Gcore authoritative DNS was impaired for ~33 minutes
14.11.2022 19:53 (UTC) authoritative resolving has failed on a server in Turkey
14.11.2022 19:58 (UTC) a first monitoring alert about the DNS issue received
14.11.2022 20:02 (UTC) on-call engineer started work on the incident together with the DNS core team
14.11.2022 20:18 (UTC) team identified a cause
14.11.2022 20:26 (UTC) workaround applied: all DNS servers have been switched to the backup DNS zones propagation scheme
15.11.2022 13:59 (UTC) cache consistency was repaired, switched back to the primary delivery scheme
customer filed a ticket that uppercase records were not working
we decided to fix it by storing the records as lowercased
as we use redis as a changes propagation system and it is case sensitive. We’ve duplicated all the keys at this point ( one with upper case and one with down case ). Then we purged the upper case duplicates which also triggered invalidating a dns service cache.
DNS server cache was managed in case-insensitive way. So we purged both ( upper and lower cased ) keys.