# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# All Rights Reserved.
# Copyright (c) 2010 Citrix Systems, Inc.
# Copyright (c) 2011 Piston Cloud Computing, Inc
#
#    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.

"""
A connection to a hypervisor through libvirt.

Supports KVM, LXC, QEMU, UML, and XEN.

**Related Flags**

:libvirt_type:  Libvirt domain type.  Can be kvm, qemu, uml, xen
                (default: kvm).
:libvirt_uri:  Override for the default libvirt URI (depends on libvirt_type).
:libvirt_xml_template:  Libvirt XML Template.
:libvirt_disk_prefix:  Override the default disk prefix for the devices
                       attached to a server.
:rescue_image_id:  Rescue ami image (None = original image).
:rescue_kernel_id:  Rescue aki image (None = original image).
:rescue_ramdisk_id:  Rescue ari image (None = original image).
:injected_network_template:  Template file for injected network
:allow_same_net_traffic:  Whether to allow in project network traffic

"""

import hashlib
import functools
import multiprocessing
import os
import shutil
import sys
import tempfile
import uuid

from eventlet import greenthread
from xml.dom import minidom
from xml.etree import ElementTree

from nova.auth import manager
from nova import block_device
from nova.compute import instance_types
from nova.compute import power_state
from nova import context as nova_context
from nova import db
from nova import exception
from nova import flags
import nova.image
from nova import log as logging
from nova.openstack.common import cfg
from nova import network
from nova import utils
from nova.virt import driver
from nova.virt import images
from nova.virt.disk import api as disk
from nova.virt.libvirt import firewall
from nova.virt.libvirt import imagecache
from nova.virt.libvirt import utils as libvirt_utils


libvirt = None
Template = None


LOG = logging.getLogger(__name__)

libvirt_opts = [
    cfg.StrOpt('rescue_image_id',
               default=None,
               help='Rescue ami image'),
    cfg.StrOpt('rescue_kernel_id',
               default=None,
               help='Rescue aki image'),
    cfg.StrOpt('rescue_ramdisk_id',
               default=None,
               help='Rescue ari image'),
    cfg.StrOpt('libvirt_xml_template',
               default=utils.abspath('virt/libvirt.xml.template'),
               help='Libvirt XML Template'),
    cfg.StrOpt('libvirt_type',
               default='kvm',
               help='Libvirt domain type (valid options are: '
                    'kvm, lxc, qemu, uml, xen)'),
    cfg.StrOpt('libvirt_uri',
               default='',
               help='Override the default libvirt URI '
                    '(which is dependent on libvirt_type)'),
    cfg.BoolOpt('libvirt_inject_password',
                default=False,
                help='Inject the admin password at boot time, '
                     'without an agent.'),
    cfg.BoolOpt('use_usb_tablet',
                default=True,
                help='Sync virtual and real mouse cursors in Windows VMs'),
    cfg.StrOpt('cpuinfo_xml_template',
               default=utils.abspath('virt/cpuinfo.xml.template'),
               help='CpuInfo XML Template (Used only live migration now)'),
    cfg.StrOpt('live_migration_uri',
               default="qemu+tcp://%s/system",
               help='Define protocol used by live_migration feature'),
    cfg.StrOpt('live_migration_flag',
               default='VIR_MIGRATE_UNDEFINE_SOURCE, VIR_MIGRATE_PEER2PEER',
               help='Define live migration behavior.'),
    cfg.StrOpt('block_migration_flag',
               default='VIR_MIGRATE_UNDEFINE_SOURCE, VIR_MIGRATE_PEER2PEER, '
                       'VIR_MIGRATE_NON_SHARED_INC',
               help='Define block migration behavior.'),
    cfg.IntOpt('live_migration_bandwidth',
               default=0,
               help='Define live migration behavior'),
    cfg.StrOpt('snapshot_image_format',
               default=None,
               help='Snapshot image format (valid options are : '
                    'raw, qcow2, vmdk, vdi). '
                    'Defaults to same as source image'),
    cfg.StrOpt('libvirt_vif_type',
               default='bridge',
               help='Type of VIF to create.'),
    cfg.StrOpt('libvirt_vif_driver',
               default='nova.virt.libvirt.vif.LibvirtBridgeDriver',
               help='The libvirt VIF driver to configure the VIFs.'),
    cfg.ListOpt('libvirt_volume_drivers',
                default=[
                  'iscsi=nova.virt.libvirt.volume.LibvirtISCSIVolumeDriver',
                  'local=nova.virt.libvirt.volume.LibvirtVolumeDriver',
                  'fake=nova.virt.libvirt.volume.LibvirtFakeVolumeDriver',
                  'rbd=nova.virt.libvirt.volume.LibvirtNetVolumeDriver',
                  'sheepdog=nova.virt.libvirt.volume.LibvirtNetVolumeDriver'
                  ],
                help='Libvirt handlers for remote volumes.'),
    cfg.BoolOpt('libvirt_use_virtio_for_bridges',
                default=False,
                help='Use virtio for bridge interfaces'),
    cfg.StrOpt('libvirt_disk_prefix',
               default=None,
               help='Override the default disk prefix for the devices attached'
                    ' to a server, which is dependent on libvirt_type. '
                    '(valid options are: sd, xvd, uvd, vd)'),
    ]

