title: Check Service IIS down on nginx load balancing using NGINX
body: <p>I setup load balancing with nginx.
  Here is my config</p>
  
  <pre><code>upstream mywebsite1  {
    least_conn;;
    server xxx.xxx.xxx.20 weight=1 max_fails=3 fail_timeout=15s;
    server xxx.xxx.xxx.21 weight=1 max_fails=3 fail_timeout=15s;
  }
  </code></pre>
  
  <p>Default all request sent to 2 sever backend. Now if IIS Service in Backend1 (xxx.xxx.xxx.20) down, Access to website will be interrupted. So how can make all request auto connect to backend2 when IIS service on backend1 down, or connect to backend1 when IIS service on backend2 down ???</p>
  
  <p>Thanks!</p>