pre heat cache

[Tony Finch]

> On 18 Feb 2016, at 18:59, Robert Edmonds <edmonds at mycre.ws> wrote:
> 
> A large proportion of records are only ever used "once, or a handful of times", according to researchers: [...]

Yes, and there's an amazing amount of crap in the cache too. About 14% of our cache is weird Sonicwall geoip records, which are probably only used once but have a 1week TTL. Sigh! They are relatively fast to re-query, though. (I wonder if this screws up Sonicwall's stats...)

> If there were some way to only dump the most popular records from the cache (say the top 1,000 or 10,000), it would probably speed up the pre-heating process significantly and still warm the cache to an acceptable degree.

Yes, that would be cool.

There's also a performance problem somewhere in adns-masterfile - it can only manage about 5000 qps before running out of CPU; I have done over 20000 qps with adns before (querying the Alexa top-1m list) so it ought to be possible to go a lot faster.

> Does rndc dumpdb dump the cache in DNS tree order, or could it be convinced to follow the LRU order?

At the moment it is DNS tree order.

Tony.
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