NGINX: NGINX config for Level 7 proxy

http {
    
    upstream allbackend {
        #ip_hash;
        server 127.0.0.1:2222;
        server 127.0.0.1:3333;
        server 127.0.0.1:4444;
        server 127.0.0.1:5555;
    }
    
    upstream app1backend {
        server 127.0.0.1:2222;
        server 127.0.0.1:3333;
    }

    upstream app2backend {
        server 127.0.0.1:4444;
        server 127.0.0.1:5555;
    }

    server {
          listen 80;
          location / {

              proxy_pass http://allbackend/;
           }

         location /app1 { 
              proxy_pass http://app1backend/;
          }
        
        location /app2 {
              proxy_pass http://app2backend/;
         }
         
        location /admin {
          return 403;
        }          
     }

}

events { } 

1. HTTP Block

http {
    ...
}

The http block is the main container for HTTP server settings. All configurations related to serving HTTP requests (such as reverse proxying, load balancing, etc.) are inside this block.

2. Upstream Servers

In Nginx, an upstream is used to define a group of backend servers. Nginx can distribute requests to these servers, which helps with load balancing.

upstream allbackend

upstream allbackend {
    server 127.0.0.1:2222;
    server 127.0.0.1:3333;
    server 127.0.0.1:4444;
    server 127.0.0.1:5555;
}

This defines a set of backend servers that Nginx will proxy traffic to. In this case, there are four servers running on the same machine (localhost, 127.0.0.1) but on different ports (2222, 3333, 4444, and 5555).

• ip_hash (commented out) is an optional directive that would make sure requests from the same client (IP) are always sent to the same backend server. This is useful for session persistence, but it’s not enabled in this config since it’s commented out.

upstream app1backend

upstream app1backend {
    server 127.0.0.1:2222;
    server 127.0.0.1:3333;
}

This upstream defines a group of two backend servers for “app1”, running on ports 2222 and 3333.

upstream app2backend

upstream app2backend {
    server 127.0.0.1:4444;
    server 127.0.0.1:5555;
}

This upstream defines a group of two backend servers for “app2”, running on ports 4444 and 5555.

3. Server Block

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

    location /app1 {
        proxy_pass http://app1backend/;
    }

    location /app2 {
        proxy_pass http://app2backend/;
    }

    location /admin {
        return 403;
    }
}

• listen 80: This configures the server to listen on port 80, the default HTTP port.
• location /: This defines how to handle requests to the root of the website (/):
  • Requests to the root (e.g., http://yourdomain.com/) will be forwarded to the upstream allbackend. This means the request will be passed to one of the backend servers defined in the allbackend upstream block (ports 2222, 3333, 4444, 5555).
• location /app1: This handles requests to /app1:
  • Requests to http://yourdomain.com/app1 will be forwarded to one of the backend servers defined in the app1backend upstream block (ports 2222, 3333).
• location /app2: This handles requests to /app2:
  • Requests to http://yourdomain.com/app2 will be forwarded to one of the backend servers defined in the app2backend upstream block (ports 4444, 5555).
• location /admin: This handles requests to /admin:
  • Requests to http://yourdomain.com/admin will receive a 403 Forbidden error. This is often used to block access to sensitive areas of a site, such as an admin panel.

4. Events Block

events { }

This block is used to configure event-related settings in Nginx, such as worker processes. In this case, it’s empty, meaning it will use the default settings.

Summary of How it Works:

• Load balancing: Nginx will balance requests across multiple backend servers using the upstream directives.
• Root and application-specific routing:
  • The root (/) routes traffic to a larger pool of backend servers (allbackend).
  • The /app1 and /app2 locations route traffic to separate pools of backend servers (app1backend and app2backend respectively).
  • Access to /admin is blocked with a 403 Forbidden response.

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