Dockerizing Express.js (Node.js framework) application

Lets run simple express.js application using docker.

This articles assumes you already have docker desktop installed on your development machine.

We will achieve this by creating a Dockerfile and a docker-compose.yml files at the root of our application source code.

Dockerfile is a text file that contains the commands to create our docker image. And another utility called Compose by making use of docker-compose.yml file will run this container as a service for us.

Step 1: Create express barebone application

git clone [https://github.com/swapnil00patil/micro8](https://github.com/swapnil00patil/micro8) 
cd express
												OR
npx express-generator (https://expressjs.com/en/starter/generator.html)

Step 2: Create a Dockerfile

FROM node:15.12.0

WORKDIR /app

COPY entrypoint.sh /entrypoint.sh
RUN chmod +x /entrypoint.sh

ADD . .

RUN npm install

ENTRYPOINT ["/entrypoint.sh"]

We start by defining the base image to host our application in.

/app is a directory where we host our source code.

ADD . . copies the source code from source code on host machine over to container’s /app directory.

We run npm install inside the image.

And finally we create entrypoint.sh.

Step 3: Create entrypoint.sh

We are not doing much here. But lets keep it separate so we can extend it as required.

#!/bin/sh

DEBUG=express:* npm start

exec "$@"

Step 4 docker-compose.yml

version: '3.8'

services:
  dev:
    build: 
      context: ./
      dockerfile: Dockerfile
    volumes:
      - ./:/app
    ports:
      - '4000:4000'

And finally run docker compose up in the terminal at the root of your application.

Your application will be running at http://localhost:3000.