FLAGS = flags.FLAGS
FLAGS.register_opts(libvirt_opts)

flags.DECLARE('live_migration_retry_count', 'nova.compute.manager')
flags.DECLARE('vncserver_proxyclient_address', 'nova.vnc')


def get_connection(read_only):
    # These are loaded late so that there's no need to install these
    # libraries when not using libvirt.
    # Cheetah is separate because the unit tests want to load Cheetah,
    # but not libvirt.
    global libvirt
    if libvirt is None:
        libvirt = __import__('libvirt')
    _late_load_cheetah()
    return LibvirtConnection(read_only)


def _late_load_cheetah():
    global Template
    if Template is None:
        t = __import__('Cheetah.Template', globals(), locals(),
                       ['Template'], -1)
        Template = t.Template


def _get_eph_disk(ephemeral):
    return 'disk.eph' + str(ephemeral['num'])


class LibvirtConnection(driver.ComputeDriver):

    def __init__(self, read_only):
        super(LibvirtConnection, self).__init__()

        self._host_state = None
        self._initiator = None
        self._wrapped_conn = None
        self.container = None
        self.read_only = read_only
        if FLAGS.firewall_driver not in firewall.drivers:
            FLAGS.set_default('firewall_driver', firewall.drivers[0])
        fw_class = utils.import_class(FLAGS.firewall_driver)
        self.firewall_driver = fw_class(get_connection=self._get_connection)
        self.vif_driver = utils.import_object(FLAGS.libvirt_vif_driver)
        self.volume_drivers = {}
        for driver_str in FLAGS.libvirt_volume_drivers:
            driver_type, _sep, driver = driver_str.partition('=')
            driver_class = utils.import_class(driver)
            self.volume_drivers[driver_type] = driver_class(self)
        self._host_state = None

        disk_prefix_map = {"lxc": "", "uml": "ubd", "xen": "sd"}
        if FLAGS.libvirt_disk_prefix:
            self._disk_prefix = FLAGS.libvirt_disk_prefix
        else:
            self._disk_prefix = disk_prefix_map.get(FLAGS.libvirt_type, 'vd')
        self.default_root_device = self._disk_prefix + 'a'
        self.default_second_device = self._disk_prefix + 'b'
        self.default_third_device = self._disk_prefix + 'c'

        self.image_cache_manager = imagecache.ImageCacheManager()

    @property
    def host_state(self):
        if not self._host_state:
            self._host_state = HostState(self.read_only)
        return self._host_state

    def init_host(self, host):
        # NOTE(nsokolov): moved instance restarting to ComputeManager
        pass

    @property
    def libvirt_xml(self):
        if not hasattr(self, '_libvirt_xml_cache_info'):
            self._libvirt_xml_cache_info = {}

        return utils.read_cached_file(FLAGS.libvirt_xml_template,
                self._libvirt_xml_cache_info)

    @property
    def cpuinfo_xml(self):
        if not hasattr(self, '_cpuinfo_xml_cache_info'):
            self._cpuinfo_xml_cache_info = {}

        return utils.read_cached_file(FLAGS.cpuinfo_xml_template,
                self._cpuinfo_xml_cache_info)

    def _get_connection(self):
        if not self._wrapped_conn or not self._test_connection():
            LOG.debug(_('Connecting to libvirt: %s'), self.uri)
            self._wrapped_conn = self._connect(self.uri,
                                               self.read_only)
        return self._wrapped_conn
    _conn = property(_get_connection)

    def _test_connection(self):
        try:
            self._wrapped_conn.getCapabilities()
            return True
        except libvirt.libvirtError as e:
            if (e.get_error_code() == libvirt.VIR_ERR_SYSTEM_ERROR and
                e.get_error_domain() in (libvirt.VIR_FROM_REMOTE,
                                         libvirt.VIR_FROM_RPC)):
                LOG.debug(_('Connection to libvirt broke'))
                return False
            raise

    @property
    def uri(self):
        if FLAGS.libvirt_type == 'uml':
            uri = FLAGS.libvirt_uri or 'uml:///system'
        elif FLAGS.libvirt_type == 'xen':
            uri = FLAGS.libvirt_uri or 'xen:///'
        elif FLAGS.libvirt_type == 'lxc':
            uri = FLAGS.libvirt_uri or 'lxc:///'
        else:
            uri = FLAGS.libvirt_uri or 'qemu:///system'
        return uri

    @staticmethod
    def _connect(uri, read_only):
        auth = [[libvirt.VIR_CRED_AUTHNAME, libvirt.VIR_CRED_NOECHOPROMPT],
                'root',
                None]

        if read_only:
            return libvirt.openReadOnly(uri)
        else:
            return libvirt.openAuth(uri, auth, 0)

    def get_num_instances(self):
        """Efficient override of base instance_exists method."""
        return self._conn.numOfDomains()

    def instance_exists(self, instance_id):
        """Efficient override of base instance_exists method."""
        try:
            _ignored = self._conn.lookupByName(instance_id)
            return True
        except libvirt.libvirtError:
            return False

    def list_instances(self):
        return [self._conn.lookupByID(x).name()
                for x in self._conn.listDomainsID()
                if x != 0]  # We skip domains with ID 0 (hypervisors).

