Docker Deployment Skill

Master containerizing and deploying Node.js applications with Docker for consistent, portable deployments.

Quick Start

Dockerize Node.js app in 3 steps:

1. Create Dockerfile - Define container image
2. Build Image - docker build -t myapp .
3. Run Container - docker run -p 3000:3000 myapp

Core Concepts

Basic Dockerfile

FROM node:18-alpine

WORKDIR /app

COPY package*.json ./
RUN npm ci --only=production

COPY . .

EXPOSE 3000

CMD ["node", "src/index.js"]

Multi-Stage Build (Optimized)

# Build stage
FROM node:18-alpine AS builder

WORKDIR /app

COPY package*.json ./
RUN npm ci --only=production

COPY . .

# Production stage
FROM node:18-alpine

WORKDIR /app

# Copy from builder
COPY --from=builder /app/node_modules ./node_modules
COPY --from=builder /app .

# Create non-root user
RUN addgroup -g 1001 -S nodejs && \
    adduser -S nodejs -u 1001

USER nodejs

EXPOSE 3000

HEALTHCHECK --interval=30s --timeout=3s \
  CMD node healthcheck.js || exit 1

CMD ["node", "src/index.js"]

Learning Path

Beginner (1-2 weeks)

• ✅ Understand Docker basics
• ✅ Create simple Dockerfile
• ✅ Build and run containers
• ✅ Manage volumes and networks

Intermediate (3-4 weeks)

• ✅ Multi-stage builds
• ✅ Docker Compose
• ✅ Environment variables
• ✅ Health checks

Advanced (5-6 weeks)

• ✅ Image optimization
• ✅ Production best practices
• ✅ Container orchestration
• ✅ CI/CD integration

Docker Compose

# docker-compose.yml
version: '3.8'

services:
  app:
    build: .
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=production
      - DATABASE_URL=postgresql://db:5432/myapp
      - REDIS_URL=redis://redis:6379
    depends_on:
      - db
      - redis
    restart: unless-stopped

  db:
    image: postgres:15-alpine
    environment:
      - POSTGRES_USER=myapp
      - POSTGRES_PASSWORD=secret
      - POSTGRES_DB=myapp
    volumes:
      - postgres-data:/var/lib/postgresql/data

  redis:
    image: redis:7-alpine
    volumes:
      - redis-data:/data

  nginx:
    image: nginx:alpine
    ports:
      - "80:80"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf:ro
    depends_on:
      - app

volumes:
  postgres-data:
  redis-data:

Docker Compose Commands

# Start services
docker-compose up -d

# View logs
docker-compose logs -f app

# Stop services
docker-compose down

# Rebuild images
docker-compose up -d --build

# Scale services
docker-compose up -d --scale app=3

.dockerignore

node_modules
npm-debug.log
.git
.gitignore
.env
.env.local
.vscode
*.md
tests
coverage
.github
Dockerfile
docker-compose.yml

Docker Commands

# Build image
docker build -t myapp:latest .

# Run container
docker run -d -p 3000:3000 --name myapp myapp:latest

# View logs
docker logs -f myapp

# Enter container
docker exec -it myapp sh

# Stop container
docker stop myapp

# Remove container
docker rm myapp

# List images
docker images

# Remove image
docker rmi myapp:latest

# Prune unused resources
docker system prune -a

Environment Variables

# In Dockerfile
ENV NODE_ENV=production
ENV PORT=3000

# Or in docker-compose.yml
environment:
  - NODE_ENV=production
  - PORT=3000

# Or from .env file
env_file:
  - .env.production

Volumes for Persistence

services:
  app:
    volumes:
      - ./logs:/app/logs              # Bind mount
      - node_modules:/app/node_modules # Named volume

volumes:
  node_modules:

Health Checks

# In Dockerfile
HEALTHCHECK --interval=30s --timeout=3s --start-period=5s \
  CMD node healthcheck.js || exit 1

// healthcheck.js
const http = require('http');

const options = {
  host: 'localhost',
  port: 3000,
  path: '/health',
  timeout: 2000
};

const request = http.request(options, (res) => {
  console.log(`STATUS: ${res.statusCode}`);
  process.exit(res.statusCode === 200 ? 0 : 1);
});

request.on('error', (err) => {
  console.log('ERROR:', err);
  process.exit(1);
});

request.end();

Image Optimization

# Use Alpine (smaller base image)
FROM node:18-alpine  # 180MB vs node:18 (1GB)

# Multi-stage build (remove build dependencies)
# Use .dockerignore (exclude unnecessary files)
# npm ci instead of npm install (faster, deterministic)
# Only production dependencies
RUN npm ci --only=production

# Combine RUN commands (fewer layers)
RUN apk add --no-cache git && \
    npm ci && \
    apk del git

Production Best Practices

FROM node:18-alpine

# Don't run as root
RUN addgroup -g 1001 -S nodejs && \
    adduser -S nodejs -u 1001

WORKDIR /app

COPY --chown=nodejs:nodejs package*.json ./
RUN npm ci --only=production

COPY --chown=nodejs:nodejs . .

USER nodejs

# Health check
HEALTHCHECK CMD node healthcheck.js || exit 1

# Use node instead of npm start (better signal handling)
CMD ["node", "src/index.js"]

Docker Hub Deployment

# Login
docker login

# Tag image
docker tag myapp:latest username/myapp:1.0.0
docker tag myapp:latest username/myapp:latest

# Push to Docker Hub
docker push username/myapp:1.0.0
docker push username/myapp:latest

# Pull from Docker Hub
docker pull username/myapp:latest

CI/CD with GitHub Actions

name: Docker Build & Deploy

on:
  push:
    branches: [main]

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v3

      - uses: docker/setup-buildx-action@v2

      - uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKER_USERNAME }}
          password: ${{ secrets.DOCKER_PASSWORD }}

      - uses: docker/build-push-action@v4
        with:
          push: true
          tags: username/myapp:latest
          cache-from: type=gha
          cache-to: type=gha,mode=max

Common Issues & Solutions

Node modules caching

# Cache node_modules layer
COPY package*.json ./
RUN npm ci
COPY . .  # This doesn't rebuild node_modules

Signal handling

# Use node directly (not npm)
CMD ["node", "src/index.js"]

# In app: Handle SIGTERM
process.on('SIGTERM', () => {
  server.close(() => process.exit(0));
});

When to Use

Use Docker deployment when:

• Need consistent environments (dev, staging, prod)
• Deploying microservices
• Want easy scaling and orchestration
• Using cloud platforms (AWS, GCP, Azure)
• Implementing CI/CD pipelines

Related Skills

• Express REST API (containerize APIs)
• Database Integration (multi-container setup)
• Testing & Debugging (test in containers)
• Performance Optimization (optimize images)

Resources

• Docker Documentation
• Docker Compose
• Node.js Docker Best Practices