[dns-operations] prefetching and thundering herds
dot at dotat.at
Wed Jul 15 21:15:04 UTC 2020
Mark Delany <b9w at charlie.emu.st> wrote:
> But in terms of thundering herds, it's still seem no worse than if none of the stub
> resolvers cached.
> However, I can see how if the choice is between stub caches which "smear" TTL (regardless
> of mechanism) and stubs which don't "smear", the smearers are probably a little nicer to
> recursive resolvers which incur high costs queuing duplicate queries.
> But then I have to wonder, is there a fundamental reason why recursive
> resolvers perform non-linearly as the arrival rate of identical queries
It's the bimodal behaviour between cache hits and misses, and the higher
the query rate the more queries arrive while the cache is being refilled.
I think it only gets nonlinear if the recursive server's query
deduplication is nonlinear.
I was probably wrong to worry about thundering herds - I was thinking
about them because I started wondering about synchronized cache expiry in
a somewhat different context. Then I noticed that stub caches might stymie
f.anthony.n.finch <dot at dotat.at> http://dotat.at/
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