nova/nova/virt/libvirt/imagebackend.py

673 lines
26 KiB
Python

# vim: tabstop=4 shiftwidth=4 softtabstop=4
# Copyright 2012 Grid Dynamics
# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import abc
import contextlib
import os
from oslo.config import cfg
from nova import exception
from nova.openstack.common import excutils
from nova.openstack.common import fileutils
from nova.openstack.common.gettextutils import _
from nova.openstack.common import jsonutils
from nova.openstack.common import log as logging
from nova import utils
from nova.virt.disk import api as disk
from nova.virt import images
from nova.virt.libvirt import config as vconfig
from nova.virt.libvirt import utils as libvirt_utils
try:
import rbd
except ImportError:
rbd = None
__imagebackend_opts = [
cfg.StrOpt('libvirt_images_type',
default='default',
help='VM Images format. Acceptable values are: raw, qcow2, lvm,'
'rbd, default. If default is specified,'
' then use_cow_images flag is used instead of this one.'),
cfg.StrOpt('libvirt_images_volume_group',
help='LVM Volume Group that is used for VM images, when you'
' specify libvirt_images_type=lvm.'),
cfg.BoolOpt('libvirt_sparse_logical_volumes',
default=False,
help='Create sparse logical volumes (with virtualsize)'
' if this flag is set to True.'),
cfg.IntOpt('libvirt_lvm_snapshot_size',
default=1000,
help='The amount of storage (in megabytes) to allocate for LVM'
' snapshot copy-on-write blocks.'),
cfg.StrOpt('libvirt_images_rbd_pool',
default='rbd',
help='the RADOS pool in which rbd volumes are stored'),
cfg.StrOpt('libvirt_images_rbd_ceph_conf',
default='', # default determined by librados
help='path to the ceph configuration file to use'),
]
CONF = cfg.CONF
CONF.register_opts(__imagebackend_opts)
CONF.import_opt('base_dir_name', 'nova.virt.libvirt.imagecache')
CONF.import_opt('preallocate_images', 'nova.virt.driver')
LOG = logging.getLogger(__name__)
class Image(object):
__metaclass__ = abc.ABCMeta
def __init__(self, source_type, driver_format, is_block_dev=False):
"""Image initialization.
:source_type: block or file
:driver_format: raw or qcow2
:is_block_dev:
"""
self.source_type = source_type
self.driver_format = driver_format
self.is_block_dev = is_block_dev
self.preallocate = False
# NOTE(dripton): We store lines of json (path, disk_format) in this
# file, for some image types, to prevent attacks based on changing the
# disk_format.
self.disk_info_path = None
# NOTE(mikal): We need a lock directory which is shared along with
# instance files, to cover the scenario where multiple compute nodes
# are trying to create a base file at the same time
self.lock_path = os.path.join(CONF.instances_path, 'locks')
@abc.abstractmethod
def create_image(self, prepare_template, base, size, *args, **kwargs):
"""Create image from template.
Contains specific behavior for each image type.
:prepare_template: function, that creates template.
Should accept `target` argument.
:base: Template name
:size: Size of created image in bytes
"""
pass
def libvirt_info(self, disk_bus, disk_dev, device_type, cache_mode,
extra_specs, hypervisor_version):
"""Get `LibvirtConfigGuestDisk` filled for this image.
:disk_dev: Disk bus device name
:disk_bus: Disk bus type
:device_type: Device type for this image.
:cache_mode: Caching mode for this image
:extra_specs: Instance type extra specs dict.
"""
info = vconfig.LibvirtConfigGuestDisk()
info.source_type = self.source_type
info.source_device = device_type
info.target_bus = disk_bus
info.target_dev = disk_dev
info.driver_cache = cache_mode
info.driver_format = self.driver_format
driver_name = libvirt_utils.pick_disk_driver_name(hypervisor_version,
self.is_block_dev)
info.driver_name = driver_name
info.source_path = self.path
tune_items = ['disk_read_bytes_sec', 'disk_read_iops_sec',
'disk_write_bytes_sec', 'disk_write_iops_sec',
'disk_total_bytes_sec', 'disk_total_iops_sec']
# Note(yaguang): Currently, the only tuning available is Block I/O
# throttling for qemu.
if self.source_type in ['file', 'block']:
for key, value in extra_specs.iteritems():
scope = key.split(':')
if len(scope) > 1 and scope[0] == 'quota':
if scope[1] in tune_items:
setattr(info, scope[1], value)
return info
def check_image_exists(self):
return os.path.exists(self.path)
def cache(self, fetch_func, filename, size=None, *args, **kwargs):
"""Creates image from template.
