[dnsdist] increase in drops or changed semantics?

[Remi Gacogne]

Hi,

On 10/7/19 10:47 PM, Christoph wrote:
> The output of topSlow() including the 'Rest' line covers only about 1%
> of the count shown in the 'Drops' counter so it is not related or is
> topSlow() only about recent-ish slow queries?

Yes, both topSlow() and grepq() are based on the queries and responses
present in the in-memory ring buffer, and we only keep up to N of them.
You can tune N by using the setRingBuffersSize() [1] directive, the
default being 10k. The drawbacks of doing so are a small increase in
memory usage and if you set it to a very large value that scanning the
ring buffer, for example to compute dynamic block rules, takes a bit longer.

> (there is no column description in the output, I assume the 3rd column
> is number of requests?)

Yes.

[1]:
https://dnsdist.org/reference/config.html?highlight=setring#setRingBuffersSize

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

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