    @staticmethod
    def _map_to_instance_info(domain):
        """Gets info from a virsh domain object into an InstanceInfo"""

        # domain.info() returns a list of:
        #    state:       one of the state values (virDomainState)
        #    maxMemory:   the maximum memory used by the domain
        #    memory:      the current amount of memory used by the domain
        #    nbVirtCPU:   the number of virtual CPU
        #    puTime:      the time used by the domain in nanoseconds

        (state, _max_mem, _mem, _num_cpu, _cpu_time) = domain.info()
        name = domain.name()

        return driver.InstanceInfo(name, state)

    def list_instances_detail(self):
        infos = []
        for domain_id in self._conn.listDomainsID():
            domain = self._conn.lookupByID(domain_id)
            info = self._map_to_instance_info(domain)
            infos.append(info)
        return infos

    def plug_vifs(self, instance, network_info):
        """Plug VIFs into networks."""
        for (network, mapping) in network_info:
            self.vif_driver.plug(instance, network, mapping)

    def unplug_vifs(self, instance, network_info):
        """Unplug VIFs from networks."""
        for (network, mapping) in network_info:
            self.vif_driver.unplug(instance, network, mapping)

    def _destroy(self, instance, network_info, block_device_info=None,
                 cleanup=True):
        instance_name = instance['name']

        try:
            virt_dom = self._lookup_by_name(instance_name)
        except exception.NotFound:
            virt_dom = None

        # If the instance is already terminated, we're still happy
        # Otherwise, destroy it
        if virt_dom is not None:
            try:
                virt_dom.destroy()
            except libvirt.libvirtError as e:
                is_okay = False
                errcode = e.get_error_code()
                if errcode == libvirt.VIR_ERR_OPERATION_INVALID:
                    # If the instance if already shut off, we get this:
                    # Code=55 Error=Requested operation is not valid:
                    # domain is not running
                    (state, _max_mem, _mem, _cpus, _t) = virt_dom.info()
                    if state == power_state.SHUTOFF:
                        is_okay = True

                if not is_okay:
                    LOG.warning(_("Error from libvirt during destroy. "
                                  "Code=%(errcode)s Error=%(e)s") %
                                locals(), instance=instance)
                    raise

            try:
                # NOTE(derekh): we can switch to undefineFlags and
                # VIR_DOMAIN_UNDEFINE_MANAGED_SAVE once we require 0.9.4
                if virt_dom.hasManagedSaveImage(0):
                    virt_dom.managedSaveRemove(0)
            except libvirt.libvirtError as e:
                errcode = e.get_error_code()
                LOG.warning(_("Error from libvirt during saved instance "
                              "removal. Code=%(errcode)s Error=%(e)s") %
                            locals(), instance=instance)

            try:
                # NOTE(justinsb): We remove the domain definition. We probably
                # would do better to keep it if cleanup=False (e.g. volumes?)
                # (e.g. #2 - not losing machines on failure)
                virt_dom.undefine()
            except libvirt.libvirtError as e:
                errcode = e.get_error_code()
                LOG.warning(_("Error from libvirt during undefine. "
                              "Code=%(errcode)s Error=%(e)s") %
                            locals(), instance=instance)
                raise

        self.unplug_vifs(instance, network_info)

        def _wait_for_destroy():
            """Called at an interval until the VM is gone."""
            instance_name = instance['name']

            try:
                state = self.get_info(instance_name)['state']
            except exception.NotFound:
                LOG.info(_("Instance destroyed successfully."),
                         instance=instance)
                raise utils.LoopingCallDone

        timer = utils.LoopingCall(_wait_for_destroy)
        timer.start(interval=0.5, now=True)

        self.firewall_driver.unfilter_instance(instance,
                                               network_info=network_info)

        # NOTE(vish): we disconnect from volumes regardless
        block_device_mapping = driver.block_device_info_get_mapping(
            block_device_info)
        for vol in block_device_mapping:
            connection_info = vol['connection_info']
            mountpoint = vol['mount_device']
            xml = self.volume_driver_method('disconnect_volume',
                                            connection_info,
                                            mountpoint)
        if cleanup:
            self._cleanup(instance)

        return True

    def destroy(self, instance, network_info, block_device_info=None):
        return self._destroy(instance, network_info, block_device_info,
                             cleanup=True)

    def _cleanup(self, instance):
        target = os.path.join(FLAGS.instances_path, instance['name'])
        instance_name = instance['name']
        LOG.info(_('Deleting instance files %(target)s') % locals(),
                 instance=instance)
        if FLAGS.libvirt_type == 'lxc':
            disk.destroy_container(self.container)
        if os.path.exists(target):
            shutil.rmtree(target)

    def get_volume_connector(self, instance):
        if not self._initiator:
            self._initiator = libvirt_utils.get_iscsi_initiator()
            if not self._initiator:
                LOG.warn(_('Could not determine iscsi initiator name'),
                         instance=instance)
        return {
            'ip': FLAGS.my_ip,
            'initiator': self._initiator,
        }

    def _cleanup_resize(self, instance):
        target = os.path.join(FLAGS.instances_path,
                              instance['name'] + "_resize")
        if os.path.exists(target):
            shutil.rmtree(target)

    def volume_driver_method(self, method_name, connection_info,
                             *args, **kwargs):
        driver_type = connection_info.get('driver_volume_type')
        if not driver_type in self.volume_drivers:
            raise exception.VolumeDriverNotFound(driver_type=driver_type)
        driver = self.volume_drivers[driver_type]
        method = getattr(driver, method_name)
        return method(connection_info, *args, **kwargs)

