[metrics-team] Bringing back Tor Weather - volunteering developer

[Eran Sandler]

On Mon, 2018-07-23 at 09:41 +0200, Karsten Loesing wrote:
> 
> Okay, I'll try to give some more insights into these 2 hours that are
> mentioned several times on this thread, by giving two examples:
> 
> Imagine that a relay first drops out of the consensus with a valid-
> after
> time of 02:00 on any given day. Onionoo waits until some time between
> 02:15 and 02:20 to start its hourly update run. The reason for
> waiting
> 15 to 20 minutes is that it needs the most recent consensus, but also
> the newly sanitized bridge descriptors as input. Onionoo then runs
> until
> about 02:45 to 02:50, and Weather can learn about changes to the
> network
> shortly after. That's a delay of a bit under 1 hour.
> 
> Now, where do the 2 hours come from? Imagine that a relay goes
> offline
> at 00:51 on that day. The directory authorities had just included it
> as
> running in their votes that they exchange at 00:50 and altogether
> will
> include it in their consensus with valid-after time 01:00. Now it's
> going to take until 01:50 before they vote again and not list that
> relay
> anymore in the 02:00 consensus. Altogether, that's a delay of roughly
> 2
> hours between the relay going down and Weather notifying the
> operator.
> 
> All in all, the fact that directory authorities vote once per hour
> and
> take 10 minutes for that vote process contributes between 10 minutes
> and
> 70 minutes to the delay, and Onionoo adds another 50 minutes.
> 
> There's not much we can do in Onionoo to further reduce this delay.
> We
> could maybe save another 10 or 20 minutes by parallelizing things
> more.
> But that's easier said than done, and at the moment it's not a
> priority
> for the metrics team.

Thanks for the details explanation.

I assume that sending a request with type=realy&running=false will
return all currently non-active relays. How long are these relays
returned in this result?

For example, say I have a relay and its working, so I got it back on
type=relay&running=true. After a couple of days it stopped working. At
some point in the election process it will be marked as dead and it
should appear when doing an API call to onionoo with
type=realy&running=false. How long will that specific node stay there? 

Thanks,
Eran
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