Least connected load balancing

While the default load balancing algorithm is round-robin, it doesn't take into consideration either the server load or the response times. With the least connected method, we distribute connections to the upstream server with the least number of active connections.

Getting ready

To test the load balancing, you'll need to be able to run multiple versions of your app, each on different ports.

How to do it...

The upstream block directive looks exactly the same as the round-robin configuration, except we now explicitly tell NGINX to use the least connected method—a reminder that this needs to remain outside of the server block directive. Here's our upstream block:

upstream localapp { 
    least_conn; 
 
    server 127.0.0.1:8080; 
    server 127.0.0.1:8081; 
    server 127.0.0.1:8082; 
} 

Then, we'll define our server block directive:

server { 
    listen       80; 
    server_name  load.nginxcookbook.com; 
    access_log  /var/log/nginx/load-access.log  combined; 
...