    @exception.wrap_exception()
    def attach_volume(self, connection_info, instance_name, mountpoint):
        virt_dom = self._lookup_by_name(instance_name)
        mount_device = mountpoint.rpartition("/")[2]
        xml = self.volume_driver_method('connect_volume',
                                        connection_info,
                                        mount_device)

        if FLAGS.libvirt_type == 'lxc':
            self._attach_lxc_volume(xml, virt_dom, instance_name)
        else:
            virt_dom.attachDevice(xml)

    @staticmethod
    def _get_disk_xml(xml, device):
        """Returns the xml for the disk mounted at device"""
        try:
            doc = ElementTree.fromstring(xml)
        except Exception:
            return None
        ret = doc.findall('./devices/disk')
        for node in ret:
            for child in node.getchildren():
                if child.tag == 'target':
                    if child.get('dev') == device:
                        return ElementTree.tostring(node)

    @exception.wrap_exception()
    def detach_volume(self, connection_info, instance_name, mountpoint):
        mount_device = mountpoint.rpartition("/")[2]
        try:
            # NOTE(vish): This is called to cleanup volumes after live
            #             migration, so we should still logout even if
            #             the instance doesn't exist here anymore.
            virt_dom = self._lookup_by_name(instance_name)
            xml = self._get_disk_xml(virt_dom.XMLDesc(0), mount_device)
            if not xml:
                raise exception.DiskNotFound(location=mount_device)
            if FLAGS.libvirt_type == 'lxc':
                self._detach_lxc_volume(xml, virt_dom, instance_name)
            else:
                virt_dom.detachDevice(xml)
        finally:
            self.volume_driver_method('disconnect_volume',
                                      connection_info,
                                      mount_device)

    @exception.wrap_exception()
    def _attach_lxc_volume(self, xml, virt_dom, instance_name):
        LOG.info(_('attaching LXC block device'))

        lxc_container_root = self.get_lxc_container_root(virt_dom)
        lxc_host_volume = self.get_lxc_host_device(xml)
        lxc_container_device = self.get_lxc_container_target(xml)
        lxc_container_target = "%s/%s" % (lxc_container_root,
                                          lxc_container_device)

        if lxc_container_target:
            disk.bind(lxc_host_volume, lxc_container_target, instance_name)

    @exception.wrap_exception()
    def _detach_lxc_volume(self, xml, virt_dom, instance_name):
        LOG.info(_('detaching LXC block device'))

        lxc_container_root = self.get_lxc_container_root(virt_dom)
        lxc_host_volume = self.get_lxc_host_device(xml)
        lxc_container_device = self.get_lxc_container_target(xml)
        lxc_container_target = "%s/%s" % (lxc_container_root,
                                          lxc_container_device)

        if lxc_container_target:
            disk.unbind(lxc_container_target)

    @staticmethod
    def get_lxc_container_root(virt_dom):
        xml = virt_dom.XMLDesc(0)
        doc = ElementTree.fromstring(xml)
        filesystem_block = doc.findall('./devices/filesystem')
        for cnt, filesystem_nodes in enumerate(filesystem_block):
            return filesystem_nodes[cnt].get('dir')

    @staticmethod
    def get_lxc_host_device(xml):
        dom = minidom.parseString(xml)

        for device in dom.getElementsByTagName('source'):
            return device.getAttribute('dev')

    @staticmethod
    def get_lxc_container_target(xml):
        dom = minidom.parseString(xml)

        for device in dom.getElementsByTagName('target'):
            filesystem = device.getAttribute('dev')
            return 'dev/%s' % filesystem

    @exception.wrap_exception()
    def snapshot(self, context, instance, image_href):
        """Create snapshot from a running VM instance.

        This command only works with qemu 0.14+
        """
        try:
            virt_dom = self._lookup_by_name(instance['name'])
        except exception.InstanceNotFound:
            raise exception.InstanceNotRunning()

        (image_service, image_id) = nova.image.get_image_service(
            context, instance['image_ref'])
        base = image_service.show(context, image_id)
        _image_service = nova.image.get_image_service(context, image_href)
        snapshot_image_service, snapshot_image_id = _image_service
        snapshot = snapshot_image_service.show(context, snapshot_image_id)

        metadata = {'is_public': False,
                    'status': 'active',
                    'name': snapshot['name'],
                    'properties': {
                                   'kernel_id': instance['kernel_id'],
                                   'image_location': 'snapshot',
                                   'image_state': 'available',
                                   'owner_id': instance['project_id'],
                                   'ramdisk_id': instance['ramdisk_id'],
                                   }
                    }
        if 'architecture' in base['properties']:
            arch = base['properties']['architecture']
            metadata['properties']['architecture'] = arch

        source_format = base.get('disk_format') or 'raw'
        if source_format == 'ami':
            # NOTE(vish): assume amis are raw
            source_format = 'raw'
        image_format = FLAGS.snapshot_image_format or source_format
        if FLAGS.use_cow_images:
            source_format = 'qcow2'
        # NOTE(vish): glance forces ami disk format to be ami
        if base.get('disk_format') == 'ami':
            metadata['disk_format'] = 'ami'
        else:
            metadata['disk_format'] = image_format

        if 'container_format' in base:
            metadata['container_format'] = base['container_format']

        # Make the snapshot
        snapshot_name = uuid.uuid4().hex
        snapshot_xml = """
        <domainsnapshot>
            <name>%s</name>
        </domainsnapshot>
        """ % snapshot_name
        snapshot_ptr = virt_dom.snapshotCreateXML(snapshot_xml, 0)

