[tor-bugs] #27066 [Core Tor/Tor]: circuit_build_times_update_alpha(): Bug: Could not determine largest build time

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#27066: circuit_build_times_update_alpha(): Bug: Could not determine largest build
time
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 Reporter:  cstest                     |          Owner:  (none)
     Type:  defect                     |         Status:  new
 Priority:  Medium                     |      Milestone:  Tor:
                                       |  0.3.5.x-final
Component:  Core Tor/Tor               |        Version:  Tor: 0.3.3.9
 Severity:  Normal                     |     Resolution:
 Keywords:  034-backport 033-backport  |  Actual Points:
Parent ID:                             |         Points:
 Reviewer:                             |        Sponsor:
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Comment (by mikeperry):

 Ok I have a new theory, writing it here for the record:

 1. Circuit build times are being recorded while the default high timeout
 value (and high close timeout) is used. Lots of circuits take a while to
 complete, but successfully do so.
 2. Eventually, a low timeout value is learned.
 3. A SIGHUP arrives, which causes CBT to reload from the state file. While
 doing this, old compatibility code activates, and converts many/most of
 your previous timeout values to "abandoned" values.
 4. Finally, enough circuits time out again such that everything in the
 array is "abandonded".

 This set of events would be consistent with your loglines, especially if
 you have no lines from #27049.

 This still does not explain why this is v3 only, though.

 Is the SIGHUP that you are sending only being done when v3 is enabled? Can
 you not SIGHUP Tor and see if the issue persists, or is there some reason
 you need to HUP it?

 If for some reason you must SIGHUP Tor, I have a branch that disables this
 compatibility code upon SIGHUP, as well as resets CBT when these warns
 happen. The CBT reset *should* allow things to continue to work in that
 case (unless the connectivity/hang bug is not related to CBT at all):

 https://github.com/mikeperry-tor/tor/tree/bug27066-cbtreset
 https://github.com/mikeperry-tor/tor/archive/bug27066-cbtreset.zip

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27066#comment:10>
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