[tor-bugs] #28424 [Core Tor/Tor]: Refactor hs_service_callback() to no longer need to run once per second?

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#28424: Refactor hs_service_callback() to no longer need to run once per second?
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 Reporter:  nickm         |          Owner:  (none)
     Type:  defect        |         Status:  new
 Priority:  Medium        |      Milestone:  Tor: 0.4.0.x-final
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:                |  Actual Points:
Parent ID:  #28335        |         Points:
 Reviewer:                |        Sponsor:  Sponsor8-can
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Comment (by dgoulet):

 I've thought a bit about this. So the big problem is the hashring which
 require a fresh consensus in order to compute for each nodes the HSDir
 index using the SRV value. It doesn't change often (every 24h) but it is
 also about relay churn impact on the hashring thus it is done as much as
 we can.

 The problem doesn't lie in computing those but rather if we are in a
 "dormant" state, we don't have a fresh consensus and thus change in SRV
 or/and churn will affect reachability up to the point of _not_ being
 reachable (because SRV changed).

 We can refactor everything to instead being called every seconds would
 register a mainloop event in the time frame it needs to be woken up (for
 instance rotation time of descriptor).

 But without a fresh consensus (not participating in the network), we'll
 run into reachability issues pretty fast.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28424#comment:2>
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