[tor-relays] Bandwidth Authority PID Feedback Experiment #2 Starting

[Mike Perry]

Thus spake Mike Perry (mikeperry at torproject.org):

> Thus spake Tim Wilde (twilde at cymru.com):
> 
> > > I try to keep everything I do documented on that wiki. All these
> > > servers run four instances of Tor each (one per core) and traffic
> > > is accounted for in total. Also, keep in mind that vnstat counts
> > > both incoming and outgoing traffic, so 700Mbps in vnstat are really
> > > only 375 per direction.
> > 
> > Ah, okay, thanks for the clarification, I was thinking those numbers
> > were for single Tor instances.  That makes me feel a lot better then,
> > especially with the combination of directions. :)  I'm pushing around
> > 600Mb/sec total in+out on my piece of bit iron so I'm much closer to
> > the same ballpark than I thought.  Thanks, and thanks again for your
> > documentation!
> 
> Moritz, Andy, Tim, and others with Gbit+ Guards and/or Exits:
> 
> Could you guys ensure you are not running into TCP socket exhaustion
> on any of your relays? It is a possibility, esp for Guard+Exits with
> gobs of CPU and gobs of throughput.
> 
> I am curious if we will need to do this or not:
> https://trac.torproject.org/projects/tor/ticket/4709

It looks like Moritz is seeing some evidence of TCP sourceport
exhaustion in his Tor logs:
"[warn] Error binding network socket: Address already in use".

He's also monitoring TCP connection counts on each IP interface:
netstat -ntap | grep $INTERFACE_IP | wc -l

It appears that right now, he's at only about ~10k connections per IP,
and not experiencing any log lines at the moment. It is possible this
is a transient condition caused by overly-agressive scrapers and/or
torrenters who flock to the node for a short while and then move on?

Reports on the recent appearance or prevelance increase of that or
other warns from others will be helpful.


-- 
Mike Perry
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