What is the best practice to setup a 3 node web server loadbalancer and auto discovery?


We want to setup a cluster that will serve various websites( over 200 sites currently ) on Digital ocean with one floating IP. We have setup a continuous delivery and a clustered storage solution. The CD can create stacks to Rancher and upgrade them. The problem we are looking in to now is lb. What is the best practice way to lb 3 or more nodes with no manual configuration to create a new stack or upgrade them?

We also want to automate letsencrypt for the websites that requires it.