Create simple web app Nodejs with Docker

Published: 2020-12-22

1556 words - 6 min read

How to get a Node.js application into a Docker container?

Steps to create a web application Nodejs with Docker#

Create NodeJS web app
Create a Dockerfile
Build image from Dockerfile
Run image as container
Connect to web app from a browser

Getting started#

Create root folder of project#

$ mkdir simple-nodejs
$ cd simple-nodejs

Init `package.json`#

$ yarn init -y

Add dependencies and scripts in this package.json file

{
  "name": "simple-nodejs",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "scripts": {
    "start": "node index.js",
    "dev": "nodemon index.js"
  },
  "dependencies": {
    "express": "*",
    "nodemon": "*",
    "dotenv": "*",
    "mongoose": "*",
    "axios": "*"
  }
}

Create `index.js` file (in root project)#

Add the following code to run server nodejs with express framework.

const express = require('express');

const app = express();

app.get('/', (req, res) => {
  res.send('Hi there!');
});

const port = process.env.PORT || 3000;

app.listen(port, () => {
  console.log(`Server is running on port ${port}`);
});

Create `Dockerfile`#

$ touch Dockerfile

The first thing we need to do is define from what image we want to build from. Here is the version 12.18.1 of Nodejs from DockerHub
```
FROM node:12.18.1
```
Next we create a directory to hold the application code inside the image. This will be the working directory for your application.
```
# Create app directory
WORKDIR /app
```

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. Please note that if you are using npm version 4 or earlier a package-lock.json file will not be generated.

# 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

To bundle your app's source code inside the Docker image, use the COPY instruction:
```
# Bundle app source
COPY . .
```
Your app binds to port 8080 so you'll use the EXPOSE instruction to have it mapped by the docker daemon:
```
EXPOSE 8080
```
Last but not least, define the command to run your app using CMD which defines your runtime. Here we will use node index.js to start your server as write in scripts of package.json file.
```
CMD ["yarn", "dev"]
```

Your Dockerfile should now look like this:

  # Specify a base image
  FROM node:12.18.1

  # Create app directory
  WORKDIR /app

  # 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 ./

  # Install dependencies
  RUN yarn install
  # If you are building your code for production
  # RUN npm ci --only=production

  # Bundle app source
  COPY . .

  EXPOSE 8080

  # Default command
  CMD [ "yarn", "dev" ]

Create `.dockerignore` file with the following content:#

node_modules
npm-debug.log

Build your image#

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:

$ docker build -t <your username>/node-docker .

Your image will now be listed by Docker:

$ docker images

# Example
REPOSITORY                      TAG        ID              CREATED
node                            12         1934b0b038d1    5 days ago
<your username>/node-web-app    latest     d64d3505b0d2    1 minute ago

Run the image#

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:

$ docker run -p 49160:8080 -d <your username>/node-docker

Print the output of your app:

# Get container ID
$ docker ps

# Print app output
$ docker logs <container id>

# Example
Running on http://localhost:8080

If you need to go inside the container you can use the exec command:

# Enter the container
$ docker exec -it <container id> /bin/bash

Test your Docker container#

To test your app, get the port of your app that Docker mapped:

$ docker ps

# Example
ID            IMAGE                                COMMAND    ...   PORTS
ecce33b30ebf  <your username>/node-docker:latest  npm start  ...   49160->8080

In the example above, Docker mapped the 8080 port inside of the container to the port 49160 on your machine.

Now you can call your app using curl (install if needed via: sudo apt-get install curl):

$ curl -i localhost:49160

HTTP/1.1 200 OK
X-Powered-By: Express
Content-Type: text/html; charset=utf-8
Content-Length: 9
ETag: W/"9-leKwfhJ1TlLDfP1IVUTU9ERZe/8"
Date: Mon, 23 Nov 2020 14:41:00 GMT
Connection: keep-alive

Hi there!

Some useful other commands#

$ docker images #show all images installed
$ docker rmi -f <image id> #remove image by id
$ docker ps #list all containers running
$ docker ps -aq #list all containers (only ids)
$ docker stop <container id> #stop a container
$ docker stop $(docker ps -aq) #stop all running container
$ docker rm $(docker ps -aq) #remove all containers
$ docker rmi $(docker images -q) #remove all images
$ docker system prune #remove all stopped containers, all dangling images, all networks, all dangling build cache
$ docker system prune -a # remove all stopped container, all images, all networks, all build caches

Reference#

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