<p>Docker is an open platform for developing, shipping, and running applications. Docker enables you to separate your applications from your infrastructure so you can deliver software quickly.&nbsp;With Docker, you can manage your infrastructure in the same ways you manage your applications. By taking advantage of Docker’s methodologies for shipping, testing, and deploying code quickly, you can significantly reduce the delay between writing code and running it in production. In this tutorial we will be dockerize a simple node app. Let's get started.</p><p><br></p><h2>Create a Node.js app</h2><p>Initialize your project</p><pre class="ql-syntax" spellcheck="false">npm init -y
</pre><p><br></p><p>A package.json file that describes your app will be generated.Install <a href="https://expressjs.com/" rel="noopener noreferrer" target="_blank">express</a>:</p><pre class="ql-syntax" spellcheck="false">npm i express
</pre><p>Your package.json will look as below:</p><pre class="ql-syntax" spellcheck="false">{
  "name": "nodeapp",
  "version": "1.0.0",
  "description": "",
  "author": "",
  "main": "app.js",
  "scripts": {
    "start": "node app.js"
  },
  "dependencies": {
    "express": "^4.17.1"
  }
}
</pre><p><br></p><p>Then, create a app.js file and create a basic node server with express.</p><pre class="ql-syntax" spellcheck="false">'use strict';

const express = require('express');
const app = express();

app.get('/', (req, res) =&gt; {
  res.send('I am dockerized node app');
});

const PORT = 8000;
const HOST = '0.0.0.0';

app.listen(PORT, HOST);
console.log(`Server is running at http://${HOST}:${PORT}`);
</pre><p><br></p><h2>Creating a Dockerfile</h2><p>We'll look at how you can run this app inside a Docker container using the official Docker image. First, you'll need to build a Docker image of your app.Create an empty file called Dockerfile:</p><pre class="ql-syntax" spellcheck="false">touch Dockerfile
</pre><p>Open the Dockerfile in your favorite text editor</p><p>The first thing we need to do is define from what image we want to build from. Here we will use the latest LTS (long term support) version 14 of node available from the <a href="https://hub.docker.com/_/node" rel="noopener noreferrer" target="_blank">Docker Hub</a>:</p><pre class="ql-syntax" spellcheck="false">FROM node:14
</pre><p>Next we create a directory to hold the application code inside the image, this will be the working directory for your application:</p><pre class="ql-syntax" spellcheck="false"># Create app directory
WORKDIR /usr/src/app
</pre><p>This image comes with Node.js and NPM already installed so the next thing we need to do is to install your app dependencies using the npm binary.</p><p><br></p><blockquote>if you are using npm version 4 or earlier a package-lock.json file will <em>not</em> be generated.</blockquote><h2><br></h2><pre class="ql-syntax" spellcheck="false"># Install app dependencies
# A wildcard is used to ensure both package.json AND package-lock.json are copied
# where available (npm@5+)
COPY package*.json ./

RUN npm install
# If you are building your code for production
# RUN npm ci --only=production
</pre><p><br></p><blockquote>Note that, rather than copying the entire working directory, we are only copying the package.json file. This allows us to take advantage of cached Docker layers. bitJudo has a good explanation of this <a href="http://bitjudo.com/blog/2014/03/13/building-efficient-dockerfiles-node-dot-js/" rel="noopener noreferrer" target="_blank">here</a>. Furthermore, the npm ci command, specified in the comments, helps provide faster, reliable, reproducible builds for production environments. You can read more about this <a href="https://blog.npmjs.org/post/171556855892/introducing-npm-ci-for-faster-more-reliable" rel="noopener noreferrer" target="_blank">here</a>.</blockquote><p><br></p><p>To bundle your app's source code inside the Docker image, use the COPY:</p><pre class="ql-syntax" spellcheck="false"># Bundle app source
COPY . .
</pre><p>Your app binds to port 8000 so you'll use the EXPOSE instruction to have it mapped by the docker daemon:</p><pre class="ql-syntax" spellcheck="false">EXPOSE 8000
</pre><p>Last but not least, define the command to run your app using CMD which defines your runtime. Here we will use node server.js to start your server:</p><pre class="ql-syntax" spellcheck="false">CMD [ "node", "app.js" ]
</pre><p>Your Dockerfile should now look like this:</p><pre class="ql-syntax" spellcheck="false">FROM node:14

WORKDIR /usr/src/app

COPY package*.json ./

RUN npm install

COPY . .

EXPOSE 8000
CMD [ "node", "app.js" ]
</pre><h2><br></h2><h2>.dockerignore file</h2><p>Create a .dockerignore file in the same directory as your Dockerfile with following content:</p><pre class="ql-syntax" spellcheck="false">node_modules
npm-debug.log
</pre><p><br></p><p>This will prevent your local modules and debug logs from being copied onto your Docker image and possibly overwriting modules installed within your image.</p><p><br></p><h2>Building your image</h2><p>Go to the directory that has your Dockerfile and run the following command to build the Docker image. The -t flag lets you tag your image so it's easier to find later using the docker images command:</p><pre class="ql-syntax" spellcheck="false">docker build -t &lt;your username&gt;/nodeapp .
</pre><p>Your image will now be listed by Docker:</p><pre class="ql-syntax" spellcheck="false">docker images
</pre><h2><br></h2><h2>Run the image</h2><p>Running your image with -d runs the container in detached mode, leaving the container running in the background. The -p flag redirects a public port to a private port inside the container. Run the image you previously built:</p><pre class="ql-syntax" spellcheck="false">docker run -p 3000:8000 -d &lt;your username&gt;/nodeapp
</pre><p>If you visit http://localhost:3000 then you'll get an output as "I am dockerized node app"</p><p><br></p><p>Happy Coding ...</p>

Dockerizing a Nodejs web app

Related blogs

About us: