One thing I observed today when double-checking the routing after we depooled Wikidough in esams was that eqiad took up all the redirected traffic, not drmrs as expected.
This led me to consider if we should perhaps think about allocating additional, region-specific, hostnames / IPs for the service. For example:
| Hostname | IPv4 | Announced from sites |
|---|---|---|
| europe.wikimedia-dns.org | 185.71.138.139 | esams, drmrs |
| north-america.wikimedia-dns.org | 185.71.138.140 | eqiad, codfw, ulsfo |
Users could use those instead if they wanted to ensure their requests only go to servers in the region. Beyond those suggestions I'd not be so sure. Certainly anything like that would make the logic about depooling harder, and I'm not sure it makes sense to publish a region-specific address if it is only going to be served by one POP (i.e. eqsin/magru).
Anyway just a thought, this kind of routing shouldn't really happen so much, but it can. I'm taking some inspiration here from how ntp.org have the generic pool names but also region-specific.