[tor-bugs] #18580 [Core Tor/Tor]: exit relay fails with 'unbound' DNS resolver when lots of requests time-out

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#18580: exit relay fails with 'unbound' DNS resolver when lots of requests time-out
-------------------------------------------------+-------------------------
 Reporter:  Dhalgren                             |          Owner:  (none)
     Type:  defect                               |         Status:  new
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  unspecified
Component:  Core Tor/Tor                         |        Version:  Tor:
                                                 |  0.2.7.6
 Severity:  Major                                |     Resolution:
 Keywords:  tor-relay exit dns unbound needs-    |  Actual Points:
  diagnosis                                      |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------

Comment (by arma):

 Sebastian points out that we are now experiencing this bug on many large
 Tor exit relays, in #21394.

 So, ten points to Dhalgren for identifying and debugging it early. :)

 Also, am I reading the above correctly, that evdns does not scale well? If
 so, that is a thing that we should be able to fix on the Tor and/or
 libevent side.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/18580#comment:25>
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