I plan to balance load between my app servers using a separate Nginx server as a software load balancer. But actually, it's because a load balancer in front of the app servers allows me to update an app server (OS, application, etc.) when I want without downtime.
Then I realized, how do I update the load balancer itself? i.e. my site is still going to go down when I need to update the OS and Nginx on the server that acts as the load balancer for my application.
As hard load balancing is out of question, I was wondering if it's possible to connect two Nginx webservers together so that they balance load across app servers together, while enabling me to update one at a time, when I need to, without causing downtime.
Is this realistic?