Let’s say you’re setting up a load balancer for your instances in Amazon’s EC2. After you create your load balancer and assign it your instances, you may see on the Health Check tab “Out of Service”. The way you get rid of it is by clicking on the “Edit Health Check” link. Inside, you will see a Ping Path: input box. Here, you need to put a test page. Say test.html.
What Amazon does is pings this page. You cannot have redirects and it must return a 200 status code. Otherwise, Amazon will think that your service is down.