compose-setup

# Docker Compose Setup Generate `docker-compose.yml` when the application needs multiple services (app + database, app + cache, monorepo services). ## When to use docker-compose - App requires a database (PostgreSQL, MySQL, MongoDB, Redis) - App has multiple independently deployable services - App needs a message broker (RabbitMQ, Kafka) - Monorepo with multiple `Dockerfile` entries Single-service apps with no external dependencies should use a standalone Dockerfile. ## Detection from source code Look for these signals to determine required services: | Pattern in code or config | Service needed | |--------------------------|----------------| | `DATABASE_URL=postgres://` or `pg` dependency | PostgreSQL | | `DATABASE_URL=mysql://` or `mysql2` dependency | MySQL | | `MONGODB_URI` or `mongoose` dependency | MongoDB | | `REDIS_URL` or `ioredis`/`redis` dependency | Redis | | `RABBITMQ_URL` or `amqplib` dependency | RabbitMQ | | `KAFKA_BROKERS` | Kafka | | `.env.example` listing service URLs | Parse each URL for service type | ## Compose template structure ```yaml services: app: build: context: . dockerfile: Dockerfile ports: - "${PORT:-3000}:3000" environment: - NODE_ENV=production - DATABASE_URL=postgresql://postgres:postgres@db:5432/app depends_on: db: condition: service_healthy restart: unless-stopped db: image: postgres:16-alpine environment: POSTGRES_USER: postgres POSTGRES_PASSWORD: postgres POSTGRES_DB: app volumes: - pgdata:/var/lib/postgresql/data healthcheck: test: ["CMD-SHELL", "pg_isready -U postgres"] interval: 5s timeout: 3s retries: 5 restart: unless-stopped volumes: pgdata: ``` ## Common service blocks ### PostgreSQL ```yaml db: image: postgres:16-alpine environment: POSTGRES_USER: postgres POSTGRES_PASSWORD: postgres POSTGRES_DB: app volumes: - pgdata:/var/lib/postgresql/data healthcheck: test: ["CMD-SHELL", "pg_isready -U postgres"] interval: 5s timeout: 3s retries: 5 ``` ### MySQL ```yaml db: image: mysql:8.0 environment: MYSQL_ROOT_PASSWORD: root MYSQL_DATABASE: app MYSQL_USER: app MYSQL_PASSWORD: app volumes: - mysqldata:/var/lib/mysql healthcheck: test: ["CMD", "mysqladmin", "ping", "-h", "localhost"] interval: 5s timeout: 3s retries: 5 ``` ### MongoDB ```yaml mongo: image: mongo:7 environment: MONGO_INITDB_ROOT_USERNAME: root MONGO_INITDB_ROOT_PASSWORD: root volumes: - mongodata:/data/db healthcheck: test: ["CMD", "mongosh", "--eval", "db.adminCommand('ping')"] interval: 5s timeout: 3s retries: 5 ``` ### Redis ```yaml redis: image: redis:7-alpine command: redis-server --appendonly yes volumes: - redisdata:/data healthcheck: test: ["CMD", "redis-cli", "ping"] interval: 5s timeout: 3s retries: 5 ``` ## Monorepo services For monorepos with multiple services under `apps/` or `services/`: ```yaml services: api: build: context: . dockerfile: apps/api/Dockerfile ports: - "3001:3001" depends_on: db: condition: service_healthy web: build: context: . dockerfile: apps/web/Dockerfile ports: - "3000:3000" depends_on: - api ``` Set build context to the repo root so shared packages are accessible. Each Dockerfile handles its own `COPY` paths. ## Rules - Always use named volumes for persistent data - Always add healthchecks for databases and caches - Use `depends_on` with `condition: service_healthy` so the app waits for healthy dependencies - Use `restart: unless-stopped` for all services - Reference env vars from `.env.example` when available - Default to Alpine/slim images for smaller footprint - Pin image versions (e.g. `postgres:16-alpine`, not `postgres:latest`) ## Related Skills - **`env-detection`** — Detect required service connection URLs (DATABASE_URL, REDIS_URL, etc.) to determine which services to include - **`dockerfile-generation`** — Generate the Dockerfile for each service in the compose file