Unbound - Shared Cache

[Tony Finch]

Talkabout <talk.about at gmx.de> wrote:
>
> Maybe a solution can be to integrate a Sub layer inbetween the local
> Cache and external resolvers, a shared Cache. This shared Cache is
> updated by all Peers when a query gets resolved and every peer can ask
> the shared Cache for entries when local Cache does not deliver any
> results. Shared Cache instances are then automatically synchronized.

You can do something a bit like your "sublayer" with dnsdist. You can
configure it with multiple back-end servers using a whashed or chashed
selection policy so that you aren't asking both back-ends to resolve all
questions.

https://dnsdist.org/guides/serverselection.html

The caveat is that "infrastructure" records (i.e. the delegation chain: NS
records, glue records, DS and DNSKEY records) have a big effect on DNS
performance and (unlike Unbound's shared cache) dnsdist won't help the
back-ends to avoid duplicating work resolving infrastructure records.


This discussion reminds me of Geoff Huston's investigation of zombie DNS
queries a few years ago http://www.potaroo.net/ispcol/2016-03/zombies.html
which made me wonder if some resolvers were using ill-advised hacks to
pre-heat cache B by sniffing the network for cache A's query traffic,
which is a great way to get a Sorcerer's Apprentice effect!

Tony.
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