title: How to make a HTTP call reaching all instances behind amazon AWS load balancer?
body: <p>I have a web app which runs behind Amazon AWS Elastic Load Balancer with 3 instances attached. The app has a <code>/refresh</code> endpoint to reload reference data. It need to be run whenever new data is available, which happens several times a week.</p>
  
  <p>What I have been doing is assigning public address to all instances, and do refresh independently (using <code>ec2-url/refresh</code>). I agree with <a href="https://stackoverflow.com/a/30976900/3953381">Michael's answer on a different topic</a>, EC2 instances behind ELB shouldn't allow direct public access. Now my problem is how can I make <code>elb-url/refresh</code> call reaching all instances behind the load balancer? </p>
  
  <p>And it would be nice if I can collect HTTP responses from multiple instances. But I don't mind doing the refresh blindly for now.</p>