[atlas] Actual measurement interval much larger than planned

Hi Wenqin,

It may be because the probe is busy doing other things. We noticed a high interval between the scheduling and the actual measurement of one-off measurements on busy probes in http://conferences.sigcomm.org/imc/2015/papers/p437.pdf <http://conferences.sigcomm.org/imc/2015/papers/p437.pdf>

Cristel

> On Sep 1, 2016, at 7:14 PM, Wenqin SHAO <wenqin.shao at telecom-paristech.fr> wrote:
> 
> Dear list,
> 
> I encountered some cases where the actual time interval between two neighbouring measurements being much larger than the scheduled value.
> Have you witnessed similar cases? I appreciate explanations on underlying reasons.
> 
> Here goes an example:
> 
> from ripe.atlas.cousteau import AtlasResultsRequest
> filters = dict(msm_id=1010, probe_ids=[16981], start=1470055258, stop=1470056217)
> is_success, results = AtlasResultsRequest(**filters).create()
> if is_success:
>     for mes in results:
>         print mes.get('timestamp', -1)
> 
> The above code requests some built-in ping measurements (240s interval) made by probe 16981 and prints their timestamps. See below for the execution result:
> 
> 1470055259
> 1470055499
> 1470055978
> 1470056216
> 
> Four measurements are retrieved within the given time range.  I noticed that time interval between the 2nd and the 3rd measurement is 479s much larger than the planned value 240s.
> How come?
> 
> Many thanks for your attention.
> 
> Best regards,
> wenqin

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