Docker Skill

Purpose

Containerization for development and deployment.

When Active

User mentions Docker, container, deployment.

Expertise

Dockerfile Patterns

• •Multi-stage builds
• •Layer optimization
• •Caching strategies
• •Security scanning

Docker Compose

• •Service definition
• •Volume management
• •Network configuration
• •Environment variables

Build Optimization

• •Layer ordering
• •.dockerignore
• •BuildKit features
• •Cache mounts

Production Patterns

• •Minimal base images
• •Non-root user
• •Health checks
• •Signal handling

Volume Management

• •Named volumes
• •Bind mounts
• •Volume drivers
• •Backup strategies

Network Configuration

• •Bridge networks
• •Overlay networks
• •Service discovery
• •Load balancing

Patterns

Multi-stage Node.js Build

FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM node:20-alpine AS runner
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY package*.json ./
RUN npm ci --omit=dev
CMD ["node", "dist/index.js"]

Development Compose

version: '3.8'
services:
  app:
    build: .
    volumes:
      - .:/app
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=development
  db:
    image: postgres:15
    volumes:
      - postgres-data:/var/lib/postgresql/data
    environment:
      - POSTGRES_PASSWORD=secret

volumes:
  postgres-data:

Production Compose

version: '3.8'
services:
  app:
    image: registry.example.com/app:latest
    environment:
      - NODE_ENV=production
      - DATABASE_URL=${DATABASE_URL}
    restart: unless-stopped
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:3000/health"]

.dockerignore

node_modules
npm-debug.log
.git
.env
*.md

Best Practices

• •Use specific version tags
• •Run as non-root user
• •Minimize layers
• •COPY before RUN for cache
• •Use health checks
• •Don't bundle development dependencies

Dependencies

• •Docker Engine 20+
• •Docker Compose v2