title: Default domain with randomly redirect to multiple domains
body: <p>I'm using Nginx for reverse proxy. I'm thinking something is it possible to redirect to random domains. For example, I have several domains 
  mydomain.com 
  mydomain1.com 
  mydomain2.com 
  mydomain3.com 
  All domains are pointed to the same site which is hosted on one server. Is it possible when I request my default domain mydomain.com to choose randomly and redirect to one domain from the pool? I tried with rewrite rules, upstream balancing module also maps config with default domain and FastCGI or Lua to execute a shell script with random output string from an array. But no success.</p>
  
  <p>Thanks! :)</p>