[tor-relays] "Failed to find node for hop #1 of our path"

[Roger Dingledine]

On Thu, Nov 09, 2023 at 06:33:08PM -0500, William Denton wrote:
> Lately my relay hasn't been seeing much traffic, which I didn't notice for a
> while, but now I'm turning my attention to it.  I just updated to 0.4.8.9
> and see these notices (with some lines cut out):

Thanks for running a relay!

Do you know if you were seeing those messages on earlier Tor versions too?

> Nov 09 13:36:42.000 [notice] Tor has not observed any network activity for the past 521 seconds. Disabling circuit build timeout recording.
> Nov 09 13:38:03.000 [notice] Failed to find node for hop #1 of our path. Discarding this circuit.

These are client-side messages, that is, your Tor is acting as both a
relay (because you configured it that way) and a client (in case you
try to use it that way), and it is not finding itself to be stable as
a client.

These particular circuits are probably the exploratory testing circuits
that Tor clients make at first, to understand how fast their network is
in order to avoid using the bottom 20% ("long tail") of circuits that
take the longest to make.

> There are hundreds of those notices about failing to find a node for hop #1.
> (I don't know why it complains about the network being down to 2013 seconds
> (over half an hour), because I didn't notice anything, but there were scores
> of the same warnings before that.)
> 
> What would cause this, or what could I do to identify the problem?

Well, the first question is, are you sure your network connection is
stable and working this whole time? An easy explanation would be that you
had connectivity problems during that time, and from a relay perspective
Tor just sat there patiently not minding that nobody was arriving, but
from a client perspective it noticed that something was wrong and said so.

I am guessing that this is your relay:
https://metrics.torproject.org/rs.html#details/2A6E7ABF43F9796AD4A13DF2B2047F90E7291A5F

Another possibility, which I don't think applies in your case, is that
your relay is so overwhelmed with traffic, and/or is rate limiting all of
its traffic, that the client-side testing circuits are squeezed out. But
based on the bandwidth graphs I don't think that's happening here.

--Roger