yoursite.conf

upstream balancer {
  server app01.yoursite.com:3500 weight=1 max_fails=3;
  server app02.yoursite.com:3500 weight=1 max_fails=3;
  server app03.yoursite.com:3500 weight=1 max_fails=3;
}

server {
  listen 80 default_server;

  # Location of our static files
  root /home/yoursite/public;

  # Static
  try_files $uri @app;

  location @app {
    proxy_redirect off;
    proxy_pass http://balancer;
    proxy_connect_timeout 75s;
    proxy_read_timeout 120s;
    proxy_send_timeout 120s;
    proxy_set_header   Host $host;
    proxy_set_header   X-Forwarded-For   $proxy_add_x_forwarded_for;
    proxy_set_header   X-Forwarded-Proto $scheme;
  }
}