How to Create an NGINX Load Balancer for Two Web Servers in Docker?| S-Logix

How to Create an NGINX Load Balancer for Two Web Servers in Docker?

Condition for Create an NGINX Load Balancer for Two Web Servers in Docker

Description:
In this task, you will:
Run two separate NGINX containers (app1 and app2)
Create a custom NGINX load balancer container
Configure load balancing so that each browser refresh alternates between the two applications
This demonstrates how NGINX acts as a reverse proxy and load balancer inside Docker.

Steps

Step 1: Create a Working Folder
Description: Create a project directory where configuration files will be stored.
Command:
```
mkdir nginx-load-balancer
cd nginx-load-balancer
            
```

Step 2: Run Two Web Server Containers
Description: Start two independent NGINX containers that will act as backend servers.
Commands:

docker run -d --name app1 nginx
docker run -d --name app2 nginx

Container	Command to set response
For APP1	docker exec -it app1 bash echo "<h1>This is APP1</h1>" > /usr/share/nginx/html/index.html exit
For APP2	docker exec -it app2 bash echo "<h1>This is APP2</h1>" > /usr/share/nginx/html/index.html exit

Step 3: Create nginx.conf (Load Balancer Configuration)
Description: Create a custom config file that forwards requests to both containers.
Command:

nano nginx.conf

Paste the following:

events {}
http {
    upstream myapp {
        server app1:80;
        server app2:80;
    }

    server {
        listen 80;
        location / {
            proxy_pass http://myapp;
        }
    }
}

Save → CTRL + O → Enter → CTRL + X

Step 4: Run the NGINX Load Balancer Container
Description: Start a new NGINX container that uses your custom configuration and connects to both backend apps.
Command:
```
docker run -d --name load-balancer --link app1 --link app2 -p 8093:80 -v $(pwd)/nginx.conf:/etc/nginx/nginx.conf nginx
            
```
✔ --link makes app1 & app2 reachable
✔ -v mounts custom config
✔ Port mapping: 8093 → 80
Step 5: Test the Load Balancer
Description: Access the container in the browser and refresh multiple times.
Open:
http://localhost:8093

➡ You should see alternating responses:
This is APP1
This is APP2
This is APP1
This is APP2