[c-nsp] Cache DNS servers

[Nathan Ward]

> On 2/12/2015, at 15:23, Roland Dobbins <rdobbins at arbor.net> wrote:
> 
> On 2 Dec 2015, at 3:28, sthaug at nethelp.no wrote:
> 
>> But simply replacing BIND with something else is *not* likely to solve
>> your problem.
> 
> Concur 100%.
> 
> You may also wish to consider two layers of caching - e.g., an aggregate cache in addition to caching on user-facing caches, along with dedicated resolvers.  See this .jpg diagram:
> 
> <https://app.box.com/s/72bccbac1636714eb611>

I have tested similar topologies in anger and haven’t found that the benefit (which is fairly small) is worth it for the added complexity.

I find that unbound with large cache sizes works very well - https://www.unbound.net/documentation/howto_optimise.html <https://www.unbound.net/documentation/howto_optimise.html> is a good primer.

I collect stats with collectd and the unbound collectd python module from here:
https://github.com/tarnfeld/collectd-unbound <https://github.com/tarnfeld/collectd-unbound>

We get the stats out the end of our stats pipeline with Grafana, and have a detailed analytics dashboard that give us hints about what needs to be looked at. We chart queries per CPU%, recursion times, all sorts of good stuff.

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Nathan Ward