[atlas] Long response times using one-off measurements with old probes

Hi,

I would like to point you to a discussion on the DNS-OARC mailing list:
https://lists.dns-oarc.net/pipermail/dns-operations/2018-December/018196.html

One of the operators at .ca noticed that old probes report way higher response times using DNS CHAOS queries (300% or more) (see also [3]).
After some digging, we came to the conclusion that this has to do with the fact that he is carrying out “one-off” measurements.
When carrying out the same query for a longer time, we cannot observe this delay.
The issues seems to be that one-off measurements are scheduled at probes using a different library than measurements that run for a longer period  (“eooqd” instead of “eperd”).

Some small additional delays have been documented before on the RIPE Atlas website and in research papers [1, 2], but the big delay with one off measurements was new to me.

Also to others? Is our assumption correct that the scheduler is the culprit?

Moritz

[1] https://dl.acm.org/citation.cfm?doid=2805789.2805796
[2] https://clarinet.u-strasbg.fr/~pelsser/publications/Holterbach-ripe-atlas-sharing-imc2015.pdf
[3] https://atlas.ripe.net/measurements/18086197/#!probes
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