How to Dockerize Node.js Applications A Step-by-Step Guide

Docker containerization has transformed application development, offering consistency, scalability, and simplified dependency management. This guide provides a step-by-step approach to Dockerizing Node.js applications using npm.

What is Docker?

Docker is a platform that uses containers to run applications in isolated environments. Key components include Docker images, containers, and Dockerfiles. Containers are lightweight and share the host OS, making them more efficient than virtual machines.

Why Use Docker?

• Consistency: Ensure the same environment across development, testing, and production.

• Isolation: Secure and separate applications.

• Scalability: Easily scale applications and manage dependencies.

Getting Started with Docker

1. Install Docker on your system from the official Docker website.

2. Basic Docker Commands:

   • docker run: Run a container.

   • docker ps: List running containers.

   • docker stop: Stop a container.

   • docker rm: Remove a container.

   • docker build: Build an image from a Dockerfile.

3. Basic Docker Compose Commands:

   • docker-compose up: Build, (re)create, start, and attach to containers.

   • docker-compose down: Stop and remove containers, networks, images, and volumes.

   • docker-compose ps: List containers.

   • docker-compose stop: Stop running containers.

   • docker-compose rm: Remove stopped service containers.

   • docker-compose build: Build or rebuild services.

   • docker-compose logs: View output from containers.

Dockerizing your Node.js Application

Step 1: Create .dockerignore

# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.

# dependencies
/node_modules
/.pnp
.pnp.js

# testing
/coverage

# production
/build

# misc
.DS_Store
.env
.env.local
.env.development.local
.env.test.local
.env.production.local

npm-debug.log*
yarn-debug.log*
yarn-error.log*

Step 2: Create a Dockerfile : (if using yarn)

FROM node:20-alpine AS builder

WORKDIR /app

COPY package.json yarn.lock ./

RUN yarn install

COPY . .

FROM node:20-alpine

WORKDIR /app

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

EXPOSE 8000

CMD ["yarn", "start"]

If using npm :

# Stage 1: Build the application
FROM node:20-alpine AS builder

WORKDIR /app

COPY package.json package-lock.json ./

RUN npm install

COPY . .

# Stage 2: Run the application
FROM node:20-alpine

WORKDIR /app

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

EXPOSE 3000

CMD ["npm", "start"]

Step 3: Create a docker-compose.yml file:

version: "3"
services:
  easy-express: #keep the name accordingly your application
    build:
      dockerfile: Dockerfile
      context: ./
    container_name: easy-express #keep the name accordingly your application
    ports:
      - "8000:8000"
    restart: always
    volumes:
      - .:/app
      - /app/node_modules
    env_file:
      - .env
    dns:
      - 8.8.8.8
      - 8.8.4.4
    networks:
      - app-network

networks:
  app-network:

Step 4: Build and Run the Docker Container

docker-compose up --build

Step 5: List containers.

docker ps

Step 6: Stop and remove containers, networks, images, and volumes.

docker-compose down

Output :