On: Why is DNS still hard to learn?

[Dylan16807]

"I didn't know that cache existed" isn't because of the difficulty of invalidating the right items, though.

And the occasional cache that keeps things forever is so extra broken that it's not doing that because cache invalidation is hard, it's either a supreme misunderstanding or it's incompetence.

[lanstin → Dylan16807]

Sadly reboot the VM is still a valid step in debugging DNS, while you google "clear cache for this type of client resolver"

Also, the dreaded caching of negative results/authoritative no such domain just before you get the new domain working properly.

[zhengyi13 → Dylan16807]

> And the occasional cache that keeps things forever is so extra broken that it's not doing that because cache invalidation is hard, it's either a supreme misunderstanding or it's incompetence.

Working in phone technical support in the early 2000s, I encountered first in CF6 and then at least one J2EE implementation (Websphere, maybe?) where the $^&#ing default was to cache DNS results forever.

The behavior was borderline undocumented, and the setting to fix it was even less well documented. It's like they wanted DNS to not be a thing.