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[Matt Riedemann <mriedem.os@xxxxxxxxx>]

** Also affects: nova/ocata
   Importance: Undecided
       Status: New

** Changed in: nova/ocata
     Assignee: (unassigned) => Lee Yarwood (lyarwood)

** Changed in: nova/ocata
       Status: New => In Progress

** Changed in: nova/ocata
   Importance: Undecided => Low

** Tags added: libvirt migrate

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https://bugs.launchpad.net/bugs/1666831

Title:
  Nova recreates instance directory after migration/resize

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

Bug description:
  Description
  ===========
  Nova recreates instance directory on source host after successful migration/resize when using QEMU Qcow2 file drives.

  
  Nova after migration executes method driver.confirm_migration().
  This method cleans instance directory (instance directory with suffix _resize):

  nova/virt/libvirt/driver.py
  1115         if os.path.exists(target):
  1116             # Deletion can fail over NFS, so retry the deletion as required.
  1117             # Set maximum attempt as 5, most test can remove the directory
  1118             # for the second time.
  1119             utils.execute('rm', '-rf', target, delay_on_retry=True,
  1120                           attempts=5)

  After that Nova executes:
  1122             root_disk = self.image_backend.by_name(instance, 'disk')

  root_disk is used to remove rdb snapshots, but during execution of
  self.image_backend.by_name() nova recreates instance directory.

  Flow:

  driver.confirm_migration()->self._cleanup_resize()->self.image_backend.by_name()
  -> (nova/virt/libvirt/imagebackend.py)
  image_backend.by_name()->Qcow2.__init__()->Qcow2.resolve_driver_format().

  Qcow2.resolve_driver_format():
   344             if self.disk_info_path is not None:
   345                 fileutils.ensure_tree(os.path.dirname(self.disk_info_path))
   346                 write_to_disk_info_file()

  
  Steps to reproduce
  ==================

  - spawn instance
  - migrate/resize instance
  - check that instance dir on old host still exists (example: /home/instances/<instance_uuid>/disk.info

  
  Expected result
  ===============
  After migration directory /home/instances/<instance_uuid> and file /home/instances/<instance_uuid> should not exist.

  Actual result
  =============
  Nova leaves instance directory after migration/resize.

  
  Environment
  ===========
  1. Openstack Newton (it seems master is affected too).

  2. Libvirt + KVM

  3. Qcow2 file images on local disk.

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