Dockerizing a Node.js application [2024 revised]

#docker #node

For this tutorial, I will assume you are starting a brand new Node.js application. If you already have a Node.js application you want to Dockerize, head over to Step 3.

*Before starting this tutorial, please make sure you have Docker downloaded.

Step 1

Initialize a new node.js app with

npm init

This will give you a package.json file that looks something like this

// package-lock.json
{
  "name": "sample_app",
  "version": "1.0.0",
  "description": "My First Dockerized Codebase",
  "author": "Your Name",
  "main": "app.js",
  "scripts": {
    "start": "node app.js"
  },
  "dependencies": {
    "express": "^4.17.1"
  }
}

then run npm i (previously npm install) which will generate a package-lock.json.

Step 2

Next, we will create an app.js file

// app.js
const express = require('express');
const app = express();

const PORT = [Your-port-here];

app.get('/', (req, res) => {
  res.send('Hello World');
});

app.listen(PORT, '0.0.0.0' () => {
  console.log('Server listening on Port ${PORT}');
});

Step 3

Here comes the fun part...
First, create a Dockerfile

touch Dockerfile

Inside the Dockerfile, you will need to define the following:

# you can find your node version with: node --version
FROM node:15

# Create app directory
WORKDIR /app

# Install app dependencies
COPY package*.json ./

# Install dependecies
RUN npm install

# Bundle app
COPY . .

# Define your port
EXPOSE 3000

# Tell Docker how to run your app
CMD [ "node", "app.js" ]

Step 4

Additional files are needed for Docker to successfully build your app.

.dockerignore

node_modules/
# anything else you want for Docker to ignore

docker-compose.yml

version: '3.7'   # you can find yours with python --version
services:    
    web:
        image: [your-image-name]
        build: .
        command: node app.js
        ports: 
            - "4040:4040"
        volumes: 
            - ./[your-image-name]/app
            - /app/node_modules
        depends_on:
            - mongodb
    mongodb:
        image: "mongo"
        ports:
            - "27017:27017"