It isn't obvious to me, from just looking at the the Google Load Balancer documentation if there is a simple way to configure a "site is under maintenance" or "site down" page.
Some cloud load balancers let you upload a simple html page and then offer a "checkbox" to serve that page until you uncheck it.
Or they let you upload a custom error page, and when the http health checks fail, they automatically serve that error page.
Is this easily done with the Google Cloud infrastructure?
I know we can edit our nginx configuration to serve such a page, but I'm looking for something a little more idiot proof, and something that will even work when nginx is down too.
(Not that we ever want to go down that much, but sometimes it happens, and it would be good to be able to post an intentional "yes, we know we are down - we'll be back up again soon".)
You can't do that in GCP for now.
See Google Cloud LB: Change "server error" default html page
And HTTP Load Balancer Custom Error Page
I needed to do that too. Unfortunately, there is no easy way, like a checkbox.