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[Matt Riedemann <mriedem.os@xxxxxxxxx>]

** No longer affects: nova/newton

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https://bugs.launchpad.net/bugs/1737214

Title:
  Enabling guestfs.debug can hang guestfs.launch

Status in OpenStack Compute (nova):
  Fix Released
Status in OpenStack Compute (nova) ocata series:
  Confirmed
Status in OpenStack Compute (nova) pike series:
  In Progress

Bug description:
  I noticed this while debugging this change:

  https://review.openstack.org/#/c/524710/

  When we enable guestfs.debug, we're receiving events from guestfs and
  logging them.

  However, guestfs.launch is run in an eventlet thread pool, and running
  things within an eventlet thread pool for native apps is a no-no for
  doing logging because it can cause a greenthread switch that makes us
  lose the return from the guestfs.launch call, which eventually means
  we hang when trying to create the instance.

  So we need to just run guestfs.launch non-threaded if guestfs.debug is
  enabled.

  From the logs, you can see the guestfs.launch thread switch here:

  http://logs.openstack.org/50/524750/1/check/legacy-tempest-dsvm-
  neutron-full-
  centos-7/a7f051e/logs/screen-n-cpu.txt.gz#_Dec_04_13_43_19_941869

  And the logging callback here:

  http://logs.openstack.org/50/524750/1/check/legacy-tempest-dsvm-
  neutron-full-
  centos-7/a7f051e/logs/screen-n-cpu.txt.gz#_Dec_04_15_25_29_320753

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