Sounds like a reasonable feature.

/assign @jukie

jukie is not allowed to assign users.

I'll work on this

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/remove-lifecycle stale

This might only be applicable when force_locality_direct_routing (#38756) is enabled as a protection mechanism to avoid overloading the local zone.

Stepping through the code I think Envoy would already self-protect small zones. For example consider the below structure:

  // Zone A: 1 local (33.33% local_percentage), 2 upstream hosts (20% upstream_percentage)
  // Zone B: 1 local (33.33% local_percentage), 4 upstream hosts (40% upstream_percentage)
  // Zone C: 1 local (33.33% local_percentage), 4 upstream hosts (40% upstream_percentage)

For zone A local > upstream which means it'd fallback to residual correct?

So then it steps down and determines what percentage can be routed locally which would be ~60% in this case (20/33.33).

Assuming each zone has 100 request inbound the result should be:

Zone A - 60 requests from local, 0 cross-zone
Zone B - 100 requests from local, 20 cross-zone
Zone C - 100 requests from local, 20 cross-zone

Which already achieves equal distribution and provides protections to smaller zones. I'll plan on just adding this as an extra gate to force_locality_direct_routing but I wanted to first ask if there's additional use cases for min_zone_size to consider. @KBaichoo does the above sound correct?