block4.

# http context
    upstream backend_hosts {
      least_conn;
      server host1.example.com;
      server host2.example.com;
      server host3.example.com;
    }
    
    # next we set up our server
    server {
      listen 80;
      server_name example.com;
      location /proxy-me {
        proxy_pass http://backend_hosts;
      }
    }