Docker Patterns

Docker Patterns Skill

Overview

This skill provides guidelines for building production-ready Docker containers, multi-stage builds, security hardening, Docker Compose orchestration, and deployment best practices.

Quick Reference

Multi-Stage Build Example

# Build stage
FROM node:18-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

# Production stage
FROM node:18-alpine
RUN addgroup -g 1001 -S nodejs && adduser -S nodejs -u 1001
WORKDIR /app
COPY --from=builder --chown=nodejs:nodejs /app/dist ./dist
COPY --from=builder --chown=nodejs:nodejs /app/node_modules ./node_modules
USER nodejs
EXPOSE 3000
HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
  CMD node -e "require('http').get('http://localhost:3000/health', (r) => {process.exit(r.statusCode === 200 ? 0 : 1)})"
CMD ["node", "dist/main.js"]

Docker Compose Development

version: '3.8'
services:
  app:
    build:
      context: .
      dockerfile: Dockerfile.dev
    ports:
      - "3000:3000"
    volumes:
      - .:/app
      - /app/node_modules
    environment:
      - NODE_ENV=development

Core Principles

1. Multi-Stage Builds

• Separate build and runtime environments
• Minimize final image size
• Don't include build tools in production

2. Security Hardening

• Run as non-root user
• Use specific image tags (not latest)
• Scan images for vulnerabilities
• Drop unnecessary capabilities

3. Layer Caching

• Order instructions by change frequency
• Copy package files before source code
• Use .dockerignore to exclude unnecessary files

4. Health Checks

• Implement /health endpoints
• Configure Docker health checks
• Set appropriate intervals and timeouts

Language-Specific Examples

See detailed guides in references/:

• Dockerfile Patterns - Multi-stage builds for Node.js, Python, Go, Rust
• Docker Compose Patterns - Development, production, and multi-environment setups
• Container Security - Security hardening, scanning, and best practices
• Deployment Patterns - Blue-green, rolling updates, Kubernetes

Dockerfile Best Practices

# ✅ DO: Use specific tags
FROM node:18.19.0-alpine3.18

# ✅ DO: Combine RUN commands
RUN apt-get update && \
    apt-get install -y --no-install-recommends curl && \
    rm -rf /var/lib/apt/lists/*

# ✅ DO: Create non-root user
RUN addgroup -g 1001 -S appgroup && \
    adduser -S appuser -u 1001 -G appgroup
USER appuser

# ✅ DO: Copy with ownership
COPY --chown=appuser:appgroup . /app

# ✅ DO: Add health check
HEALTHCHECK --interval=30s --timeout=3s --retries=3 \
  CMD wget --quiet --tries=1 --spider http://localhost:3000/health || exit 1

Docker Compose Best Practices

# ✅ DO: Use environment files
services:
  app:
    env_file:
      - .env.production

# ✅ DO: Set resource limits
deploy:
  resources:
    limits:
      cpus: '0.5'
      memory: 512M

# ✅ DO: Configure health checks
healthcheck:
  test: ["CMD", "wget", "--spider", "http://localhost:3000/health"]
  interval: 30s
  timeout: 10s
  retries: 3

Image Scanning

# Using Trivy
docker run --rm -v /var/run/docker.sock:/var/run/docker.sock \
  aquasec/trivy:latest image myapp:latest

# Using Docker Scout
docker scout cves myapp:latest

# Using Snyk
snyk container test myapp:latest

When to Use This Skill

Use this skill when:

• Creating Dockerfiles for production applications
• Setting up development environments with Docker Compose
• Optimizing image sizes with multi-stage builds
• Hardening containers for security
• Setting up health checks and monitoring
• Managing multiple environments (dev/staging/prod)
• Implementing CI/CD pipelines with Docker
• Troubleshooting container issues

Related Skills

• @ci-cd-pipelines - Continuous integration and deployment with GitHub Actions
• @security-best-practices - Container security and vulnerability scanning
• @feature-development - Development workflow
• @python-patterns - Python-specific patterns
• @go-conventions - Go-specific patterns
• @ts-react-nextjs - Node.js patterns