Mastering NGINX - Second Edition

Multiple upstream servers

It is also possible to configure NGINX to pass the request to more than one upstream server. This is done by declaring an upstream context, defining multiple servers, and referencing the upstream in a proxy_pass directive:

upstream app {

  server 127.0.0.1:9000;

  server 127.0.0.1:9001;

  server 127.0.0.1:9002;

}
server {

  location / {

    proxy_pass http://app;

  }

}

Using this configuration, NGINX will pass consecutive requests in a round-robin fashion to the three upstream servers. This is useful when an application can handle only one request at a time, and you'd like NGINX to handle the client communication so that none of the application servers get overloaded. The configuration is illustrated in the following diagram:

Other load-balancing ...