openstack
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nova
Code Issues Proposed changes

Merge "Reserve DISK_GB resource for the image cache" into stable/stein

This commit is contained in:
Zuul 2020-07-08 15:30:30 +00:00 committed by Gerrit Code Review
parent a78be40224 86be251451
commit f49d19fb6c
7 changed files with 166 additions and 1 deletions
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20
nova/conf/workarounds.py
View File

@ -248,6 +248,26 @@ Related options:
* ``compute_driver`` (libvirt)
* ``[libvirt]/images_type`` (rbd)
* ``instances_path``
"""),
cfg.BoolOpt('reserve_disk_resource_for_image_cache',
default=False,
help="""
If it is set to True then the libvirt driver will reserve DISK_GB resource for
the images stored in the image cache. If the
:oslo.config:option:`DEFAULT.instances_path` is on different disk partition
than the image cache directory then the driver will not reserve resource for
the cache.
Such disk reservation is done by a periodic task in the resource tracker that
runs every :oslo.config:option:`update_resources_interval` seconds. So the
reservation is not updated immediately when an image is cached.
Related options:
* :oslo.config:option:`DEFAULT.instances_path`
* :oslo.config:option:`image_cache_subdirectory_name`
* :oslo.config:option:`update_resources_interval`
"""),
]

27
nova/tests/unit/virt/libvirt/test_driver.py
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@ -18863,6 +18863,33 @@ class TestUpdateProviderTree(test.NoDBTestCase):
self.assertIn('Unexpected VGPU resource allocation on provider %s'
% uuids.other_rp, six.text_type(ex))
@mock.patch('nova.virt.libvirt.imagecache.ImageCacheManager.'
'get_disk_usage', return_value=1000)
def test_image_cache_disk_reservation(self, mock_cache_manager):
self.flags(reserved_host_disk_mb=1024)
self.flags(group='workarounds',
reserve_disk_resource_for_image_cache=False)
self.driver.update_provider_tree(self.pt, self.cn_rp['name'])
disk_reservation = self.pt.data(
self.cn_rp['uuid']).inventory['DISK_GB']['reserved']
# Only the reserved_host_disk_mb is counted
self.assertEqual(1, disk_reservation)
# Turn the cache reservation on
self.flags(group='workarounds',
reserve_disk_resource_for_image_cache=True)
self.driver.update_provider_tree(self.pt, self.cn_rp['name'])
disk_reservation = self.pt.data(
self.cn_rp['uuid']).inventory['DISK_GB']['reserved']
# Now both the reserved_host_disk_mb and the cache size is counted
# Note that the mock returns bytes which is rounded up to the next GB
self.assertEqual(2, disk_reservation)
class TraitsComparisonMixin(object):

61
nova/tests/unit/virt/libvirt/test_imagecache.py
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@ -730,3 +730,64 @@ class ImageCacheManagerTestCase(test.NoDBTestCase):
remove_lock=False)
mock_synchronized.assert_called_once_with(lock_file, external=True,
lock_path=lock_path)
@mock.patch('os.stat')
def test_cache_dir_is_on_same_dev_as_instances_dir(self, mock_stat):
mock_stat.side_effect = [mock.Mock(st_dev=0), mock.Mock(st_dev=1)]
manager = imagecache.ImageCacheManager()
self.assertFalse(manager.cache_dir_is_on_same_dev_as_instances_dir)
mock_stat.assert_has_calls([
mock.call(CONF.instances_path),
mock.call(
os.path.join(
CONF.instances_path,
CONF.image_cache_subdirectory_name))])
mock_stat.reset_mock()
mock_stat.side_effect = [mock.Mock(st_dev=0), mock.Mock(st_dev=0)]
self.assertTrue(manager.cache_dir_is_on_same_dev_as_instances_dir)
@mock.patch('nova.virt.libvirt.imagecache.ImageCacheManager.'
'cache_dir_is_on_same_dev_as_instances_dir',
new=mock.PropertyMock(return_value=False))
def test_get_disk_usage_cache_is_on_different_disk(self):
manager = imagecache.ImageCacheManager()
self.assertEqual(0, manager.get_disk_usage())
@mock.patch('os.listdir')
@mock.patch('nova.virt.libvirt.imagecache.ImageCacheManager.'
'cache_dir_is_on_same_dev_as_instances_dir',
new=mock.PropertyMock(return_value=True))
def test_get_disk_usage_empty(self, mock_listdir):
mock_listdir.return_value = []
manager = imagecache.ImageCacheManager()
self.assertEqual(0, manager.get_disk_usage())
@mock.patch('os.path.isfile')
@mock.patch('os.listdir')
@mock.patch('os.stat')
@mock.patch('nova.virt.libvirt.imagecache.ImageCacheManager.'
'cache_dir_is_on_same_dev_as_instances_dir',
new=mock.PropertyMock(return_value=True))
def test_get_disk_usage(self, mock_stat, mock_listdir, mock_isfile):
mock_stat.side_effect = [
# stat calls on each file in the cache directory to get the size
mock.Mock(st_blocks=10), # foo
mock.Mock(st_blocks=20), # bar
]
mock_listdir.return_value = ['foo', 'bar', 'some-dir']
mock_isfile.side_effect = [
True, # foo
True, # bar
False, # some-dir
]
manager = imagecache.ImageCacheManager()
# size is calculated from as st_blocks * 512
self.assertEqual(10 * 512 + 20 * 512, manager.get_disk_usage())