        # Find the disk
        xml_desc = virt_dom.XMLDesc(0)
        domain = ElementTree.fromstring(xml_desc)
        source = domain.find('devices/disk/source')
        disk_path = source.get('file')

        # Export the snapshot to a raw image
        temp_dir = tempfile.mkdtemp()
        try:
            out_path = os.path.join(temp_dir, snapshot_name)
            libvirt_utils.extract_snapshot(disk_path, source_format,
                                           snapshot_name, out_path,
                                           image_format)
            # Upload that image to the image service
            with libvirt_utils.file_open(out_path) as image_file:
                image_service.update(context,
                                     image_href,
                                     metadata,
                                     image_file)

        finally:
            # Clean up
            shutil.rmtree(temp_dir)
            snapshot_ptr.delete(0)

    @exception.wrap_exception()
    def reboot(self, instance, network_info, reboot_type=None, xml=None):
        """Reboot a virtual machine, given an instance reference.

        This method actually destroys and re-creates the domain to ensure the
        reboot happens, as the guest OS cannot ignore this action.

        """

        virt_dom = self._conn.lookupByName(instance['name'])
        # NOTE(itoumsn): Use XML delived from the running instance
        # instead of using to_xml(instance, network_info). This is almost
        # the ultimate stupid workaround.
        if not xml:
            xml = virt_dom.XMLDesc(0)

        # NOTE(itoumsn): self.shutdown() and wait instead of self.destroy() is
        # better because we cannot ensure flushing dirty buffers
        # in the guest OS. But, in case of KVM, shutdown() does not work...
        self._destroy(instance, network_info, cleanup=False)
        self.unplug_vifs(instance, network_info)
        self.plug_vifs(instance, network_info)
        self.firewall_driver.setup_basic_filtering(instance, network_info)
        self.firewall_driver.prepare_instance_filter(instance, network_info)
        self._create_new_domain(xml)
        self.firewall_driver.apply_instance_filter(instance, network_info)

        def _wait_for_reboot():
            """Called at an interval until the VM is running again."""
            instance_name = instance['name']

            try:
                state = self.get_info(instance_name)['state']
            except exception.NotFound:
                LOG.error(_("During reboot, instance disappeared."),
                          instance=instance)
                raise utils.LoopingCallDone

            if state == power_state.RUNNING:
                LOG.info(_("Instance rebooted successfully."),
                         instance=instance)
                raise utils.LoopingCallDone

        timer = utils.LoopingCall(_wait_for_reboot)
        return timer.start(interval=0.5, now=True)

    @exception.wrap_exception()
    def pause(self, instance):
        """Pause VM instance"""
        dom = self._lookup_by_name(instance.name)
        dom.suspend()

    @exception.wrap_exception()
    def unpause(self, instance):
        """Unpause paused VM instance"""
        dom = self._lookup_by_name(instance.name)
        dom.resume()

    @exception.wrap_exception()
    def suspend(self, instance):
        """Suspend the specified instance"""
        dom = self._lookup_by_name(instance.name)
        dom.managedSave(0)

    @exception.wrap_exception()
    def resume(self, instance):
        """resume the specified instance"""
        dom = self._lookup_by_name(instance.name)
        dom.create()

    @exception.wrap_exception()
    def rescue(self, context, instance, network_info, image_meta):
        """Loads a VM using rescue images.

        A rescue is normally performed when something goes wrong with the
        primary images and data needs to be corrected/recovered. Rescuing
        should not edit or over-ride the original image, only allow for
        data recovery.

        """

        virt_dom = self._conn.lookupByName(instance['name'])
        unrescue_xml = virt_dom.XMLDesc(0)
        unrescue_xml_path = os.path.join(FLAGS.instances_path,
                                         instance['name'],
                                         'unrescue.xml')
        libvirt_utils.write_to_file(unrescue_xml_path, unrescue_xml)

        xml = self.to_xml(instance, network_info, image_meta, rescue=True)
        rescue_images = {
            'image_id': FLAGS.rescue_image_id or instance['image_ref'],
            'kernel_id': FLAGS.rescue_kernel_id or instance['kernel_id'],
            'ramdisk_id': FLAGS.rescue_ramdisk_id or instance['ramdisk_id'],
        }
        self._create_image(context, instance, xml, '.rescue', rescue_images,
                           network_info=network_info)
        self.reboot(instance, network_info, xml=xml)

    @exception.wrap_exception()
    def unrescue(self, instance, network_info):
        """Reboot the VM which is being rescued back into primary images.

        Because reboot destroys and re-creates instances, unresue should
        simply call reboot.

        """
        unrescue_xml_path = os.path.join(FLAGS.instances_path,
                                         instance['name'],
                                         'unrescue.xml')
        unrescue_xml = libvirt_utils.load_file(unrescue_xml_path)
        libvirt_utils.file_delete(unrescue_xml_path)
        self.reboot(instance, network_info, xml=unrescue_xml)

    @exception.wrap_exception()
    def poll_rebooting_instances(self, timeout):
        pass

    @exception.wrap_exception()
    def poll_rescued_instances(self, timeout):
        pass

    @exception.wrap_exception()
    def poll_unconfirmed_resizes(self, resize_confirm_window):
        """Poll for unconfirmed resizes.

