[tor-bugs] #20534 [Core Tor/Tor]: Revise hard-coded download schedules

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#20534: Revise hard-coded download schedules
-------------------------------------------+-------------------------------
 Reporter:  teor                           |          Owner:
     Type:  defect                         |         Status:  merge_ready
 Priority:  Medium                         |      Milestone:  Tor:
                                           |  0.2.9.x-final
Component:  Core Tor/Tor                   |        Version:  Tor:
                                           |  0.2.9.1-alpha
 Severity:  Normal                         |     Resolution:
 Keywords:  regression, CoreTorTeam201611  |  Actual Points:
Parent ID:  #20499                         |         Points:  0.5
 Reviewer:                                 |        Sponsor:
-------------------------------------------+-------------------------------

Comment (by teor):

 Here's a relevant comment from the 0.2.8 #4483 implementation in config.c.
 We can contrast it with the 0.2.9 #15942 implementation:

 {{{
  /* With the ClientBootstrapConsensus*Download* below:
    * Clients with only authorities will try:
    *  - 3 authorities over 10 seconds, then wait 60 minutes.
    * Clients with authorities and fallbacks will try:
    *  - 2 authorities and 4 fallbacks over 21 seconds, then wait 60
 minutes.
    * Clients will also retry when an application request arrives.
    * After a number of failed reqests, clients retry every 3 days + 1
 hour.
    *
    * Clients used to try 2 authorities over 10 seconds, then wait for
    * 60 minutes or an application request.
    *
    * When clients have authorities and fallbacks available, they use these
    * schedules: (we stagger the times to avoid thundering herds) */
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20534#comment:14>
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