Comment 0 for bug 1774249

Original reported in RH Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1584315

Tested on OSP12 (Pike), but appears to be still present on master. Should only occur if nova compute is configured to use local file instance storage.

Create instance A on compute X

Resize instance A to compute Y
  Domain is powered off
  /var/lib/nova/instances/<uuid A> renamed to <uuid A>_resize on X
  Domain is *not* undefined

On compute X:
  update_available_resource runs as a periodic task
  First action is to update self
  rt calls driver.get_available_resource()
  ...calls _get_disk_over_committed_size_total
  ...iterates over all defined domains, including the ones whose disks we renamed
  ...fails because a referenced disk no longer exists

Results in errors in nova-compute.log:

    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager [req-bd52371f-c6ec-4a83-9584-c00c5377acd8 - - - - -] Error updating resources for node compute-0.localdomain.: DiskNotFound: No disk at /var/lib/nova/instances/f3ed9015-3984-43f4-b4a5-c2898052b47d/disk
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager Traceback (most recent call last):
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager File "/usr/lib/python2.7/site-packages/nova/compute/manager.py", line 6695, in update_available_resource_for_node
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager rt.update_available_resource(context, nodename)
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager File "/usr/lib/python2.7/site-packages/nova/compute/resource_tracker.py", line 641, in update_available_resource
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager resources = self.driver.get_available_resource(nodename)
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 5892, in get_available_resource
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager disk_over_committed = self._get_disk_over_committed_size_total()
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 7393, in _get_disk_over_committed_size_total
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager config, block_device_info)
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 7301, in _get_instance_disk_info_from_config
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager dk_size = disk_api.get_allocated_disk_size(path)
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager File "/usr/lib/python2.7/site-packages/nova/virt/disk/api.py", line 156, in get_allocated_disk_size
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager return images.qemu_img_info(path).disk_size
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager File "/usr/lib/python2.7/site-packages/nova/virt/images.py", line 57, in qemu_img_info
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager raise exception.DiskNotFound(location=path)
    2018-05-30 02:17:08.647 1 ERROR nova.compute.manager DiskNotFound: No disk at /var/lib/nova/instances/f3ed9015-3984-43f4-b4a5-c2898052b47d/disk

And resource tracker is no longer updated. We can find lots of these in the gate.

Note that change Icec2769bf42455853cbe686fb30fda73df791b25 nearly mitigates this, but doesn't because task_state is not set while the instance is awaiting confirm.