Re: [tor-relays] Tor Weather : Node-Flag [Guard] Alert

[Roger Dingledine <arma@xxxxxxxxxxxxxx>]

On Tue, Sep 26, 2023 at 07:44:29PM -0400, denny.obreham@xxxxxxxxxxxxxxxxx wrote:
> I received the following message from Tor Weather. According to Tor Metrics, this exit relay still has no Guard flag.
> 
> Another - slightly more recent - exit relay (25FC41154DCB2CAE3ABD74A8DFCD5B90D2CFFD57) is on the same server and IP,
> and still has the Guard flag (although with 0% guard probability).
> 
> Should I do something with this info?
> 
[...]
> > We have detected that the node - 3B85067588C3F017D5CCF7D8F65B5881B7D4C97C associated
> > with your subscription has lost the Guard flag
> > for more than 1hr(s). This may impact the performance of your service.

Thanks for running relays!

The low-complexity answer: no, don't worry about it. The Guard flag
doesn't really matter for exit relays these days, because the bottleneck
in the Tor network is exit capacity, so clients won't be using exit
relays for their first hop anyway. And even if they weren't exit relays,
I would also say don't worry about it -- run your relays, enjoy feeling
good that you're contributing, and don't feel like you need to be gamified
into collecting all the flags like pokemon.

The medium-complexity answer: you can check out the
individual votes about your relay by going to the bottom of
https://consensus-health.torproject.org/#relayinfo and putting your
nickname or fingerprint there. As you say, the Ernest relay currently has
seven votes for Guard, so it gets the Guard flag, but the Alberta relay
only has 4 votes for Guard, and it needs a majority (5 out of 8) so it
doesn't get it. It's clearly right on the edge. I think the difference is
in measured bandwidth: moria1 and longclaw think it is above the median
bandwidth they see, while gabelmoo and maatuska and bastet think it is
below their median. I would not be surprised if it wavers back and forth,
getting and losing the Guard flag, for the next while.

(This medium-complexity answer is a bit more complex because the
consensus-health website can't reliably fetch each vote from each
directory authority each hour. For example, it's missing tor26's vote
this round. But those votes can still be found in the metrics data set,
e.g. https://collector.torproject.org/recent/relay-descriptors/ )

And the high-complexity answer is that you can see the individual
cut-offs published by each directory authority about your relay, in
their individual vote documents (some assembly required).

$ grep -A10 "^r Alberta" v3-status-votes|egrep "^(stats|w)"
w Bandwidth=4092 Measured=2700
stats wfu=0.997242 tk=845547 mtbf=128371243
w Bandwidth=4092
stats wfu=0.996686 tk=1534488 mtbf=709353
w Bandwidth=4092 Measured=2200
stats wfu=0.999081 tk=2596023 mtbf=2391699
w Bandwidth=4092 Measured=2000
stats wfu=0.999053 tk=2493149 mtbf=2234701
w Bandwidth=4092 Measured=1900
stats wfu=0.999090 tk=2558326 mtbf=2324742
w Bandwidth=4092 Measured=2000
stats wfu=0.999031 tk=2455223 mtbf=2224108
w Bandwidth=4092
stats wfu=0.998203 tk=1692074 mtbf=1269334
w Bandwidth=4092
stats wfu=0.987932 tk=2331276 mtbf=241054

and you can read about what these stats mean at
https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt#n2629

Hope this helps,
--Roger

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