[tor-bugs] #24228 [Core Tor/Tor]: Tor keeps on creating new circuits even when it's idle

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#24228: Tor keeps on creating new circuits even when it's idle
------------------------------+--------------------------------
     Reporter:  asn           |      Owner:  (none)
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: 0.3.3.x-final
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 Something is weird on latest master, and Tor will keep on creating new
 circuits even when it's completely idle. We are talking about 10 circuits
 per minute. I added a hook in `circuit_predict_and_launch_new()` and here
 is what I see:
 {{{
 Nov 10 15:56:26.000 [info] circuit_predict_and_launch_new(): Have 0 clean
 circs (0 internal), need another exit circ.
 Nov 10 15:56:27.000 [info] circuit_predict_and_launch_new(): Have 1 clean
 circs (0 internal), need another exit circ.
 Nov 10 15:56:28.000 [info] circuit_predict_and_launch_new(): Have 2 clean
 circs (0 uptime-internal, 0 internal), need another hidden service circ.
 Nov 10 15:56:29.000 [info] circuit_predict_and_launch_new(): Have 3 clean
 circs (1 uptime-internal, 1 internal), need another hidden service circ.
 Nov 10 15:56:30.000 [info] circuit_predict_and_launch_new(): Have 4 clean
 circs (2 uptime-internal, 2 internal), need another hidden service circ.
 Nov 10 15:56:31.000 [info] circuit_predict_and_launch_new(): Have 4 clean
 circs (2 uptime-internal, 2 internal), need another hidden service circ.
 Nov 10 15:56:42.000 [info] circuit_predict_and_launch_new(): Have 5 clean
 circs need another buildtime test circ.
 Nov 10 15:56:53.000 [info] circuit_predict_and_launch_new(): Have 6 clean
 circs need another buildtime test circ.
 Nov 10 15:57:04.000 [info] circuit_predict_and_launch_new(): Have 7 clean
 circs need another buildtime test circ.
 Nov 10 15:57:15.000 [info] circuit_predict_and_launch_new(): Have 8 clean
 circs need another buildtime test circ.
 Nov 10 15:57:26.000 [info] circuit_predict_and_launch_new(): Have 9 clean
 circs need another buildtime test circ.
 Nov 10 15:57:37.000 [info] circuit_predict_and_launch_new(): Have 10 clean
 circs need another buildtime test circ.
 Nov 10 15:57:48.000 [info] circuit_predict_and_launch_new(): Have 11 clean
 circs need another buildtime test circ.
 Nov 10 15:57:50.000 [info] circuit_predict_and_launch_new(): Have 6 clean
 circs (0 uptime-internal, 0 internal), need another hidden service circ.
 Nov 10 15:57:51.000 [info] circuit_predict_and_launch_new(): Have 7 clean
 circs (1 uptime-internal, 1 internal), need another hidden service circ.
 Nov 10 15:57:52.000 [info] circuit_predict_and_launch_new(): Have 8 clean
 circs (2 uptime-internal, 2 internal), need another hidden service circ.
 Nov 10 15:58:03.000 [info] circuit_predict_and_launch_new(): Have 9 clean
 circs need another buildtime test circ.
 Nov 10 15:58:14.000 [info] circuit_predict_and_launch_new(): Have 10 clean
 circs need another buildtime test circ.
 Nov 10 15:58:25.000 [info] circuit_predict_and_launch_new(): Have 8 clean
 circs need another buildtime test circ.
 Nov 10 15:58:36.000 [info] circuit_predict_and_launch_new(): Have 9 clean
 circs need another buildtime test circ.
 Nov 10 15:58:47.000 [info] circuit_predict_and_launch_new(): Have 10 clean
 circs need another buildtime test circ.
 Nov 10 15:58:52.000 [info] circuit_predict_and_launch_new(): Have 6 clean
 circs (1 uptime-internal, 1 internal), need another hidden service circ.
 Nov 10 15:58:53.000 [info] circuit_predict_and_launch_new(): Have 6 clean
 circs (1 uptime-internal, 1 internal), need another hidden service circ.
 Nov 10 15:58:54.000 [info] circuit_predict_and_launch_new(): Have 7 clean
 circs (2 uptime-internal, 2 internal), need another hidden service circ.
 }}}

 Seems like Tor continuously thinks it needs HS circs and build time
 testing circs. This probably causes lots of unneeded traffic on the
 network.

 Not sure how far back in Tor releases this goes.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24228>
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