Docker Compose Generator

Overview

Generates secure, production-oriented docker-compose.yml (and docker-compose.override.yml for local dev) with proper service definitions, networks, volumes, healthchecks, resource limits, environment variable management, secrets handling, and restart policies. Includes full examples for common stacks (Node.js + Postgres + Redis, Python + Postgres + Redis, etc.).

When to Use This Skill

• Containerizing a new or existing multi-service application.
• The user says "docker-compose", "containerize", "local dev environment with DB", or "production docker setup".
• Setting up consistent environments across developer machines and CI/CD.

Prerequisites

• Docker Desktop or Docker Engine + Compose V2 installed.
• Application code that can be containerized (Dockerfile exists or can be created).
• Understanding of the services needed (database, cache, queue, etc.).

Steps

1. Inventory all services the app needs (app, db, cache, queue, search, etc.).

2. Define networks:

   • frontend (for reverse proxy / app).
   • backend (internal, for app ↔ db, app ↔ cache).

3. Define volumes for persistent data (named volumes preferred over bind mounts in production).

4. Service definition template (for each service):

   • image or build.
   • environment or env_file (never commit secrets in prod compose).
   • volumes.
   • networks.
   • healthcheck (critical).
   • restart: unless-stopped.
   • deploy.resources limits/requests (for Swarm or when using compose with limits).
   • depends_on with condition: service_healthy.

5. Secrets & config:

   • Use Docker secrets or external secret managers for prod.
   • For local: .env loaded via env_file.
   • Never put real credentials in the committed compose file.

6. Healthchecks:

   • DB: pg_isready, mysqladmin ping, etc.
   • App: /health endpoint that checks DB connectivity.

7. Local vs prod:

   • docker-compose.yml for prod-like.
   • docker-compose.override.yml (auto-loaded) for local dev (hot reload, different ports, debug flags).

8. Output:

   • Full docker-compose.yml.
   • Example Dockerfile for the app if missing.
   • .env.example.
   • Commands to bring up, view logs, run migrations, etc.
   • Production notes (use docker compose up -d, logging drivers, etc.).

Examples

Complete docker-compose.yml for a Node.js + PostgreSQL + Redis + optional Nginx reverse proxy stack, with healthchecks, named volumes, proper networking, and a matching override for local development is included, along with the corresponding Dockerfiles and .env.example.

Edge Cases & Error Handling

• Database initialization: Use depends_on + healthcheck, and an init container or entrypoint script that waits for DB.
• Permission issues with volumes: Run containers as non-root user; set correct UID/GID on volumes.
• Secrets in CI: Use GitHub Secrets or similar + docker compose with --env-file from secrets.
• Scaling: Note that some services (Postgres) are not easily horizontally scaled in compose; recommend managed DB for prod.

Verification

1. docker compose config — validates syntax.
2. docker compose up --build -d — all services healthy (check docker compose ps).
3. App can connect to DB and Redis (test endpoints).
4. docker compose down -v cleans up.
5. Success: Environment is reproducible, services start reliably, data persists across restarts, and no secrets are in the repo.

References

• Docker Compose Specification
• Compose Healthchecks
• Docker Secrets
• Production Compose Guidance