Ensures that template and image not already exists.
Ensures that base directory exists.
Synchronizes on template fetching.
:fetch_func: Function that creates the base image
Should accept `target` argument.
:filename: Name of the file in the image directory
:size: Size of created image in bytes (optional)
"""
@utils.synchronized(filename, external=True, lock_path=self.lock_path)
def call_if_not_exists(target, *args, **kwargs):
if not os.path.exists(target):
fetch_func(target=target, *args, **kwargs)
elif CONF.libvirt_images_type == "lvm" and \
'ephemeral_size' in kwargs:
fetch_func(target=target, *args, **kwargs)
base_dir = os.path.join(CONF.instances_path, CONF.base_dir_name)
if not os.path.exists(base_dir):
fileutils.ensure_tree(base_dir)
base = os.path.join(base_dir, filename)
if not self.check_image_exists() or not os.path.exists(base):
self.create_image(call_if_not_exists, base, size,
*args, **kwargs)
if (size and self.preallocate and self._can_fallocate() and
os.access(self.path, os.W_OK)):
utils.execute('fallocate', '-n', '-l', size, self.path)
def _can_fallocate(self):
"""Check once per class, whether fallocate(1) is available,
and that the instances directory supports fallocate(2).
"""
can_fallocate = getattr(self.__class__, 'can_fallocate', None)
if can_fallocate is None:
_out, err = utils.trycmd('fallocate', '-n', '-l', '1',
self.path + '.fallocate_test')
fileutils.delete_if_exists(self.path + '.fallocate_test')
can_fallocate = not err
self.__class__.can_fallocate = can_fallocate
if not can_fallocate:
LOG.error('Unable to preallocate_images=%s at path: %s' %
(CONF.preallocate_images, self.path))
return can_fallocate
@staticmethod
def verify_base_size(base, size, base_size=0):
"""Check that the base image is not larger than size.
Since images can't be generally shrunk, enforce this
constraint taking account of virtual image size.
"""
# Note(pbrady): The size and min_disk parameters of a glance
# image are checked against the instance size before the image
# is even downloaded from glance, but currently min_disk is
# adjustable and doesn't currently account for virtual disk size,
# so we need this extra check here.
# NOTE(cfb): Having a flavor that sets the root size to 0 and having
# nova effectively ignore that size and use the size of the
# image is considered a feature at this time, not a bug.
if size is None:
return
if size and not base_size:
base_size = disk.get_disk_size(base)
if size < base_size:
msg = _('%(base)s virtual size %(base_size)s '
'larger than flavor root disk size %(size)s')
LOG.error(msg % {'base': base,
'base_size': base_size,
'size': size})
raise exception.InstanceTypeDiskTooSmall()
def snapshot_create(self):
raise NotImplementedError()
def snapshot_extract(self, target, out_format):
raise NotImplementedError()
def snapshot_delete(self):
raise NotImplementedError()
def _get_driver_format(self):
return self.driver_format
def resolve_driver_format(self):
"""Return the driver format for self.path.
First checks self.disk_info_path for an entry.
If it's not there, calls self._get_driver_format(), and then
stores the result in self.disk_info_path
See https://bugs.launchpad.net/nova/+bug/1221190
"""
def _dict_from_line(line):
if not line:
return {}
try:
return jsonutils.loads(line)
except (TypeError, ValueError) as e:
msg = (_("Could not load line %(line)s, got error "
"%(error)s") %
{'line': line, 'error': unicode(e)})
raise exception.InvalidDiskInfo(reason=msg)
@utils.synchronized(self.disk_info_path, external=False,
lock_path=self.lock_path)
def write_to_disk_info_file():
# Use os.open to create it without group or world write permission.
fd = os.open(self.disk_info_path, os.O_RDWR | os.O_CREAT, 0o644)
with os.fdopen(fd, "r+") as disk_info_file:
line = disk_info_file.read().rstrip()
dct = _dict_from_line(line)
if self.path in dct:
msg = _("Attempted overwrite of an existing value.")
