Change Details

With the ATS clusters ready to serve production traffic (T207048), the next step is to serve a portion of the cache_upload requests via ATS and observe its behavior. To do that, we need to: * add a feature flag to point individual Varnish frontends in core DCs to their dc-local ATS clusters * flip the switch on one cache_upload frontend in eqiad and one in codfw * observe and document any issues, gather operational experience * switch back to Varnish

With the ATS clusters ready to serve production traffic (T207048), the next step is to serve a portion of the cache_upload requests via ATS and observe its behavior. To do that, we need to: * add a feature flag to point individual Varnish frontends in core DCs to their dc-local ATS clusters * flip the switch on some cache_upload frontends, both in eqiad and codfw * observe and document any issues, gather operational experience * switch back to Varnish

With the ATS clusters ready to serve production traffic (T207048), the next step is to serve a portion of the cache_upload requests via ATS and observe its behavior. To do that, we need to: * add a feature flag to point individual Varnish frontends in core DCs to their dc-local ATS clusters * flip the switch on onsome cache_upload frontends, both in eqiad and one in codfw * observe and document any issues, gather operational experience * switch back to Varnish