title: Single fault tolerant machine with amazon AWS
body: <p>For a particular service, I need to run a <strong>single</strong> EC2 instance in a fault tolerant way. </p>
  
  <p><strong>Only in case of errors</strong> I want that the "primary" machine is terminated and the traffic must be be redirected on "secondary" machine <strong>within some seconds and automatically</strong>.
  This is the classic case of a primary and secondary server with the constraint that the secondary server must not work unless the primary crashed.</p>
  
  <p>I'm quite new in this world but as far as I understood, with Elastic IP I need to manually change the binding if the primary machine hangs.
  Instead, with Auto Scaling, ELB and CloudWatch I can:</p>
  
  <ul>
  <li>Set up an auto scaling park with 2 machine, but the traffic will be load balanced (sticky sessions is not what I want because I need <em>all</em> the traffic on the primary machine if it works)</li>
  <li>Set up an auto scaling with just 1 machine, so if the primary machine hangs automatically a new one will be online. However as far as I know the boot process needs several minutes.</li>
  </ul>
  
  <p>Any advice on how I can combine AWS services to achieve this goal?</p>