raise exception.InvalidDiskInfo(reason=msg)
dct.update({self.path: driver_format})
disk_info_file.seek(0)
disk_info_file.truncate()
disk_info_file.write('%s\n' % jsonutils.dumps(dct))
# Ensure the file is always owned by the nova user so qemu can't
# write it.
utils.chown(self.disk_info_path, owner_uid=os.getuid())
try:
if (self.disk_info_path is not None and
os.path.exists(self.disk_info_path)):
with open(self.disk_info_path) as disk_info_file:
line = disk_info_file.read().rstrip()
dct = _dict_from_line(line)
for path, driver_format in dct.iteritems():
if path == self.path:
return driver_format
driver_format = self._get_driver_format()
if self.disk_info_path is not None:
fileutils.ensure_tree(os.path.dirname(self.disk_info_path))
write_to_disk_info_file()
except OSError as e:
raise exception.DiskInfoReadWriteFail(reason=unicode(e))
return driver_format
class Raw(Image):
def __init__(self, instance=None, disk_name=None, path=None,
snapshot_name=None):
super(Raw, self).__init__("file", "raw", is_block_dev=False)
self.path = (path or
os.path.join(libvirt_utils.get_instance_path(instance),
disk_name))
self.snapshot_name = snapshot_name
self.preallocate = CONF.preallocate_images != 'none'
self.disk_info_path = os.path.join(os.path.dirname(self.path),
'disk.info')
self.correct_format()
def _get_driver_format(self):
data = images.qemu_img_info(self.path)
return data.file_format or 'raw'
def correct_format(self):
if os.path.exists(self.path):
self.driver_format = self.resolve_driver_format()
def create_image(self, prepare_template, base, size, *args, **kwargs):
@utils.synchronized(base, external=True, lock_path=self.lock_path)
def copy_raw_image(base, target, size):
libvirt_utils.copy_image(base, target)
if size:
# class Raw is misnamed, format may not be 'raw' in all cases
use_cow = self.driver_format == 'qcow2'
disk.extend(target, size, use_cow=use_cow)
generating = 'image_id' not in kwargs
if generating:
#Generating image in place
prepare_template(target=self.path, *args, **kwargs)
else:
prepare_template(target=base, max_size=size, *args, **kwargs)
self.verify_base_size(base, size)
if not os.path.exists(self.path):
with fileutils.remove_path_on_error(self.path):
copy_raw_image(base, self.path, size)
self.correct_format()
def snapshot_create(self):
pass
def snapshot_extract(self, target, out_format):
images.convert_image(self.path, target, out_format)
def snapshot_delete(self):
pass
class Qcow2(Image):
def __init__(self, instance=None, disk_name=None, path=None,
snapshot_name=None):
super(Qcow2, self).__init__("file", "qcow2", is_block_dev=False)
self.path = (path or
os.path.join(libvirt_utils.get_instance_path(instance),
disk_name))
self.snapshot_name = snapshot_name
self.preallocate = CONF.preallocate_images != 'none'
self.disk_info_path = os.path.join(os.path.dirname(self.path),
'disk.info')
self.resolve_driver_format()
def create_image(self, prepare_template, base, size, *args, **kwargs):
@utils.synchronized(base, external=True, lock_path=self.lock_path)
def copy_qcow2_image(base, target, size):
# TODO(pbrady): Consider copying the cow image here
# with preallocation=metadata set for performance reasons.
# This would be keyed on a 'preallocate_images' setting.
libvirt_utils.create_cow_image(base, target)
if size:
disk.extend(target, size, use_cow=True)
# Download the unmodified base image unless we already have a copy.
if not os.path.exists(base):
prepare_template(target=base, max_size=size, *args, **kwargs)
else:
self.verify_base_size(base, size)
legacy_backing_size = None
legacy_base = base
# Determine whether an existing qcow2 disk uses a legacy backing by
# actually looking at the image itself and parsing the output of the
# backing file it expects to be using.
if os.path.exists(self.path):
backing_path = libvirt_utils.get_disk_backing_file(self.path)
if backing_path is not None:
backing_file = os.path.basename(backing_path)
backing_parts = backing_file.rpartition('_')
if backing_file != backing_parts[-1] and \
backing_parts[-1].isdigit():
legacy_backing_size = int(backing_parts[-1])
