[tor-relays] Circuit creation "storms" overwhelming Raspberry Pi?

torsion at ftml.net torsion at ftml.net
Tue Mar 19 01:18:25 UTC 2013


I'm also seeing occasional messages like this on the Pi (it never lasts
long):

18:13:24 [ARM_NOTICE] Relay resumed
18:13:18 [ARM_NOTICE] Relay unresponsive (last heartbeat: Mon Mar 18
18:13:04 2013)
17:28:43 [ARM_NOTICE] Relay resumed
17:28:38 [ARM_NOTICE] Relay unresponsive (last heartbeat: Mon Mar 18
17:28:25 2013)
14:12:26 [ARM_NOTICE] Relay resumed
14:12:20 [ARM_WARN] Deduplication took too long. Its current
implementation has difficulty handling large logs so disabling it to
keep the interface responsive.
14:12:20 [ARM_NOTICE] Relay unresponsive (last heartbeat: Mon Mar 18
14:12:06 20

On Mon, Mar 18, 2013, at 01:00 PM, torsion at ftml.net wrote:
> Hi there, I just joined the mailing list and apologized if this has been
> discussed before.  I did find discussion of a similar issue in January
> 2013's archive:
> 
> https://lists.torproject.org/pipermail/tor-relays/2013-January/001809.html
> 
> It's important to note that I believe I've seen (but didn't save logs) a
> couple "circuit creation burst" events on my established relay (about
> 5Mbps, stable, guard, non-exit) which was mostly able to handle it
> without crashing as it has plenty of RAM and the above-mentioned
> messages - "Your computer is too slow to handle this many circuit
> creation requests! Please consider using the MaxAdvertisedBandwidth
> config option or choosing a m ore restricted exit policy." - appear only
> with the relay is under load for other reasons AND a large number of
> circuits are being suddenly created.
> 
> I wondered if this was some kind of DOS attempt but didn't think much of
> it because my fast relay continued working fine.
> 
> However, I've just set up a Raspberry Pi, the 512MB model, as a relay on
> a slower connection.  Here are the relevant settings on this relay:
> 
> RelayBandwidthRate 130 KB
> RelayBandwidthBurst 340 KB
> 
> The Pi has a fairly slow CPU, so I'd occasionally get messages about log
> deduplication being too slow or something, but didn't think much of it. 
> I finally got the relay up and left it up for over 24 hours.  When I
> woke up this morning it had crashed.  Here are the relevant log messages
> - note the huge jump in number of circuits between 22:35 and 04:35
> (maybe I got the Stable flag), then the storm of circuit open requests
> starting at 05:49.  Eventually I believe the Pi ran out of memory and
> killed the tor process.
> 
> What's very interesting here is that my fast VPS relay with a
> RelayBandwidthRate over 5x faster is almost never handling much more
> than 1000 circuits, so why all of a sudden the demand on the Pi that's
> advertising a lower bandwidth rate?
> 
> Mar 17 22:35:00.000 [notice] Heartbeat: Tor's uptime is 1 day 0:00
> hours, with 26 circuits open. I've sent 974.13 MB and received 969.92
> MB.
> Mar 18 04:35:00.000 [notice] Heartbeat: Tor's uptime is 1 day 6:00
> hours, with 972 circuits open. I've sent 1.61 GB and received 1.59 GB.
> Mar 18 05:49:44.000 [warn] Your computer is too slow to handle this many
> circuit creation requests! Please consider using the
> MaxAdvertisedBandwidth config option or choosing a more restricted exit
> policy.
> Mar 18 05:49:44.000 [warn] Failed to hand off onionskin. Closing.
> Mar 18 05:50:44.000 [warn] Your computer is too slow to handle this many
> circuit creation requests! Please consider using the
> MaxAdvertisedBandwidth config option or choosing a more restricted exit
> policy. [5817 similar message(s) suppressed in last 60 seconds]
> Mar 18 05:52:30.000 [warn] Your system clock just jumped 101 seconds
> forward; assuming established circuits no longer work.
> Mar 18 05:53:51.000 [warn] Your computer is too slow to handle this many
> circuit creation requests! Please consider using the
> MaxAdvertisedBandwidth config option or choosing a more restricted exit
> policy. [1055 similar message(s) suppressed in last 60 seconds]
> Mar 18 05:55:14.000 [warn] Your computer is too slow to handle this many
> circuit creation requests! Please consider using the
> MaxAdvertisedBandwidth config option or choosing a more restricted exit
> policy. [329 similar message(s) suppressed in last 60 seconds]
> 
> I'd like to figure out just how much the Raspberry Pi is capable of,
> because it could be a cheap way to build out the relay network by people
> who want to donate bandwidth - but of course it needs to be stable, and
> something about my setup is not.
> 
> Also:
> 
> Mar 16 20:55:33.000 [notice] No AES engine found; using AES_* functions.
> 
> I have no idea if the Broadcom BCM2835 SoC (ARM1176JZF-S CPU) in the Pi
> has any AES capability, but it'd be great to find out.
> 
> _______________________________________________
> tor-relays mailing list
> tor-relays at lists.torproject.org
> https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-relays


More information about the tor-relays mailing list