title: about ip_hash in nginx upstream module
body: <p>I want to replace pound with nginx as loadbalancer and all tests look fine so far. I will do a typical upstream configuration like this:</p>
  
  <pre><code>upstream backend {
    ip_hash;
    server   backend1.example.com;
    server   backend2.example.com;
    server   backend3.example.com;
  }
  </code></pre>
  
  <p>There are now 2 questions left open:</p>
  
  <ol>
  <li>How long does this stickyness last? Is there a ttl to be defined somewhere?</li>
  <li>Does the stickyness survive restarts and/or reloads of nginx?</li>
  </ol>
  
  <p>I could not find the answer in the nginx wiki. Links to official docs are welcome.</p>