9
nova/virt/imagecache.py
View File

@ -107,3 +107,12 @@ class ImageCacheManager(object):
populated in the cached stats will be used for the cache management.
"""
raise NotImplementedError()
def get_disk_usage(self):
"""Return the size of the physical disk space used for the cache.
:returns: The disk space in bytes that is occupied from
CONF.instances_path or zero if the cache directory is mounted
to a different disk device.
"""
raise NotImplementedError()

15
nova/virt/libvirt/driver.py
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@ -6789,7 +6789,8 @@ class LibvirtDriver(driver.ComputeDriver):
'max_unit': disk_gb,
'step_size': 1,
'allocation_ratio': ratios[orc.DISK_GB],
'reserved': self._get_reserved_host_disk_gb_from_config(),
'reserved': (self._get_reserved_host_disk_gb_from_config() +
self._get_disk_size_reserved_for_image_cache()),
}
# NOTE(sbauza): For the moment, the libvirt driver only supports
@ -8846,6 +8847,18 @@ class LibvirtDriver(driver.ComputeDriver):
except Exception:
pass
def _get_disk_size_reserved_for_image_cache(self):
"""Return the amount of DISK_GB resource need to be reserved for the
image cache.
:returns: The disk space in GB
"""
if not CONF.workarounds.reserve_disk_resource_for_image_cache:
return 0
return compute_utils.convert_mb_to_ceil_gb(
self.image_cache_manager.get_disk_usage() / 1024.0 / 1024.0)
def _is_storage_shared_with(self, dest, inst_base):
# NOTE (rmk): There are two methods of determining whether we are
# on the same filesystem: the source and dest IP are the

25
nova/virt/libvirt/imagecache.py
View File

@ -419,3 +419,28 @@ class ImageCacheManager(imagecache.ImageCacheManager):
# perform the aging and image verification
self._age_and_verify_cached_images(context, all_instances, base_dir)
self._age_and_verify_swap_images(context, base_dir)
def get_disk_usage(self):
if not self.cache_dir_is_on_same_dev_as_instances_dir:
return 0
# NOTE(gibi): we need to use the disk size occupied from the file
# system as images in the cache will not grow to their virtual size.
# NOTE(gibi): st.blocks is always measured in 512 byte blocks see man
# fstat
return sum(
os.stat(os.path.join(self.cache_dir, f)).st_blocks * 512
for f in os.listdir(self.cache_dir)
if os.path.isfile(os.path.join(self.cache_dir, f)))
@property
def cache_dir(self):
return os.path.join(
CONF.instances_path, CONF.image_cache_subdirectory_name)
@property
def cache_dir_is_on_same_dev_as_instances_dir(self):
# NOTE(gibi): this does not work on Windows properly as st_dev is
# always 0
return (os.stat(CONF.instances_path).st_dev ==
os.stat(self.cache_dir).st_dev)

10
releasenotes/notes/bug-1878024-reserve-disk-for-image-cache-ef6688f869b12bcb.yaml Normal file
View File

@ -0,0 +1,10 @@
---
fixes:
- |
A new ``[workarounds]/reserve_disk_resource_for_image_cache`` config
option was added to fix the `bug 1878024`_ where the images in the compute
image cache overallocate the local disk. If this new config is set then the
libvirt driver will reserve DISK_GB resources in placement based on the
actual disk usage of the image cache.
.. _bug 1878024: https://bugs.launchpad.net/nova/+bug/1878024