[tor-bugs] #22883 [Core Tor/Tor]: Bridge unavailable during differential consensus update

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#22883: Bridge unavailable during differential consensus update
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     Reporter:  torvlnt33r    |      Owner:
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:
    Component:  Core Tor/Tor  |    Version:  Tor: 0.3.1.4-alpha
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 After updating Tor from 0.3.0.9 to 0.3.1.4 (on a Raspberry Pi running
 Raspbian), I observed that my bridge became unable to answer new
 connection requests for extended periods, from 10 to 20 minutes or more,
 while tor process uses all available cpu (more than 90% on average - with
 no corresponding traffic for clients) and files are updated in
 /var/lib/tor/diff-cache directory.
 (For example, if I launch a TorBrowser using this bridge during such an
 update, it remains blocked before opening the Welcome window, and the
 corresponding client tor process remains blocked after "Bootstrapped 90%:
 Establishing a Tor circuit", for 10 minutes or more).
 So I had to downgrade to 0.3.0.9, so that my bridge doesn't become
 unavailable for a total of several hours per day.

 May I suggest that an option make it possible to choose between the new
 differential update mode and the traditional one?
 First, this would be necessary for some (like me) to keep following new
 Tor versions long term.
 And even on more powerful platforms, and even if a better handling of
 priorities could make it possible for main Tor thread to remain available
 on Pi, Tor relay operators might want to make different choices between
 minimizing bandwidth for consensus transfer or minimizing cpu usage, and
 hence power consumption. (Please think of the Planet globally, and not
 only of the network ;) )

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22883>
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