如何在不为特定域提供服务的情况下向Apache发送特定域的请求？

Question

I have an AWS EC2 server that hosts 3 domains with Apache 2. This server sits behind an AWS ELB load balancer which sends it requests. If I want to update this server, instead of taking the server down, I can create a new identical EC2 server and install all the software using the same scripts that built the first server and when it is ready I can add the new server to the ELB and then remove the old server. This gives me zero downtime which is great.

But before I remove the old server how do test the new server to prove everything is working and it is serving those 3 domains? DNS points to the ELB for these domains, the ELB sendsthe requests to the server, and the Apache install on the server routes the traffic to the appropriate site depending on what subdomain was requested. Is there a way make a request to the new server via IP address since that is the only way to address it before it is behind the ELB but tell it I want to make a request to a specific subdomain? If not how else can I prove all 3 sites are running and working properly without just adding it to the ELB, removing the old server, and crossing my fingers?

PS Sorry for the poor title. Please edit it if you can think of a better one that better represents what I am asking.

Answer 1

Use ELB healthcheck to perform the check. I recommend you to enable Apache server status mod. Use health check against /server-status and if it returns 200 for certain period of time, ELB will mark the instance as active and healthy.