        Look for any unconfirmed resizes that are older than
        `resize_confirm_window` and automatically confirm them.
        """
        ctxt = nova_context.get_admin_context()
        migrations = db.migration_get_all_unconfirmed(ctxt,
            resize_confirm_window)

        migrations_info = dict(migration_count=len(migrations),
                confirm_window=FLAGS.resize_confirm_window)

        if migrations_info["migration_count"] > 0:
            LOG.info(_("Found %(migration_count)d unconfirmed migrations "
                    "older than %(confirm_window)d seconds") % migrations_info)

        for migration in migrations:
            LOG.info(_("Automatically confirming migration %d"), migration.id)
            self.compute_api.confirm_resize(ctxt, migration.instance_uuid)

    def _enable_hairpin(self, instance):
        interfaces = self.get_interfaces(instance['name'])
        for interface in interfaces:
            utils.execute('tee',
                          '/sys/class/net/%s/brport/hairpin_mode' % interface,
                          '>',
                          '/dev/null',
                          process_input='1',
                          run_as_root=True,
                          check_exit_code=[0, 1])

    # NOTE(ilyaalekseyev): Implementation like in multinics
    # for xenapi(tr3buchet)
    @exception.wrap_exception()
    def spawn(self, context, instance, image_meta, network_info,
              block_device_info=None):
        xml = self.to_xml(instance, network_info, image_meta, False,
                          block_device_info=block_device_info)
        self.firewall_driver.setup_basic_filtering(instance, network_info)
        self.firewall_driver.prepare_instance_filter(instance, network_info)
        self._create_image(context, instance, xml, network_info=network_info,
                           block_device_info=block_device_info)

        domain = self._create_new_domain(xml)
        LOG.debug(_("Instance is running"), instance=instance)
        self._enable_hairpin(instance)
        self.firewall_driver.apply_instance_filter(instance, network_info)

        def _wait_for_boot():
            """Called at an interval until the VM is running."""
            instance_name = instance['name']

            try:
                state = self.get_info(instance_name)['state']
            except exception.NotFound:
                LOG.error(_("During reboot, instance disappeared."),
                          instance=instance)
                raise utils.LoopingCallDone

            if state == power_state.RUNNING:
                LOG.info(_("Instance spawned successfully."),
                         instance=instance)
                raise utils.LoopingCallDone

        timer = utils.LoopingCall(_wait_for_boot)
        return timer.start(interval=0.5, now=True)

    def _flush_xen_console(self, virsh_output):
        LOG.info(_('virsh said: %r'), virsh_output)
        virsh_output = virsh_output[0].strip()

        if virsh_output.startswith('/dev/'):
            LOG.info(_("cool, it's a device"))
            out, err = utils.execute('dd',
                                     'if=%s' % virsh_output,
                                     'iflag=nonblock',
                                     run_as_root=True,
                                     check_exit_code=False)
            return out
        else:
            return ''

    def _append_to_file(self, data, fpath):
        LOG.info(_('data: %(data)r, fpath: %(fpath)r') % locals())
        fp = open(fpath, 'a+')
        fp.write(data)
        return fpath

    def _inject_files(self, instance, files, partition):
        disk_path = os.path.join(FLAGS.instances_path,
                                 instance['name'], 'disk')
        disk.inject_files(disk_path, files, partition=partition,
                          use_cow=FLAGS.use_cow_images)

    @exception.wrap_exception()
    def get_console_output(self, instance):
        console_log = os.path.join(FLAGS.instances_path, instance['name'],
                                   'console.log')

        libvirt_utils.chown(console_log, os.getuid())

        if FLAGS.libvirt_type == 'xen':
            # Xen is special
            virsh_output = utils.execute('virsh',
                                         'ttyconsole',
                                         instance['name'])
            data = self._flush_xen_console(virsh_output)
            fpath = self._append_to_file(data, console_log)
        elif FLAGS.libvirt_type == 'lxc':
            # LXC is also special
            LOG.info(_("Unable to read LXC console"), instance=instance)
        else:
            fpath = console_log

        return libvirt_utils.load_file(fpath)

    @staticmethod
    def get_host_ip_addr():
        return FLAGS.my_ip

    @exception.wrap_exception()
    def get_vnc_console(self, instance):
        def get_vnc_port_for_instance(instance_name):
            virt_dom = self._lookup_by_name(instance_name)
            xml = virt_dom.XMLDesc(0)
            # TODO: use etree instead of minidom
            dom = minidom.parseString(xml)

            for graphic in dom.getElementsByTagName('graphics'):
                if graphic.getAttribute('type') == 'vnc':
                    return graphic.getAttribute('port')

        port = get_vnc_port_for_instance(instance['name'])
        host = FLAGS.vncserver_proxyclient_address

        return {'host': host, 'port': port, 'internal_access_path': None}

    @staticmethod
    def _cache_image(fn, target, fname, cow=False, size=None, *args, **kwargs):
        """Wrapper for a method that creates an image that caches the image.

        This wrapper will save the image into a common store and create a
        copy for use by the hypervisor.

        The underlying method should specify a kwarg of target representing
        where the image will be saved.

        fname is used as the filename of the base image.  The filename needs
        to be unique to a given image.

        If cow is True, it will make a CoW image instead of a copy.

