider", "-q", "http://localhost/health"]
      interval: 30s
      timeout: 5s
      retries: 3

Volumes: bind mount vs named

• Bind mount (./app:/var/www) ties the container to a path on the host; great for local development because changes reflect immediately.
• Named volume (pgdata:/var/lib/postgresql/data) is managed by Docker and persists independent of any host path; the right choice for databases and anything you do not want to delete accidentally with rm -rf.
• Anonymous volume - avoid. It survives restarts but disappears on docker compose down -v without warning.

Networks

By default Compose creates a network named after the project and connects every service to it. Declaring explicit networks is useful when:

• You want to isolate a database from a public-facing service.
• You need a bridge with a custom subnet to align with existing infrastructure.
• You want to attach containers to a pre-existing external network (external: true).

Common mistakes to avoid

• Version key conflicts. version: "3.8" at the top prevents newer features like healthcheck start_interval from working in old Compose; the generator omits the version key.
• Port quoting. 8080:80 parses as YAML base-60 in some edge cases; the generator always quotes port mappings.
• Hard-coded secrets. Secrets written directly into compose.yml end up committed to git. Keep them in an env_file or in the platform’s secret store instead.
• depends_on without condition. Plain depends_on: [db] waits for the container to start, not the service to be ready. Use condition: service_healthy and add a healthcheck to the dependency.