When the application is not reachable because of an upgrade can you force people to logout of your application? Because right now when people are still working and you put your application offline the users get some random errors.

What i want is an AppOffline page or something. I want to create a under construction page which will only be displayed when the application is not reachable, instead of the login screen when you fill out your credentials and you will get a message something like “Application is not reachable”