openstack
/
nova
Code Issues Proposed changes

rbd_utils: wrap blocking calls in tpool.Proxy() 

librbd is a Python binding around a C library, which is not aware of
eventlet - all the calls to the functions from this library will block
the whole nova-compute process for duration of a call. To make sure
nova-compute remains responsive we need to wrap all the calls in
tpool.Proxy() eventlet helper, that switches the execution context
back to the event loop, while the call is executed in a native OS
thread from a pool.

Prefer tpool.Proxy() to tpool.execute() here as the former allows for
wrapping objects and automatically executes all the method calls in
native OS threads, while the latter needs to be applied to each
method call in the code repeatedly.

Existing calls are modified for the sake of consistency.

Closes-Bug: #1607461

Change-Id: I743ab372332eb656258a476ae91f5e8fd2cbdc99
This commit is contained in:
Roman Podoliaka 2016-07-28 20:08:44 +03:00
parent 9add76ee59
commit 3405a28688
2 changed files with 45 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
nova/tests/unit/virt/libvirt/storage/test_rbd.py
View File

@ -11,6 +11,7 @@
# under the License.
from eventlet import tpool
import mock
from nova.compute import task_states
@ -83,6 +84,17 @@ class RbdTestCase(test.NoDBTestCase):
def tearDown(self):
super(RbdTestCase, self).tearDown()
@mock.patch.object(rbd_utils, 'rbd')
def test_rbdproxy_wraps_rbd(self, mock_rbd):
proxy = rbd_utils.RbdProxy()
self.assertIsInstance(proxy._rbd, tpool.Proxy)
@mock.patch.object(rbd_utils, 'rbd')
def test_rbdproxy_attribute_access_proxying(self, mock_rbd):
client = mock.MagicMock(ioctx='fake_ioctx')
rbd_utils.RbdProxy().list(client.ioctx)
mock_rbd.RBD.return_value.list.assert_called_once_with(client.ioctx)
def test_good_locations(self):
locations = ['rbd://fsid/pool/image/snap',
'rbd://%2F/%2F/%2F/%2F', ]

51
nova/virt/libvirt/storage/rbd_utils.py
View File

@ -41,6 +41,21 @@ from nova.virt.libvirt import utils as libvirt_utils
LOG = logging.getLogger(__name__)
class RbdProxy(object):
"""A wrapper around rbd.RBD class instance to avoid blocking of process.
Offloads all calls to rbd.RBD class methods to native OS threads, so that
we do not block the whole process while executing the librbd code.
"""
def __init__(self):
self._rbd = tpool.Proxy(rbd.RBD())
def __getattr__(self, attr):
return getattr(self._rbd, attr)
class RBDVolumeProxy(object):
"""Context manager for dealing with an existing rbd volume.
@ -55,9 +70,9 @@ class RBDVolumeProxy(object):
client, ioctx = driver._connect_to_rados(pool)
try:
snap_name = snapshot.encode('utf8') if snapshot else None
self.volume = rbd.Image(ioctx, name.encode('utf8'),
snapshot=snap_name,
read_only=read_only)
self.volume = tpool.Proxy(rbd.Image(ioctx, name.encode('utf8'),
snapshot=snap_name,
read_only=read_only))
except rbd.ImageNotFound:
with excutils.save_and_reraise_exception():
LOG.debug("rbd image %s does not exist", name)
@ -218,12 +233,12 @@ class RBDDriver(object):
with RADOSClient(self, str(pool)) as src_client:
with RADOSClient(self, dest_pool) as dest_client:
try:
rbd.RBD().clone(src_client.ioctx,
image.encode('utf-8'),
snapshot.encode('utf-8'),
dest_client.ioctx,
str(dest_name),
features=src_client.features)
RbdProxy().clone(src_client.ioctx,
image.encode('utf-8'),
snapshot.encode('utf-8'),
dest_client.ioctx,
str(dest_name),
features=src_client.features)
except rbd.PermissionError:
raise exception.Forbidden(_('no write permission on '
'storage pool %s') % dest_pool)
@ -266,7 +281,7 @@ class RBDDriver(object):
"""
LOG.debug('flattening %(pool)s/%(vol)s', dict(pool=pool, vol=volume))
with RBDVolumeProxy(self, str(volume), pool=pool) as vol:
tpool.execute(vol.flatten)
vol.flatten()
def exists(self, name, pool=None, snapshot=None):
try:
@ -285,7 +300,7 @@ class RBDDriver(object):
"""
with RADOSClient(self, self.pool) as client:
try:
rbd.RBD().remove(client.ioctx, name)
RbdProxy().remove(client.ioctx, name)
except rbd.ImageNotFound:
LOG.warning(_LW('image %(volume)s in pool %(pool)s can not be '
'found, failed to remove'),
@ -317,7 +332,7 @@ class RBDDriver(object):
"""
def _cleanup_vol(ioctx, volume, retryctx):
try:
rbd.RBD().remove(ioctx, volume)
RbdProxy().remove(ioctx, volume)
raise loopingcall.LoopingCallDone(retvalue=False)
except rbd.ImageHasSnapshots:
self.remove_snap(volume, libvirt_utils.RESIZE_SNAPSHOT_NAME,
@ -357,7 +372,7 @@ class RBDDriver(object):
else:
return disk.startswith(instance.uuid)
volumes = rbd.RBD().list(client.ioctx)
volumes = RbdProxy().list(client.ioctx)
for volume in filter(belongs_to_instance, volumes):
self._destroy_volume(client, volume)
@ -379,9 +394,9 @@ class RBDDriver(object):
LOG.debug('creating snapshot(%(snap)s) on rbd image(%(img)s)',
{'snap': name, 'img': volume})
with RBDVolumeProxy(self, str(volume), pool=pool) as vol:
tpool.execute(vol.create_snap, name)
vol.create_snap(name)
if protect and not vol.is_protected_snap(name):
tpool.execute(vol.protect_snap, name)
vol.protect_snap(name)
def remove_snap(self, volume, name, ignore_errors=False, pool=None,
force=False):
@ -397,7 +412,7 @@ class RBDDriver(object):
if name in [snap.get('name', '') for snap in vol.list_snaps()]:
if vol.is_protected_snap(name):
if force:
tpool.execute(vol.unprotect_snap, name)
vol.unprotect_snap(name)
elif not ignore_errors:
LOG.warning(_LW('snapshot(%(name)s) on rbd '
'image(%(img)s) is protected, '
@ -406,7 +421,7 @@ class RBDDriver(object):
return
LOG.debug('removing snapshot(%(name)s) on rbd image(%(img)s)',
{'name': name, 'img': volume})
tpool.execute(vol.remove_snap, name)
vol.remove_snap(name)
elif not ignore_errors:
LOG.warning(_LW('no snapshot(%(name)s) found on rbd '
'image(%(img)s)'),
@ -422,7 +437,7 @@ class RBDDriver(object):
if name in [snap.get('name', '') for snap in vol.list_snaps()]:
LOG.debug('rolling back rbd image(%(img)s) to '
'snapshot(%(snap)s)', {'snap': name, 'img': volume})
tpool.execute(vol.rollback_to_snap, name)
vol.rollback_to_snap(name)
else:
raise exception.SnapshotNotFound(snapshot_id=name)