The goal of this lab is to combine everything that you have learned in the previous labs and put it into practice.
Your goal is to create your own Docker image that contains a "Hello world!" application in a javascript.
Once you have created it, push it to the Docker Hub and share it over Slack so you colleagues can check what you have created.
Because the username of your dockerhub account is used in this exercise start with exporting it into an environment variable like in a previous lab.
export DOCKER_HUB_USERNAME=<YOUR_DOCKER_HUB_USERNAME>
First start with a new folder on your laptop. We will put everything for the application in this folder.
You can follow the following steps to create a simple HelloWorld javascript application. Be free to use your own imagination in creating this application.
Start with a package.json file with the following content.
{
"name": "docker_web_app",
"version": "1.0.0",
"description": "Node.js on Docker",
"author": "First Last <[email protected]>",
"main": "server.js",
"scripts": {
"start": "node server.js"
},
"dependencies": {
"express": "^4.16.1"
}
}
After you created this package.json file run npm install. You wil probably
get the following output.
Command 'npm' not found, but can be installed with:
sudo apt install npm
This is because npm is not installed on this machine so you will have to run
the following command before you do the npm install command.
sudo apt install -y npm
Now create your server.js file with the following content.
'use strict';
const express = require('express');
// Constants
const PORT = 8080;
const HOST = '0.0.0.0';
// App
const app = express();
app.get('/', (req, res) => {
res.send('Hello world\n');
});
app.listen(PORT, HOST);
console.log(`Running on http://${HOST}:${PORT}`);
Now that we have an application let's put in in a container!
Start with creating a Dockerfile in the same folder as where you created the
javascript files. As usual don't give this file an extension.
Let's start with how our Dockerfile should be build up. First we will need to
define a docker image where we are going to build on.
FROM node:8
We will choose the node image and continue from there. We need to create a work directory inside of the container.
WORKDIR /usr/src/app
Copy our package.json file in the container. We will use a wildcard to be sure
that all the files are copied. (after npm version 5 a package-lock.json file is
also created next to the package.json file. )
COPY package*.json ./
You can now use the npm install in the Dockerfile
RUN npm install
Now copy all your application source in the container with the following COPY.
COPY . .
Since we are using port 8080 inside of the container, this is explained in lab
lab-04, we need to expose the port in the Dockerfile.
EXPOSE 8080
The only thing that's left is defining our ENTRYPOINT this is the behaviour of
the container when it will start. It needs to be the npm start command in this
case.
ENTRYPOINT [ "npm", "start" ]
It will start the server and serve our service on port 8080 inside the
container. Your entire Dockerfile should look something like this.
FROM node:8
WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 8080
ENTRYPOINT [ "npm", "start" ]
Let's build this image.
docker build -t ${DOCKER_HUB_USERNAME}/hello-javascript .
Now that we have our image we will be able to run this with Docker. Also seen in lab-04, you will have to map the 8080 port on the 8080 port on your system. This is done in the docker run command.
docker run -p 8080:8080 ${DOCKER_HUB_USERNAME}/hello-javascript
> [email protected] start /usr/src/app
> node server.js
Running on http://0.0.0.0:8080
When you get the output above your server is running on localhost. Verify by
browsing to localhost:8080.
Congratulations you created your own Javascript application inside of a docker container.
To clean up run the following commands:
docker system prune
unset DOCKER_HUB_USERNAME