[Pdns-dev] feature request (persistent cache for recursor)

Igor Popov igorpopov at newmail.ru
Wed Apr 25 10:22:55 CEST 2007

> I run a cluster of recursors behind a loadbalancer and while its true what
> you say, performance of the recursor is much better with a full cache, i
> don't really seem to have a need for that feature as my caches tend to get
> filled up again rather quickly and i never saw any significant performance
> impact on our caching dns performance due to recursor restarts.
> I wonder what your cache size might be to let you feel any performance
> impacts, mine range from 1 to 2 million entries.
> Also implementing something like what you proposed bears the problem that
> by the time you load the cache from a file its TTLs will already be
> outdated and thus you end up serving old and probably even bogus data which
> i think was the reason i was told BIND does not incorporate that function.

I have two running recursors, the first one is limited to 2 million and 1 
million for the second.
After recursor is started negative cache becames too big until 150000-20000 
entries hit in the cache.

Powerdns is written in c++ with stl, I think it is possible to write memory 
allocator that uses mmap and use this allocator for cache. Current TTL of 
every record should be stored with record and whole dump should store 
timestamp when it was created or mtime can be used.

He had occasional flashes of silence that made his conversation
perfectly delightful.
		-- Sydney Smith

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