[dnsdist] Latency value under showServers()

[bert hubert]

On Mon, Mar 19, 2018 at 11:30:08AM +0000, Nigel H wrote:
> I'm seeing a discrepancy when i run showServers() in dnsdist.  Our internal
> pool of dns servers appears correct and monitoring shows the odd spike in
> latency but our external pool (opendns) seems to just keep increasing in
> value.  The documentation states its the latency for this servers in
> milliseconds but when I test using dig I'm seeing normal resolution times
> 1-8ms mostly but dnsdist reports latency like below (27ms).

Hi Nigel,

The likely reason for the increase is that opendns has only received 169 and
148 queries so far.  This means the weighted average latency still includes
a lot of 0.

Eventually, you should see the opendns latency plateau. 

With 'grepq()' you should be able to find the queries being sent to opendns,
and how long dnsdist thought they were taking.

You could then perhaps retry those queries with 'dig' to see how long they
take. 27ms is not unreasonable for mostly cache misses.

> Can someone confirm its meaning?  Is it an average latency based an amount
> of queries to this server or is it the highest latency seen?  Also does
> dnsdist incorporate the latency of the health check?

The last part, no. First part, it is average.

	Bert