On 2/15/19 5:39 PM, Nico wrote:
> If it helps, at the same time the metrics for "cache deferred lookups
> per poool" and "cache deferred
> inserts per pool"  incremented proportionally.

I think you have your answer right there, the contention between thread
is too high and by default dnsdist gives up if the cache is already
locked by another thread when it tries to access it.
I would suggest increasing the number of shards to a sensible value (try
50 for a start, for example), see the 'numberOfShards' parameter of
newPacketCache() [1]. You could also try to instruct dnsdist to wait for
the lock when it is trying to insert a new response, instead of giving
up, setting 'deferrableInsertLock' to false. But I'm pretty sure you
won't need it with enough shards.

[1]: https://dnsdist.org/reference/config.html#newPacketCache

Best regards,
Remi Gacogne
PowerDNS.COM BV - https://www.powerdns.com/

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