[metrics-team] Sudden drop in obfs3 users on 2016-09-02

[David Fifield]

On Thu, Sep 22, 2016 at 12:03:17PM +0200, Karsten Loesing wrote:
> > Did something change recently in the way bridge users are counted, 
> > perhaps?
> 
> Not sure if this explains what we're seeing here, but something that
> did change on 2016-09-02 is that Tonga was shut down and Bifroest took
> over.
> 
> https://metrics.torproject.org/networksize.html
> 
> The effect was that suddenly ~40% of public bridges were turned into
> private bridges, in the sense that we're not learning any statistics
> from them anymore.  It might be that obfs3 bridges are
> disproportionately affected by that.

Thanks, I hadn't thought of that.

> > I checked that the 5 current default obfs3 bridges are running,
> > so that's not the problem.

Hmm, 2 of the 5 bridges (1 of 4 distinct fingerprints) are not running
this morning when I checked.

But in any case, none of the 5 default obfs3 bridges are reporting
statistics. None of these links works:

https://atlas.torproject.org/#details/A09D536DD1752D542E1FBB3C9CE4449D51298239 (LeifEricson)
https://atlas.torproject.org/#details/AF9F66B7B04F8FF6F32D455F05135250A16543C9 (Unnamed, formerly PacificSunset)
https://atlas.torproject.org/#details/1E05F577A0EC0213F971D81BF4D86A9E4E8229ED (ndnop0)
https://atlas.torproject.org/#details/4C331FA9B3D1D6D8FB0D8FBBF0C259C360D97E6A (ndnop2)

In comparison, 13/16 default obfs4 relays are findable on Atlas: all but
LeifEricson, ndnop3, and ndnop5.

Could the tonga–bifroest migration have caused these bridges to stop
reporting? If so, I'll make a new ticket and ask the operators to
upgrade or whatever they need to do to start reporting again.