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:

• Create Dockerfile - Define container image

• Build Image - docker build -t myapp .

• 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));

});