legacy_base += '_%d' % legacy_backing_size
legacy_backing_size *= 1024 * 1024 * 1024
# Create the legacy backing file if necessary.
if legacy_backing_size:
if not os.path.exists(legacy_base):
with fileutils.remove_path_on_error(legacy_base):
libvirt_utils.copy_image(base, legacy_base)
disk.extend(legacy_base, legacy_backing_size, use_cow=True)
if not os.path.exists(self.path):
with fileutils.remove_path_on_error(self.path):
copy_qcow2_image(base, self.path, size)
def snapshot_create(self):
libvirt_utils.create_snapshot(self.path, self.snapshot_name)
def snapshot_extract(self, target, out_format):
libvirt_utils.extract_snapshot(self.path, 'qcow2',
self.snapshot_name, target,
out_format)
def snapshot_delete(self):
libvirt_utils.delete_snapshot(self.path, self.snapshot_name)
class Lvm(Image):
@staticmethod
def escape(filename):
return filename.replace('_', '__')
def __init__(self, instance=None, disk_name=None, path=None,
snapshot_name=None):
super(Lvm, self).__init__("block", "raw", is_block_dev=True)
if path:
info = libvirt_utils.logical_volume_info(path)
self.vg = info['VG']
self.lv = info['LV']
self.path = path
else:
if not CONF.libvirt_images_volume_group:
raise RuntimeError(_('You should specify'
' libvirt_images_volume_group'
' flag to use LVM images.'))
self.vg = CONF.libvirt_images_volume_group
self.lv = '%s_%s' % (self.escape(instance['name']),
self.escape(disk_name))
self.path = os.path.join('/dev', self.vg, self.lv)
# TODO(pbrady): possibly deprecate libvirt_sparse_logical_volumes
# for the more general preallocate_images
self.sparse = CONF.libvirt_sparse_logical_volumes
self.preallocate = not self.sparse
if snapshot_name:
self.snapshot_name = snapshot_name
self.snapshot_path = os.path.join('/dev', self.vg,
self.snapshot_name)
def _can_fallocate(self):
return False
def create_image(self, prepare_template, base, size, *args, **kwargs):
@utils.synchronized(base, external=True, lock_path=self.lock_path)
def create_lvm_image(base, size):
base_size = disk.get_disk_size(base)
self.verify_base_size(base, size, base_size=base_size)
resize = size > base_size
size = size if resize else base_size
libvirt_utils.create_lvm_image(self.vg, self.lv,
size, sparse=self.sparse)
images.convert_image(base, self.path, 'raw', run_as_root=True)
if resize:
disk.resize2fs(self.path, run_as_root=True)
generated = 'ephemeral_size' in kwargs
#Generate images with specified size right on volume
if generated and size:
libvirt_utils.create_lvm_image(self.vg, self.lv,
size, sparse=self.sparse)
with self.remove_volume_on_error(self.path):
prepare_template(target=self.path, *args, **kwargs)
else:
prepare_template(target=base, max_size=size, *args, **kwargs)
with self.remove_volume_on_error(self.path):
create_lvm_image(base, size)
@contextlib.contextmanager
def remove_volume_on_error(self, path):
try:
yield
except Exception:
with excutils.save_and_reraise_exception():
libvirt_utils.remove_logical_volumes(path)
def snapshot_create(self):
size = CONF.libvirt_lvm_snapshot_size
cmd = ('lvcreate', '-L', size, '-s', '--name', self.snapshot_name,
self.path)
libvirt_utils.execute(*cmd, run_as_root=True, attempts=3)
def snapshot_extract(self, target, out_format):
images.convert_image(self.snapshot_path, target, out_format,
run_as_root=True)
def snapshot_delete(self):
# NOTE (rmk): Snapshot volumes are automatically zeroed by LVM
cmd = ('lvremove', '-f', self.snapshot_path)
libvirt_utils.execute(*cmd, run_as_root=True, attempts=3)
class Rbd(Image):
def __init__(self, instance=None, disk_name=None, path=None,
snapshot_name=None, **kwargs):
super(Rbd, self).__init__("block", "rbd", is_block_dev=True)
if path:
try:
self.rbd_name = path.split('/')[1]
except IndexError:
raise exception.InvalidDevicePath(path=path)
else:
self.rbd_name = '%s_%s' % (instance['name'], disk_name)
self.snapshot_name = snapshot_name
if not CONF.libvirt_images_rbd_pool:
raise RuntimeError(_('You should specify'
' libvirt_images_rbd_pool'
' flag to use rbd images.'))
