AWS load balancer and maintenance page
I'm using AWS Load Balancer with 3 EC2 servers, and I'm trying to serve a Maintenance page when site is under maintenance.
This page need to return 503 HTTP code, because it is a proper code for a maintenance mode and will prevent possible problems with SEO.
When I return 503 code from any of my servers, Load Balancer makes it "Not In Service", and when all servers return 503, website returns a blank page (because all servers are disconnected).
My questions are:
1) Is there any way to serve a custom static page with a message for visitors from Load balancer if there is no healthy servers?
2) Or how to configure Load Balancer's Health Check that it will not consider 503 as a reason to mark server as "unhealthy"?
Thanks!
Answer
You could implement an additional route in your app server, let's say /hcm (for health check maintenance), that always responds 200 OK. When it's time for maintenance, you programmatically modify the ELB health check to use the /hcm target which returns 200 OK rather than / or /index.html, which both return 503 Service Unavailable. Revert these changes when exiting maintenance.