How to Package an Express.JS application as a multi-container application with Docker compose

This tutorial is designed to show how you can package an ExpressJS application as a multi-container application with Docker compose.

You will learn to:

Prerequisites

Node.js. If Node.js is not installed on your system, you can download the installer from the Downloads page.
Docker. For details on installing Docker, see the Install Docker page.

Initialize a new project and install the dependenices

Install the Ghost command-line tool globally by entering the following command:

 npm init -y

 Wrote to /Users/andrei/Documents/test/docker-compose-tutorial/package.json:

 {
   "name": "docker-compose-tutorial",
   "version": "1.0.0",
   "description": "",
   "main": "index.js",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1"
   },
   "keywords": [],
   "author": "",
   "license": "ISC"
 }

Install dependencies:

 npm install express mysql --save

 npm notice created a lockfile as package-lock.json. You should commit this file.
 npm WARN docker-compose-tutorial@1.0.0 No description
 npm WARN docker-compose-tutorial@1.0.0 No repository field.

 + express@4.17.1
 + mysql@2.18.1
 added 59 packages from 48 contributors and audited 139 packages in 4.187s
 found 0 vulnerabilities

Create a a file called app.js with the following content:

 const express = require('express')
 const app = express()
 const port = 3000
 var mysql = require('mysql')

 const con = mysql.createConnection({
   host: "localhost",
   user: "yourusername",
   password: "yourpassword",
   database: "yourdatabase"
 })

 con.connect(function(err) {
   if (err) throw err;
   console.log("Connected!");
 })

 const sql1 = 'CREATE TABLE IF NOT EXISTS `visitors` (`count` int)'
 con.query(sql1, function (err, result) {
   if (err) throw err;
 })

 const sql2 = "INSERT INTO visitors (count) VALUES ('0')";
   con.query(sql2, function (err, result) {
     if (err) throw err;
     console.log("1 record inserted");
   })


 app.get('/', (req, res) => {
   con.query("SELECT count FROM visitors", function (err, result, fields) {
     if (err) throw err;
     let count = result[0].count
     if (count === undefined) {
       count = 0
     } else {
       count ++
       let sql = `UPDATE visitors SET count = ${count}`
       con.query(sql, function (err, result) {
         if (err) throw err;
           console.log("1 record inserted");
       })
     }
     res.send(`You are visitor number ${count}`)
   });
 })

 app.listen(port, () => console.log(`Example app listening at http://localhost:${port}`))

Create a file called Dockerfile and paste in the following content:

 FROM node:10
 WORKDIR /usr/src/app
 COPY . /usr/src/app/
 RUN npm install
 EXPOSE 3000
 CMD [ "node", "app.js" ]

To specify the list of files the Docker engine should ignore when generating the build context, create a file called .dockerignore with the following content:
```
 node_modules
 npm-debug*
```

Build an image for your ExpressJS application. Enter the docker build command, and use the -t flag to specify the name of the image.

Note that the name of the image is in the following format <YOUR-DOCKER-HUB-USERNAME>/<IMAGE_NAME>.

The following example command builds an image named andreipopescu12/docker-compose-expressjs, and sets the path to the context to the current directory:

 docker build -t andreipopescu12/docker-compose-expressjs .

 Sending build context to Docker daemon  23.55kB
 Step 1/6 : FROM node:10
 10: Pulling from library/node
 7568c21980bd: Pull complete
 4a9f2207c812: Pull complete
 6fe350d2b140: Pull complete
 d95a2fdc8b3d: Pull complete
 6e9eb1fbe207: Pull complete
 d56555bcbc0a: Pull complete
 8ca024298cd0: Pull complete
 871d3382b483: Pull complete
 1102201760ac: Pull complete
 Digest: sha256:a5dbd2049787dd255be075ca081f3d0cf4dc0039bef76125aefa43eec25933d4
 Status: Downloaded newer image for node:10
 ---> bd837ed69497
 Step 2/6 : WORKDIR /usr/src/app
 ---> Running in b5f21f51505e
 Removing intermediate container b5f21f51505e
 ---> cd48cfc5a044
 Step 3/6 : COPY . /usr/src/app/
 ---> 58f2d49bc5c1
 Step 4/6 : RUN npm install
 ---> Running in 28b54252e691
 npm WARN docker-compose-tutorial@1.0.0 No description
 npm WARN docker-compose-tutorial@1.0.0 No repository field.

 added 59 packages from 48 contributors and audited 139 packages in 3.1s
 found 0 vulnerabilities

 Removing intermediate container 28b54252e691
 ---> a1225c2f71db
 Step 5/6 : EXPOSE 3000
 ---> Running in b21de6284b90
 Removing intermediate container b21de6284b90
 ---> 8499f6399322
 Step 6/6 : CMD [ "node", "app.js" ]
 ---> Running in e980cdba3c2f
 Removing intermediate container e980cdba3c2f
 ---> bfd59424cbdb
 Successfully built bfd59424cbdb
 Successfully tagged andreipopescu12/docker-compose-expressjs:latest

You can push the docker-compose-expressjs image to Docker Hub by running the following command:

 docker push andreipopescu12/docker-compose-expressjs

 The push refers to repository [docker.io/andreipopescu12/docker-compose-expressjs]
 ee7764a6d718: Pushed
 a3c14e55c76b: Pushed
 2236e41f6d5d: Pushed
 5cc1b11e8894: Mounted from library/node
 4379817b82b1: Mounted from library/node
 c7b80f4f0500: Mounted from library/node
 d7369641c400: Mounted from library/node
 b829f6ba4e1d: Mounted from library/node
 a9286fedbd63: Mounted from library/node
 d50e7be1e737: Mounted from library/node
 6b114a2dd6de: Mounted from library/node
 bb9315db9240: Mounted from library/node
 latest: digest: sha256:cd5ab6b56e384a40ff58705a183f33e86e1dfc4c6e52c10d7868bdc2f5603c82 size: 2841

Docker compose

Create a file named docker-compose.yaml and copy in the following spec:

```YAML
1. Create a file named docker-compose.yml, and copy in the following spec:

  version: "3.7"
  services:
    app:
      container_name: docker-compose-expressjs
      image: andreipopescu12/docker-compose-expressjs
      restart: always
      ports:
        - "3000:3000"
      expose:
        - "3000"
      links:
        - mysql
      depends_on:
        - mysql
    mysql:
      container_name: docker-compose-mysql
      image: mysql/mysql-server:5.7
      ports:
        - "3306:3306"
      expose:
        - "3306"
      environment:
        MYSQL_USER: "yourusername"
        MYSQL_PASSWORD: "yourpassword"
    ```
---
1. Run MySQL

docker run –name=mysql-demo -p 3306:3306
-e MYSQL_USER=yourusername
-e MYSQL_PASSWORD=yourpassword
-e MYSQL_DATABASE=yourdatabase
–mount type=bind,src=$(PWD)/mysql/my.cnf,dst=/etc/my.cnf
–mount type=bind,src=$(PWD)/mysql/datadir,dst=/var/lib/mysql
-d mysql/mysql-server:5.7 ```