[metrics-team] Discontinuity on bridge numbers

[David Fifield]

On Mon, Jul 30, 2018 at 09:33:41PM +0200, Karsten Loesing wrote:
> On 2018-07-30 21:03, David Fifield wrote:
> > On Mon, Jul 30, 2018 at 08:34:52PM +0200, Karsten Loesing wrote:
> >> On 2018-07-30 19:55, David Fifield wrote:
> >>> On Mon, Jul 30, 2018 at 05:16:00PM +0000, nusenu wrote:
> >>>> Vinicius Fortuna [vee-NEE-see.oos]:
> >>>>> I noticed there's some discontinuity on the Bridge number data:
> >>>>> https://metrics.torproject.org/bridges-ipv6.html
> >>>>> https://metrics.torproject.org/networksize.html
> >>>>>
> >>>>> Do you know what happened there?
> >>>>
> >>>> the bridge authority got replaced, since this
> >>>> wasn't a smooth transition it resulted in a lot of
> >>>> lost bridges because they did not upgraded their tor version
> >>>> which contains the new bridge authority to pubish to.
> >>>
> >>> I think the new bridge authority is not the whole story, because the
> >>> bridge authority change happened on 2018-07-14, but the missing data
> >>> begins on 2018-07-07 (and ends on 2018-07-21).
> >>
> >> Hmm? What makes you think the gap ends on 2018-07-21? In the two graphs
> >> linked above the line comes back on 2018-07-13. Are you maybe looking at
> >> a cached version of those graphs? It took us a few days to import the
> >> new bridge descriptors into Tor Metrics, but AFAIK we did not miss any data.
> > 
> > I'm looking at
> > https://metrics.torproject.org/userstats-bridge-country.html (https://archive.is/AQ9Mh)
> > https://metrics.torproject.org/userstats-bridge-combined.html (https://archive.is/cQa3e)
> 
> Aha, indeed, those graphs have a larger gap than the two graphs linked
> above.
> 
> Here's what happened: the estimation algorithm gets confused by the
> sparse data it gets for the days between 2018-07-13 and 2018-07-20, so
> that it removes those dates from the plot.

Thank you for the references, everyone. I added them to the metrics
timeline.