3 ms·
I wrote this as a pure joke, but now that I learned that SERVFAIL is not cached on browsers, clients, intermediate DNS servers [0] etc. I am curiously wondering
by littlecranky67 5y ago
I wrote this as a pure joke, but now that I learned that SERVFAIL is not cached on browsers, clients, intermediate DNS servers [0] etc. I am curiously wondering what will be going on. It is not only FB apps, it is basically every website request (that uses FB JS for ads, tracking, etc.) that triggers a DNS request, which will be forwarded 1:1 from the ISP's DNS to the null-routed FB Subnet. This should put orders of magnitude more load on resolving DNS servers than usual.
[0]: https://serverfault.com/questions/479367/how-long-a-dns-timeout-is-cached-for https://serverfault.com/questions/479367/how-long-a-dns-time...
- bowaggoner 5y agoI enjoyed the comment. You might like my short story along the same lines from a few years ago: https://bowaggoner.com/writeups/robust.html https://bowaggoner.com/writeups/robust.html
- pomian 5y agoVery fun little story. Thanks for writing it.
- yourad_io 5y ago> but now that I learned that SERVFAIL is not cached on [...] intermediate DNS servers [0] I thought so too, but at least some do cache according to Cloudflare's blog post: > Consequently, 1.1.1.1, 8.8.8.8, and other major public DNS resolvers started issuing (and caching) SERVFAIL responses. https://blog.cloudflare.com/october-2021-facebook-outage/ https://blog.cloudflare.com/october-2021-facebook-outage/
- im3w1l 5y agoFacebook is so large that even caching the SERVFAIL with a TTL measured in seconds should cut down a lot of traffic.
- daper 5y agoAs I understand my favorite resolver - unbound - has separate "infra" cache that also caches RTT times, and "down" status of name servers: https://nlnetlabs.nl/documentation/unbound/unbound.conf/#infra-keep-probing https://nlnetlabs.nl/documentation/unbound/unbound.conf/#inf...