warning message question

[Roger Dingledine]

On Sun, Jul 26, 2009 at 02:32:45AM -0500, Scott Bennett wrote:
>      Saturday morning, I got the following message.
> 
> Jul 25 09:33:57.004 [warn] Received http status code 502 ("Proxy Error") from server '80.190.246.100:80' while fetching consensus directory.
> 
> Can anyone explain the situation(s) that can result in such a message?

80.190.246.100:80 is the DirPort on gabelmoo, one of the v3 authorities.
So your relay was trying to get an updated version of the v3 consensus
from gabelmoo.

It looks like the way gabelmoo is listening on port 80 is by proxypassing
it through apache. You can read more about that approach in this poorly
organized faq entry:
https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#ServerForFirewalledClients

and at that particular moment, for some reason apache decided that
sending back a 502 proxy error was better than passing your request on.

For example, I bet this could happen if the gabelmoo relay was down at
the time.

--Roger