[Bug 1688508] Re: libvirt-guests.sh fails to shutdown guests in parallel

[Dan Streetman]

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Title:
  libvirt-guests.sh fails to shutdown guests in parallel

Status in libvirt:
  Fix Released
Status in libvirt package in Ubuntu:
  Fix Released
Status in libvirt source package in Xenial:
  In Progress
Status in libvirt source package in Zesty:
  Won't Fix
Status in libvirt source package in Artful:
  In Progress

Bug description:
  [Environment]

  No LSB modules are available.
  Distributor ID:	Ubuntu
  Description:	Ubuntu 16.04.3 LTS
  Release:	16.04
  Codename:	xenial

  [Impact]

  There is a bug/race condition on libvirt-guests.service, that prevents
  the shutdown of guests to happen in parallel.

  The critical chain for this service is:

  libvirt-guests.service +20ms
  └─libvirt-bin.service @2.784s +140ms
    └─remote-fs.target @2.777s
      └─remote-fs-pre.target @2.775s
        └─open-iscsi.service @2.554s +116ms
          └─iscsid.service @2.525s +18ms
            └─network-online.target @2.502s
              └─network.target @1.955s
                └─networking.service @1.625s +299ms
                  └─network-pre.target @1.601s
                    └─cloud-init-local.service @405ms +1.072s
                      └─systemd-remount-fs.service @232ms +64ms
                        └─systemd-journald.socket @178ms
                          └─-.slice @117ms

  As an example, I have the following kvm host with 42 virtual
  machines.

  ubuntu at xenial-base:~$ virsh list --all
   Id    Name                           State
  ----------------------------------------------------
   12    locked-trusty-2                running
   13    locked-trusty-3                running
  [...]
   41    locked-trusty-42               running

  After rebooting the machine:

  [  250.999516] libvirt-guests.sh[4215]: Running guests on default URI: locked-trusty-2, locked-trusty-4, locked-trusty-12, locked-trusty-3, locked-trusty-5, locked-trusty-11, locked-trusty-10, locked-trusty-8, locked-trusty-9, locked-trusty-7, locked-trusty-6, locked-trusty-13, locked-trusty-14, locked-trusty-15, locked-trusty-16, locked-trusty-17, locked-trusty-18, locked-trusty-19, locked-trusty-20, locked-trusty-21, locked-trusty-22, locked-trusty-23, locked-trusty-24, locked-trusty-25, locked-trusty-26, locked-trusty-27, locked-trusty-28, locked-trusty-29, locked-trusty-30, locked-trusty-31, locked-trusty-32, locked-trusty-33, locked-trusty-34, locked-trusty-35, locked-trusty-36, locked-trusty-37, locked-trusty-38, locked-trusty-39, locked-trusty-40, locked-trusty-41, locked-trusty-42
  [  251.011367] libvirt-guests.sh[4215]: Shutting down guests on default URI...
  [  251.027072] libvirt-guests.sh[4215]: Starting shutdown on guest: locked-trusty-2
  [...]
  [  391.949941] libvirt-guests.sh[4215]: Waiting for 28 guests to shut down, 10 seconds left
  [  398.074405] libvirt-guests.sh[4215]: Waiting for 28 guests to shut down, 5 seconds left
  [  403.020479] libvirt-guests.sh[4215]: Timeout expired while shutting down domains
  [  OK  ] Stopped Suspend Active Libvirt Guests.
  [  OK  ] Stopped target System Time Synchronized.

  [Test Case]

   * Make sure the following variables are set in /etc/default/libvirt-
  guests (which are all default options):

  ON_SHUTDOWN=shutdown
  PARALLEL_SHUTDOWN=10
  SHUTDOWN_TIMEOUT=120

   * Create over 20 virtual machines (in my case, using uvt-kvm).

  $  for f in $(seq 0 40); do uvt-kvm create --memory 2000 --cpu 1
  locked-trusty-$f release=xenial arch=amd64 ; done

   * Reboot the machine and monitor the systemd service stop sequence
  or console output.

  (With systemd: systemctl start debug-shell and jumpt to ctrl+alt+f9)

  * Error message "Timeout expired while shutting down domains" should
  be displayed.

  [Regression Potential]

  * None identified.

  [Other Info]

  * There is a proposed patch in upstream already that has been already
  linked to this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1450141

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