Is there an option to fallback to a default service subset?

Hi,
I’m trying to achieve zone awareness configuration (to avoid inter az costs).

Configuration:

  1. each worker has metadata with his AZ
  2. created service subset per AZ and one default service subset that contains all service az.
  3. route to the appropriate subset is done by HTTP POST.

That’s how I can query workers from a specific AZ/all AZs.

If all workers in the service subset are down, I want to be redirected to the default service subset instead I’m getting “no upstream available”.

Is there an option to config fallback to the default service subset?
Thank you!