Docker Containerization: From Development to Production

Docker has become essential for modern development. This guide covers everything from basics to production deployment.

Why Docker?

Benefits

• Consistency: Same environment everywhere
• Isolation: No dependency conflicts
• Portability: Run anywhere Docker runs
• Efficiency: Lighter than VMs
• Scalability: Easy horizontal scaling

Dockerfile Best Practices

Multi-Stage Builds

Keep images small:

# Build stage
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build
Production stage
FROM node:20-alpine
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
CMD ["node", "dist/index.js"]

Layer Caching

Order commands strategically:

# Dependencies change less often - cache these
COPY package*.json ./
RUN npm ci
Source code changes frequently
COPY . .

Security

Run as non-root:

RUN addgroup -S app && adduser -S app -G app
USER app

Docker Compose

Development Setup

version: '3.8'
services:
  app:
    build: .
    volumes:
      - .:/app
      - /app/node_modules
    ports:
      - "3000:3000"
    environment:
      - DATABASE_URL=postgres://postgres:password@db:5432/app
    depends_on:
      - db
  
  db:
    image: postgres:15-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data
    environment:
      - POSTGRES_PASSWORD=password
volumes:   postgres_data:

Production Considerations

Health Checks

HEALTHCHECK --interval=30s --timeout=3s --retries=3   CMD curl -f http://localhost:3000/health || exit 1

Resource Limits

services:
  app:
    deploy:
      resources:
        limits:
          cpus: '0.5'
          memory: 512M

Logging

Use JSON logging for aggregation:

{"level":"info","message":"Server started","port":3000}

Networking

Bridge Networks

Create isolated networks:

networks:
  backend:
    driver: bridge
  frontend:
    driver: bridge

Conclusion

Docker simplifies development and deployment. Master these patterns to build reliable, scalable containerized applications.