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

dockerfile

# 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

yaml

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

dockerfile

# ✅ 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

yaml

# ✅ 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

bash

# 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