[tor-relays] 100K circuit request per minute for hours killed my relay

[Vort]

>> Jul 27 18:08:31.000 [notice] Circuit handshake stats since last time: 5198/5200 TAP, 3994625/3995090 NTor.

> TAP is used for hidden services to connect to intro and rendezvous
> points, and you're not seeing many extra TAP connections.

> So *if* this is related to hidden services, it is not connecting to the
> hidden service directly. Instead, it is sending (exit?) traffic through
> the relays in the hidden service circuit.

I have found that there are two patterns, which are associated with
  "assign_to_cpuworker failed" errors.
First one: heavy overload, millions of NTor handshakes, weight is
  decreased several times, relay can lose Guard state.
Second one: moderate overload, TAP handshakes slightly increased,
  weight is not affected.

Normal stats:
Jul 24 18:08:29.000 [notice] Circuit handshake stats since last time: 4892/4892 TAP, 61208/61208 NTor.
Jul 25 00:08:29.000 [notice] Circuit handshake stats since last time: 3753/3753 TAP, 61775/61775 NTor.
Jul 25 06:08:29.000 [notice] Circuit handshake stats since last time: 3218/3218 TAP, 57756/57756 NTor.
Jul 25 12:08:29.000 [notice] Circuit handshake stats since last time: 3538/3538 TAP, 56631/56631 NTor.
Jul 25 18:08:29.000 [notice] Circuit handshake stats since last time: 4188/4188 TAP, 60672/60672 NTor.

Overload #1 stats:
Jul 27 12:08:31.000 [notice] Circuit handshake stats since last time: 4715/4715 TAP, 100785/100785 NTor.
Jul 27 18:08:31.000 [notice] Circuit handshake stats since last time: 5198/5200 TAP, 3994625/3995090 NTor.
Jul 28 00:08:31.000 [notice] Circuit handshake stats since last time: 2771/2773 TAP, 4172331/4174404 NTor.
Jul 28 06:08:31.000 [notice] Circuit handshake stats since last time: 1304/1305 TAP, 3899551/3899941 NTor.
Jul 28 12:08:32.000 [notice] Circuit handshake stats since last time: 1415/1416 TAP, 3802487/3803824 NTor.
Jul 28 18:08:32.000 [notice] Circuit handshake stats since last time: 1895/1895 TAP, 843496/843724 NTor.
Jul 29 00:08:32.000 [notice] Circuit handshake stats since last time: 1948/1948 TAP, 34055/34055 NTor.

Overload #2 stats:
Jul 30 06:08:33.000 [notice] Circuit handshake stats since last time: 9288/9288 TAP, 60425/60425 NTor.
Jul 30 12:08:33.000 [notice] Circuit handshake stats since last time: 31739/32038 TAP, 37301/37307 NTor.
Jul 30 18:08:33.000 [notice] Circuit handshake stats since last time: 40316/40993 TAP, 36967/36972 NTor.
Jul 31 00:08:34.000 [notice] Circuit handshake stats since last time: 36414/36830 TAP, 36726/36730 NTor.
Jul 31 06:08:31.000 [notice] Circuit handshake stats since last time: 21715/21801 TAP, 40564/40564 NTor.


I'm not sure what this differences mean, but, maybe, this stats can
  help to distinguish the sources of overload (or prove that they
  are the same).


-- Vort