Xdebug with a load balanced site: How to debug?

I have a local site that is load balanced, so the single main domain sends incoming web traffic to 2 other sites to balance the load.

QUESTION: How to get xdebug to stop on break points?

If I access site.test via a web browser the response comes from either app20.site.test or app30.site.test back through the main site.  What im unclear on is how to setup the debugger to stop.

xdebug works and stops on a site without this setup but won't stop using this setup.  I think the issue could be that the SERVER settings does not have a single “Absolute Path On The Server” setting.

I've tried a few different variations of the absolute path and the ‘host’ and the SFTP host setup but have yet to find one that allows the debugger to stop.

The main domain isn't really used because the traffic is directed but I tried setting that up as a server anyhow, but as expected it fails.