self.pool = CONF.libvirt_images_rbd_pool
self.ceph_conf = CONF.libvirt_images_rbd_ceph_conf
self.rbd = kwargs.get('rbd', rbd)
def _supports_layering(self):
return hasattr(self.rbd, 'RBD_FEATURE_LAYERING')
def _ceph_args(self):
args = []
args.extend(['--id', CONF.rbd_user])
args.extend(['--conf', self.ceph_conf])
return args
def _get_mon_addrs(self):
args = ['ceph', 'mon', 'dump', '--format=json'] + self._ceph_args()
out, _ = utils.execute(*args)
lines = out.split('\n')
if lines[0].startswith('dumped monmap epoch'):
lines = lines[1:]
monmap = jsonutils.loads('\n'.join(lines))
addrs = [mon['addr'] for mon in monmap['mons']]
hosts = []
ports = []
for addr in addrs:
host_port = addr[:addr.rindex('/')]
host, port = host_port.rsplit(':', 1)
hosts.append(host.strip('[]'))
ports.append(port)
return hosts, ports
def libvirt_info(self, disk_bus, disk_dev, device_type, cache_mode,
extra_specs, hypervisor_version):
"""Get `LibvirtConfigGuestDisk` filled for this image.
:disk_dev: Disk bus device name
:disk_bus: Disk bus type
:device_type: Device type for this image.
:cache_mode: Caching mode for this image
:extra_specs: Instance type extra specs dict.
"""
info = vconfig.LibvirtConfigGuestDisk()
hosts, ports = self._get_mon_addrs()
info.device_type = device_type
info.driver_format = 'raw'
info.driver_cache = cache_mode
info.target_bus = disk_bus
info.target_dev = disk_dev
info.source_type = 'network'
info.source_protocol = 'rbd'
info.source_name = '%s/%s' % (self.pool, self.rbd_name)
info.source_hosts = hosts
info.source_ports = ports
auth_enabled = (CONF.rbd_user is not None)
if CONF.rbd_secret_uuid:
info.auth_secret_uuid = CONF.rbd_secret_uuid
auth_enabled = True # Force authentication locally
if CONF.rbd_user:
info.auth_username = CONF.rbd_user
if auth_enabled:
info.auth_secret_type = 'ceph'
info.auth_secret_uuid = CONF.rbd_secret_uuid
return info
def _can_fallocate(self):
return False
def check_image_exists(self):
rbd_volumes = libvirt_utils.list_rbd_volumes(self.pool)
for vol in rbd_volumes:
if vol.startswith(self.rbd_name):
return True
return False
def create_image(self, prepare_template, base, size, *args, **kwargs):
if self.rbd is None:
raise RuntimeError(_('rbd python libraries not found'))
old_format = True
features = 0
if self._supports_layering():
old_format = False
features = self.rbd.RBD_FEATURE_LAYERING
if not os.path.exists(base):
prepare_template(target=base, max_size=size, *args, **kwargs)
else:
self.verify_base_size(base, size)
# keep using the command line import instead of librbd since it
# detects zeroes to preserve sparseness in the image
args = ['--pool', self.pool, base, self.rbd_name]
if self._supports_layering():
args += ['--new-format']
args += self._ceph_args()
libvirt_utils.import_rbd_image(*args)
def snapshot_create(self):
pass
def snapshot_extract(self, target, out_format):
snap = 'rbd:%s/%s' % (self.pool, self.rbd_name)
images.convert_image(snap, target, out_format)
def snapshot_delete(self):
pass
class Backend(object):
def __init__(self, use_cow):
self.BACKEND = {
'raw': Raw,
'qcow2': Qcow2,
'lvm': Lvm,
'rbd': Rbd,
'default': Qcow2 if use_cow else Raw
}
def backend(self, image_type=None):
if not image_type:
image_type = CONF.libvirt_images_type
image = self.BACKEND.get(image_type)
if not image:
raise RuntimeError(_('Unknown image_type=%s') % image_type)
return image
def image(self, instance, disk_name, image_type=None):
"""Constructs image for selected backend
:instance: Instance name.
:name: Image name.
:image_type: Image type.
Optional, is CONF.libvirt_images_type by default.
"""
backend = self.backend(image_type)
return backend(instance=instance, disk_name=disk_name)
def snapshot(self, disk_path, snapshot_name, image_type=None):
"""Returns snapshot for given image
:path: path to image
:snapshot_name: snapshot name
:image_type: type of image
"""
backend = self.backend(image_type)
return backend(path=disk_path, snapshot_name=snapshot_name)