Run Docker Container using Nginx Load balancer

In this article, we will create node js file and run the file on two docker instance using Nginx load balancer.

Make a directory

To make a directory type:

$ mkdir devops
$ ls 

Output: devops

So we can see that a directory called devops has been created

Now enter into the directory and create a index.js file which respond to HTTP request.. To open the index file:

$ vim index.js 

Let’s paste below code into the index file

Code:

var http = require('http');
var fs = require('fs');

http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/html'});
  res.end(`<h1>${process.env.MESSAGE}</h1>`);
}).listen(8080);

Dockerizing the index file

To dockerize the index file. We should open a file name Dockerfile in our devops directory.

$ touch Dockerfile 

Dockerfile has been created. Now, we need to write below contents to build docker image:

FROM node
RUN mkdir -p /usr/src/app/
COPY index.js /usr/src/app
EXPOSE 8080
CMD ["node", "/usr/src/app/index.js"]

Here, FROM: Firstly, It is used to pull node image from docker hub which is fit with our application language.
RUN mkdir: Secondly, This defines my working directory.
COPY : It helps to copy my source codes into /usr/src/app directory .
EXPOSE: Thirdly, Our application will be run in an isolated container. So, there is only way to reach into the container by listening a port. EXPOSE helps us to do so at he port 8080 port.
CMD: Finally , our application is ready to run. CMD uses to launch the application locally.

Now type:

docker build -t firstproject .

Output:

So, our docker image has been created. Now, we have to create two container. To do this write below command:

docker run -e "MESSAGE=Hello I am your first node!!!" -p 80:8080 -d firstproject 

docker run -e "MESSAGE=Hello I am node” two -p 80:8080 -d firstproject 

Output: 

Here it is !! Our container is running. Next step, we will use Nginx for dockerized container for load balancing. First make a directory

$ mkdir nginx

Create a file called nginx.conf

$ touch nginx.conf
$ vim nginx.conf

Write the below contents:

upstream first-project {
    server 172.17.0.1:80 weight=1;
    server 172.17.0.1:81 weight=1;
}

server {
    location / {
        proxy_pass http://first-project;
    }
}

Here, upstream module used to define group of servers containing urls of our application. We will use default round robin algorithm to load balance with nginx.

Now, we will write a docker file to dockerized the nginx container.

$ touch Dockerfile 
$ vim Dockerfile 

Now , write the below content in this file :

FROM nginx
RUN rm /etc/nginx/conf.d/default.conf
COPY nginx.conf /etc/nginx/conf.d/default.conf

We can run the nginx container

$ docker run -p 8080:80 -d nginx-container

If we hit the enter after writing http:/localhost:8080/ , we will see on of our containers well be running. If we reload the browser every time message will be changed. That means, nginx sending traffics to both container using round robin algorithm.