[tor-bugs] #26930 [Core Tor/Tor]: Potential thundering herd HS upload once a day with hsv3

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#26930: Potential thundering herd HS upload once a day with hsv3
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     Reporter:  asn      |      Owner:  (none)
         Type:  defect   |     Status:  new
     Priority:  High     |  Milestone:  Tor: 0.3.5.x-final
    Component:  Core     |    Version:
  Tor/Tor                |   Keywords:  tor-hs hsv3 thundering-herd
     Severity:  Normal   |  performance network-health
Actual Points:           |  Parent ID:
       Points:           |   Reviewer:
      Sponsor:           |
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 Here is a potential bug we found with dgoulet at HOPE.

 In `set_rotation_time()` we set the rotation time of the next descriptor
 to the next midnight UTC with no randomization at all:
 {{{
   service->state.next_rotation_time =
     sr_state_get_start_time_of_current_protocol_run() +
     sr_state_get_protocol_run_duration();
 }}}

 After descriptors get rotated, a new descriptor is built and uploaded, so
 it might be the case that all hsv3s upload that new descriptor at the same
 time at midnight UTC.

 We should investigate more.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26930>
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