openstack/nova
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Merge "Rebase qcow2 images when unshelving an instance"

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Zuul 2020-08-17 15:29:53 +00:00 committed by Gerrit Code Review
commit 2cc0511376
2 changed files with 106 additions and 0 deletions
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68
nova/tests/unit/virt/libvirt/test_driver.py
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@ -22622,6 +22622,74 @@ class LibvirtDriverTestCase(test.NoDBTestCase, TraitsComparisonMixin):
self.assertEqual('migrating instance across cells',
mock_debug.call_args[0][2])
@mock.patch.object(libvirt_driver.LibvirtDriver, '_try_fetch_image_cache')
@mock.patch.object(libvirt_driver.LibvirtDriver, '_rebase_with_qemu_img')
def _test_unshelve_qcow2_rebase_image_during_create(self,
mock_rebase, mock_fetch, original_image_in_glance=True):
self.flags(images_type='qcow2', group='libvirt')
# Original image ref from where instance was created, before SHELVE
# occurs, base_root_fname is related backing file name.
base_image_ref = 'base_image_ref'
base_root_fname = imagecache.get_cache_fname(base_image_ref)
# Snapshot image ref created during SHELVE.
shelved_image_ref = 'shelved_image_ref'
shelved_root_fname = imagecache.get_cache_fname(shelved_image_ref)
# Instance state during unshelve spawn().
inst_params = {
'image_ref': shelved_image_ref,
'vm_state': vm_states.SHELVED_OFFLOADED,
'system_metadata': {'image_base_image_ref': base_image_ref}
}
instance = self._create_instance(params=inst_params)
disk_images = {'image_id': instance.image_ref}
instance_dir = libvirt_utils.get_instance_path(instance)
disk_path = os.path.join(instance_dir, 'disk')
drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
if original_image_in_glance:
# We expect final backing file is original image, not shelved one.
expected_backing_file = os.path.join(
imagecache.ImageCacheManager().cache_dir,
base_root_fname)
else:
# None means rebase will merge backing file into disk(flatten).
expected_backing_file = None
mock_fetch.side_effect = [
None,
exception.ImageNotFound(image_id=base_image_ref)
]
drvr._create_and_inject_local_root(
self.context, instance, False, '', disk_images, None, None)
mock_fetch.assert_has_calls([
mock.call(test.MatchType(nova.virt.libvirt.imagebackend.Qcow2),
libvirt_utils.fetch_image,
self.context, shelved_root_fname, shelved_image_ref,
instance, instance.root_gb * units.Gi, None),
mock.call(test.MatchType(nova.virt.libvirt.imagebackend.Qcow2),
libvirt_utils.fetch_image,
self.context, base_root_fname, base_image_ref,
instance, None)])
mock_rebase.assert_called_once_with(disk_path, expected_backing_file)
def test_unshelve_qcow2_rebase_image_during_create(self):
# Original image is present in Glance. In that case the 2nd
# fetch succeeds and we rebase instance disk to original image backing
# file, instance is back to nominal state: after unshelve,
# instance.image_ref will match current backing file.
self._test_unshelve_qcow2_rebase_image_during_create()
def test_unshelve_qcow2_rebase_image_during_create_notfound(self):
# Original image is no longer available in Glance, so 2nd fetch
# will failed (HTTP 404). In that case qemu-img rebase will merge
# backing file into disk, removing backing file dependency.
self._test_unshelve_qcow2_rebase_image_during_create(
original_image_in_glance=False)
@mock.patch('nova.virt.libvirt.driver.imagebackend')
@mock.patch('nova.virt.libvirt.driver.LibvirtDriver._inject_data')
@mock.patch('nova.virt.libvirt.driver.imagecache')

38
nova/virt/libvirt/driver.py
View File

@ -4123,6 +4123,14 @@ class LibvirtDriver(driver.ComputeDriver):
root_fname, disk_images['image_id'],
instance, size, fallback_from_host)
# During unshelve on Qcow2 backend, we spawn() using snapshot image
# created during shelve. Extra work is needed in order to rebase
# disk image to its original image_ref. Disk backing file will
# then represent back image_ref instead of shelved image.
if (instance.vm_state == vm_states.SHELVED_OFFLOADED and
isinstance(backend, imagebackend.Qcow2)):
self._finalize_unshelve_qcow2_image(context, instance, backend)
if need_inject:
self._inject_data(backend, instance, injection_info)
@ -4132,6 +4140,36 @@ class LibvirtDriver(driver.ComputeDriver):
return created_disks
def _finalize_unshelve_qcow2_image(self, context, instance, backend):
# NOTE(aarents): During qcow2 instance unshelve, backing file
# represents shelved image, not original instance.image_ref.
# We rebase here instance disk to original image.
# This second fetch call does nothing except downloading original
# backing file if missing, as image disk have already been
# created/resized by first fetch call.
base_dir = self.image_cache_manager.cache_dir
base_image_ref = instance.system_metadata.get('image_base_image_ref')
root_fname = imagecache.get_cache_fname(base_image_ref)
base_backing_fname = os.path.join(base_dir, root_fname)
try:
self._try_fetch_image_cache(backend, libvirt_utils.fetch_image,
context, root_fname, base_image_ref,
instance, None)
except exception.ImageNotFound:
# We must flatten here in order to remove dependency with an orphan
# backing file (as shelved image will be dropped once unshelve
# is successfull).
LOG.warning('Current disk image is created on top of shelved '
'image and cannot be rebased to original image '
'because it is no longer available in the image '
'service, disk will be consequently flattened.',
instance=instance)
base_backing_fname = None
LOG.info('Rebasing disk image.', instance=instance)
self._rebase_with_qemu_img(backend.path, base_backing_fname)
def _create_configdrive(self, context, instance, injection_info,
rescue=False):
# As this method being called right after the definition of a