docker-patterns

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---
name: docker-patterns
description: Docker and Docker Compose patterns for local development, container security, networking, volume strategies, and multi-service orchestration.
origin: ECC
---

# Docker Patterns

Docker and Docker Compose best practices for containerized development.

## When to Activate

- Setting up Docker Compose for local development
- Designing multi-container architectures
- Troubleshooting container networking or volume issues
- Reviewing Dockerfiles for security and size
- Migrating from local dev to containerized workflow

## Docker Compose for Local Development

### Standard Web App Stack

```yaml
# docker-compose.yml
services:
  app:
    build:
      context: .
      target: dev                     # Use dev stage of multi-stage Dockerfile
    ports:
      - "3000:3000"
    volumes:
      - .:/app                        # Bind mount for hot reload
      - /app/node_modules             # Anonymous volume -- preserves container deps
    environment:
      - DATABASE_URL=postgres://postgres:postgres@db:5432/app_dev
      - REDIS_URL=redis://redis:6379/0
      - NODE_ENV=development
    depends_on:
      db:
        condition: service_healthy
      redis:
        condition: service_started
    command: npm run dev

  db:
    image: postgres:16-alpine
    ports:
      - "5432:5432"
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres
      POSTGRES_DB: app_dev
    volumes:
      - pgdata:/var/lib/postgresql/data
      - ./scripts/init-db.sql:/docker-entrypoint-initdb.d/init.sql
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      timeout: 3s
      retries: 5

  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"
    volumes:
      - redisdata:/data

  mailpit:                            # Local email testing
    image: axllent/mailpit
    ports:
      - "8025:8025"                   # Web UI
      - "1025:1025"                   # SMTP

volumes:
  pgdata:
  re

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  "skill": "imp-48514f27-1148-4a1f-8d36-c3fee22038d1",
  "messages": [{ "role": "user", "content": "…" }]
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