        If size is specified, we attempt to resize up to that size.
        """

        generating = 'image_id' not in kwargs
        if not os.path.exists(target):
            base_dir = os.path.join(FLAGS.instances_path, '_base')
            if not os.path.exists(base_dir):
                libvirt_utils.ensure_tree(base_dir)
            base = os.path.join(base_dir, fname)

            @utils.synchronized(fname)
            def call_if_not_exists(base, fn, *args, **kwargs):
                if not os.path.exists(base):
                    fn(target=base, *args, **kwargs)

            if cow or not generating:
                call_if_not_exists(base, fn, *args, **kwargs)
            elif generating:
                # For raw it's quicker to just generate outside the cache
                call_if_not_exists(target, fn, *args, **kwargs)

            if cow:
                cow_base = base
                if size:
                    size_gb = size / (1024 * 1024 * 1024)
                    cow_base += "_%d" % size_gb
                    if not os.path.exists(cow_base):
                        libvirt_utils.copy_image(base, cow_base)
                        disk.extend(cow_base, size)
                libvirt_utils.create_cow_image(cow_base, target)
            elif not generating:
                libvirt_utils.copy_image(base, target)
                # Resize after the copy, as it's usually much faster
                # to make sparse updates, rather than potentially
                # naively copying the whole image file.
                if size:
                    disk.extend(target, size)

    @staticmethod
    def _create_local(target, local_size, unit='G', fs_format=None):
        """Create a blank image of specified size"""

        if not fs_format:
            fs_format = FLAGS.default_ephemeral_format

        libvirt_utils.create_image('raw', target,
                                   '%d%c' % (local_size, unit))
        if fs_format:
            libvirt_utils.mkfs(fs_format, target)

    def _create_ephemeral(self, target, ephemeral_size, fs_label, os_type):
        self._create_local(target, ephemeral_size)
        disk.mkfs(os_type, fs_label, target)

    @staticmethod
    def _create_swap(target, swap_mb):
        """Create a swap file of specified size"""
        libvirt_utils.create_image('raw', target, '%dM' % swap_mb)
        libvirt_utils.mkfs('swap', target)

    def _create_image(self, context, instance, libvirt_xml, suffix='',
                      disk_images=None, network_info=None,
                      block_device_info=None):
        if not suffix:
            suffix = ''

        # syntactic nicety
        def basepath(fname='', suffix=suffix):
            return os.path.join(FLAGS.instances_path,
                                instance['name'],
                                fname + suffix)

        # ensure directories exist and are writable
        libvirt_utils.ensure_tree(basepath(suffix=''))

        LOG.info(_('Creating image'), instance=instance)
        libvirt_utils.write_to_file(basepath('libvirt.xml'), libvirt_xml)

        if FLAGS.libvirt_type == 'lxc':
            container_dir = '%s/rootfs' % basepath(suffix='')
            libvirt_utils.ensure_tree(container_dir)

        # NOTE(vish): No need add the suffix to console.log
        libvirt_utils.write_to_file(basepath('console.log', ''), '', 007)

        if not disk_images:
            disk_images = {'image_id': instance['image_ref'],
                           'kernel_id': instance['kernel_id'],
                           'ramdisk_id': instance['ramdisk_id']}

        if disk_images['kernel_id']:
            fname = disk_images['kernel_id']
            self._cache_image(fn=libvirt_utils.fetch_image,
                              context=context,
                              target=basepath('kernel'),
                              fname=fname,
                              image_id=disk_images['kernel_id'],
                              user_id=instance['user_id'],
                              project_id=instance['project_id'])
            if disk_images['ramdisk_id']:
                fname = disk_images['ramdisk_id']
                self._cache_image(fn=libvirt_utils.fetch_image,
                                  context=context,
                                  target=basepath('ramdisk'),
                                  fname=fname,
                                  image_id=disk_images['ramdisk_id'],
                                  user_id=instance['user_id'],
                                  project_id=instance['project_id'])

        root_fname = hashlib.sha1(str(disk_images['image_id'])).hexdigest()
        size = instance['root_gb'] * 1024 * 1024 * 1024

        inst_type_id = instance['instance_type_id']
        inst_type = instance_types.get_instance_type(inst_type_id)
        if size == 0 or suffix == '.rescue':
            size = None

        if not self._volume_in_mapping(self.default_root_device,
                                       block_device_info):
            self._cache_image(fn=libvirt_utils.fetch_image,
                              context=context,
                              target=basepath('disk'),
                              fname=root_fname,
                              cow=FLAGS.use_cow_images,
                              image_id=disk_images['image_id'],
                              user_id=instance['user_id'],
                              project_id=instance['project_id'],
                              size=size)

        ephemeral_gb = instance['ephemeral_gb']
        if ephemeral_gb and not self._volume_in_mapping(
                self.default_second_device, block_device_info):
            swap_device = self.default_third_device
            fn = functools.partial(self._create_ephemeral,
                                   fs_label='ephemeral0',
                                   os_type=instance.os_type)
            self._cache_image(fn=fn,
                              target=basepath('disk.local'),
                              fname="ephemeral_%s_%s_%s" %
                              ("0", ephemeral_gb, instance.os_type),
                              cow=FLAGS.use_cow_images,
                              ephemeral_size=ephemeral_gb)
        else:
            swap_device = self.default_second_device

        for eph in driver.block_device_info_get_ephemerals(block_device_info):
            fn = functools.partial(self._create_ephemeral,
                                   fs_label='ephemeral%d' % eph['num'],
                                   os_type=instance.os_type)
            self._cache_image(fn=fn,
                              target=basepath(_get_eph_disk(eph)),
                              fname="ephemeral_%s_%s_%s" %
                              (eph['num'], eph['size'], instance.os_type),
                              cow=FLAGS.use_cow_images,
                              ephemeral_size=eph['size'])

        swap_mb = 0

        swap = driver.block_device_info_get_swap(block_device_info)
        if driver.swap_is_usable(swap):
            swap_mb = swap['swap_size']
        elif (inst_type['swap'] > 0 and
              not self._volume_in_mapping(swap_device, block_device_info)):
            swap_mb = inst_type['swap']

        if swap_mb > 0:
            self._cache_image(fn=self._create_swap,
                              target=basepath('disk.swap'),
                              fname="swap_%s" % swap_mb,
                              cow=FLAGS.use_cow_images,
                              swap_mb=swap_mb)

