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

[Karsten Loesing]

On 2018-07-23 20:23, Eran Sandler wrote:
> 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? 

That relay would stay there for 1 week and then disappear. Its history
in terms of "first_seen" and its graphs will remain on the Onionoo
server for whenever the relay returns. But after that week it won't be
listed in responses anymore.

> Thanks,
> Eran

All the best,
Karsten

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