[tor-bugs] #22421 [Core Tor/Tor]: Update fallback config comment for exponential backoff

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#22421: Update fallback config comment for exponential backoff
------------------------------+--------------------------------
     Reporter:  teor          |      Owner:
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: 0.3.1.x-final
    Component:  Core Tor/Tor  |    Version:  Tor: 0.2.9.1-alpha
     Severity:  Normal        |   Keywords:  fallback, comment
Actual Points:  0.1           |  Parent ID:
       Points:  0.1           |   Reviewer:
      Sponsor:                |
------------------------------+--------------------------------
 We modified the fallback behaviour when we merged the exponential backoff
 code in 0.2.9.1-alpha, and again in #17750:
 {{{
 /* 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) */
   V(ClientBootstrapConsensusAuthorityDownloadSchedule, CSV_INTERVAL,
     "6, 11, 3600, 10800, 25200, 54000, 111600, 262800" /* 3 days + 1 hour
 */),
   V(ClientBootstrapConsensusFallbackDownloadSchedule, CSV_INTERVAL,
     "0, 1, 4, 11, 3600, 10800, 25200, 54000, 111600, 262800"),
   /* When clients only have authorities available, they use this schedule:
 */
   V(ClientBootstrapConsensusAuthorityOnlyDownloadSchedule, CSV_INTERVAL,
     "0, 3, 7, 3600, 10800, 25200, 54000, 111600, 262800"),
 }}}

 The behaviour is now:
 {{{
 /* With the ClientBootstrapConsensus*Download* below:
    * Clients with only authorities will try:
    *  - at least 3 authorities over 10 seconds, then exponentially
 backoff, with the next attempt 3-21 seconds later,
    * Clients with authorities and fallbacks will try:
    *  - at least 2 authorities and 4 fallbacks over 21 seconds, then
 exponentially backoff, with the next attempts 4-33 seconds later,
    * 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.
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22421>
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