[dns-operations] More Aggressive prefetch for popular names

bert hubert bert.hubert at powerdns.com
Sat Apr 6 15:02:24 UTC 2019

On Fri, Apr 05, 2019 at 09:19:27AM +0800, Davey Song(宋林健) wrote:
> I’m writing to ask if any resolver operator is doing or be asked to do
> aggressive pre-fetch for popular names in the case of urgent changes of
> owners’ names. 

So why would anyone want to prefetch popular names? You get a lot of hits
already while the TTL expires. Preventing that one cache miss does not get
you a lot of gain on aggregate. It appears that the benefit of prefetching
is concentrated among 'moderately popular domains'. 

If a popular name with a low TTL has a slow / unreliable set of
authoritative servers, why paper over that? They can either raise their TTL
or fix their servers.

In general, I don't think resolvers should be bending over backwards to fix
suboptimal authoritative server configurations.

Also, users can definitely deal with a 10 millisecond cache miss.

Writing a correct resolver is already super hard. The recent 'windows
update' outage showed that doing prefetching is not easy.


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