Minecraft can read a special DNS record type called SRV records. You can create a record like that to point Minecraft to a port that the server is running on. It doesn’t even have to have the same ip as the webserver.

This is for Namecheap, but the general principle applies everywhere: https://www.namecheap.com/support/knowledgebase/article.aspx/9765/2208/how-can-i-link-my-domain-name-to-a-minecraft-server/

If you’re willing to go the extra mile for OpenStack, I suggest you check out OKD and its virtualization operator. It’s much easier to install and maintain, too