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[Launchpad Bug Tracker <1764668@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package libvirt - 3.6.0-1ubuntu6.6

---------------
libvirt (3.6.0-1ubuntu6.6) artful; urgency=medium

  * Fix clean shut down of guests on system shutdown (LP: #1764668)
    - d/p/ubuntu/lp-1764668-do-not-report-unknown-guests.patch
    - d/p/ubuntu/lp-1764668-fix-check_guests_shutdown-loop.patch

 -- Christian Ehrhardt <christian.ehrhardt@xxxxxxxxxxxxx>  Wed, 25 Apr
2018 09:24:08 +0200

** Changed in: libvirt (Ubuntu Artful)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1764668

Title:
  guest cleanup script fails to iterate

Status in libvirt package in Ubuntu:
  Fix Released
Status in libvirt source package in Xenial:
  Fix Released
Status in libvirt source package in Artful:
  Fix Released
Status in libvirt source package in Bionic:
  Fix Released

Bug description:
  [Impact]

   * Due to a bug in a recent fix guests now are immediately considered shut
     down. Due to that the helper to shut down guests cleanly might not wait
     long enough.

   * backporting the upstream fix to the affected releases.

  [Test Case]

   * Spawn a few KVM guests through libvirt, e.g.
     $ uvt-simplestreams-libvirt --verbose sync --source http://cloud-images.ubuntu.com/daily arch=amd64 release=bionic label=daily
     $ uvt-kvm create --memory 128  --password ubuntu b1 arch=amd64 release=bionic label=daily
     $ uvt-kvm create --memory 128  --password ubuntu b2 arch=amd64 release=bionic label=daily
     $ uvt-kvm create --memory 128  --password ubuntu b3 arch=amd64 release=bionic label=daily

   * A) Shut down the computer and watch how it handles guest shutdown.

   * B) You can better track that if instead of a shutdown you call what the
     shutdown would via:
     $ sudo /usr/lib/libvirt/libvirt-guests.sh stop

   * It will consider guests as shut down no matter what, so you might want
     to modify guests to not shut down or if you have a system to do so use
     huge guests with plenty of dirty memory which will slow it down.
     One good trick is to start the guests right before stopping.
     Guests are not yet responding to shutdown signals at that time, so the 
     issue is revealed (not waiting on shutdown)
     To do so you could stop the guests and then do:
     $ virsh start b1; virsh start b2; virsh start b3;
     $ /usr/lib/libvirt/libvirt-guests.sh stop

     The bad case looks like:
     Running guests on default URI: b1, b2, b3
     Shutting down guests on default URI...
     Starting shutdown on guest: b1
     Starting shutdown on guest: b2
     Starting shutdown on guest: b3
     Waiting for 3 guests to shut down, 120 seconds left
     Shutdown of guest b1 complete.
     Shutdown of guest b2 complete.
     Shutdown of guest b3 complete.

     But you can check with virsh list they are still alive.
     The improved case at least properly waits like:
     ...
     Waiting for 3 guests to shut down, 120 seconds left
     Waiting for 3 guests to shut down, 115 seconds left
     Waiting for 3 guests to shut down, 110 seconds left
     ...
     
  [Regression Potential]

   * The fix "only" affects this shutdown handling and no other part of
     libvirt which limits the ranges of potential regressions.

   * The current issue is that we don't wait enough for the geusts, we can't
     wait "less" so we won't regress to be less forgiving slow-shutdowns,
     but if a mistake would be in the code the regression risk would
     be to slow down shutdowns - tests did not see that, but this section is
     about regression POTENTIAL so I thought I add it.

  [Other Info]

   * n/a

  ---

  The recent fix to libvirt-guests.sh.in works for what it intended to fix
  (variable scope) but failed to adapt the loop in check_guests_shutdown correctly.
  Due to that it currently detects all guests as "Failed to determine state of guest".

  It all works, but guests are just assumed dead and logs are spilled
  with false-positive warnings.

  A suggested fix is at:
  https://git.launchpad.net/~paelzer/libvirt/commit/?id=2ccca91678cd1091163490fd0b466b58c8be2b79

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