Dockerize a Node app and deploy to Heroku

Prerequisites

Node
npm
Docker

1. Create a node.js app

First, let’s create a simple node.js(express) application, to get started with express.

Create project by running npm init -y and copy paste the following lines in package.json file.

{
  “name”: “heroku_docker”,
  “version”: “1.0.0”,
  “description”: “Deploy Dockerized NodeJS Image app on Heroku”,
  “main”: “index.js”,
  “scripts”: {
     “start”: “node index.js”,
     “dev”: “nodemon index.js”
  },
  “author”: “”,
  “license”: “ISC”,
  “dependencies”: {
    "dotenv": "^16.0.0",
    "express": "^4.18.1",
    "nodemon": "^2.0.16"
  }
}

Create a file named index.js which is our express app, and add the following.

const express = require("express");
require("dotenv").config();
const PORT = process.env.PORT || 3000;
const app = express();
app.use("/", (req, res, next) => {
  res.send("Node JS backend is running");
});
app.listen(PORT, () => {
  console.log(`Server is listing on PORT : ${PORT}`);
});

Create .env file and add PORT

PORT=3000

Now, let’s try to run our app in the terminal,

$ npm install
$ npm start

Open Browser and type localhost:3000

2. Set up the Dockerfile

The next step is to create a Dockerfile.

If you haven’t installed docker in your system, visit here to download it.

Dockerfile: you can think of the Dockerfile as a receipt — it includes instructions on how to create a Docker image
Docker image: the output of the Dockerfile run — this is the runnable unit
Add the following in Dockerfile

FROM node:alpine
# CREATE APP DIRECTORY
RUN mkdir -p /app
WORKDIR /app
# INSTALL DEPENDENCIES
COPY package*.json ./
RUN npm install
COPY . .
# Exports
EXPOSE 3000
CMD ["npm","start"]

FROM node:alpine — From the base image node, with alpine variant.

WORKDIR — We are mentioning that the directory called app is going to hold our project. If the directory specified doesn’t exist in the image, it is newly created.

COPY package*.json ./— We are copy our package.json and package-lock.json to our workdir.

RUN npm install — This command installs the dependencies mentioned in our package.json.

CMD [ "npm", "start"] — Executes npm start , which is the command to run our app.

3. Login to Heroku and create app

Run the following commands to login in heroku and create app on heroku. Copy the name of Heroku App.

$ heroku login
$ heroku container:login
$ heroku create

4. Build the image using Dockerfile

Being in your project directory, run the following command.

$ docker build -t registry.heroku.com/<HEROKU_APP_NAME>/web .
e.g docker build -t registry.heroku.com/heroku-docker01/web .

$ docker push registry.heroku.com/<HEROKU_APP_NAME>/web
e.g docker push registry.heroku.com/heroku-docker01/web

$ heroku container:release web -a <HEROKU_APP_NAME>
e.g heroku container:release web -a heroku-docker01

After Image release on heroku app click on open app in heroku.

Github repo — https://github.com/Abdullah0332/heroku-docker

Happy Learning!!

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Dockerize a Node app and deploy to Heroku

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