        # For now, we assume that if we're not using a kernel, we're using a
        # partitioned disk image where the target partition is the first
        # partition
        target_partition = None
        if not instance['kernel_id']:
            target_partition = "1"

        config_drive_id = instance.get('config_drive_id')
        config_drive = instance.get('config_drive')

        if any((FLAGS.libvirt_type == 'lxc', config_drive, config_drive_id)):
            target_partition = None

        if config_drive_id:
            fname = config_drive_id
            self._cache_image(fn=libvirt_utils.fetch_image,
                              target=basepath('disk.config'),
                              fname=fname,
                              image_id=config_drive_id,
                              user_id=instance['user_id'],
                              project_id=instance['project_id'],)
        elif config_drive:
            self._create_local(basepath('disk.config'), 64, unit='M',
                               fs_format='msdos')  # 64MB

        if instance['key_data']:
            key = str(instance['key_data'])
        else:
            key = None
        net = None

        nets = []
        ifc_template = open(FLAGS.injected_network_template).read()
        ifc_num = -1
        have_injected_networks = False
        admin_context = nova_context.get_admin_context()
        for (network_ref, mapping) in network_info:
            ifc_num += 1

            if not network_ref['injected']:
                continue

            have_injected_networks = True
            address = mapping['ips'][0]['ip']
            netmask = mapping['ips'][0]['netmask']
            address_v6 = None
            gateway_v6 = None
            netmask_v6 = None
            if FLAGS.use_ipv6:
                address_v6 = mapping['ip6s'][0]['ip']
                netmask_v6 = mapping['ip6s'][0]['netmask']
                gateway_v6 = mapping['gateway_v6']
            net_info = {'name': 'eth%d' % ifc_num,
                   'address': address,
                   'netmask': netmask,
                   'gateway': mapping['gateway'],
                   'broadcast': mapping['broadcast'],
                   'dns': ' '.join(mapping['dns']),
                   'address_v6': address_v6,
                   'gateway_v6': gateway_v6,
                   'netmask_v6': netmask_v6}
            nets.append(net_info)

        if have_injected_networks:
            net = str(Template(ifc_template,
                               searchList=[{'interfaces': nets,
                                            'use_ipv6': FLAGS.use_ipv6}]))

        metadata = instance.get('metadata')

        if FLAGS.libvirt_inject_password:
            admin_password = instance.get('admin_pass')
        else:
            admin_password = None

        if any((key, net, metadata, admin_password)):

            instance_name = instance['name']

            if config_drive:  # Should be True or None by now.
                injection_path = basepath('disk.config')
                img_id = 'config-drive'
            else:
                injection_path = basepath('disk')
                img_id = instance.image_ref

            for injection in ('metadata', 'key', 'net', 'admin_password'):
                if locals()[injection]:
                    LOG.info(_('Injecting %(injection)s into image %(img_id)s'
                               % locals()), instance=instance)
            try:
                disk.inject_data(injection_path,
                                 key, net, metadata, admin_password,
                                 partition=target_partition,
                                 use_cow=FLAGS.use_cow_images)

            except Exception as e:
                # This could be a windows image, or a vmdk format disk
                LOG.warn(_('Ignoring error injecting data into image '
                           '%(img_id)s (%(e)s)') % locals(),
                         instance=instance)

        if FLAGS.libvirt_type == 'lxc':
            self.container = disk.setup_container(basepath('disk'),
                                                  container_dir=container_dir,
                                                  use_cow=FLAGS.use_cow_images)

        if FLAGS.libvirt_type == 'uml':
            libvirt_utils.chown(basepath('disk'), 'root')

        files_to_inject = instance.get('injected_files')
        if files_to_inject:
            self._inject_files(instance, files_to_inject,
                               partition=target_partition)

    @staticmethod
    def _volume_in_mapping(mount_device, block_device_info):
        block_device_list = [block_device.strip_dev(vol['mount_device'])
                             for vol in
                             driver.block_device_info_get_mapping(
                                 block_device_info)]
        swap = driver.block_device_info_get_swap(block_device_info)
        if driver.swap_is_usable(swap):
            block_device_list.append(
                block_device.strip_dev(swap['device_name']))
        block_device_list += [block_device.strip_dev(ephemeral['device_name'])
                              for ephemeral in
                              driver.block_device_info_get_ephemerals(
                                  block_device_info)]

        LOG.debug(_("block_device_list %s"), block_device_list)
        return block_device.strip_dev(mount_device) in block_device_list

    def _prepare_xml_info(self, instance, network_info, image_meta, rescue,
                          block_device_info=None):
        block_device_mapping = driver.block_device_info_get_mapping(
            block_device_info)

        nics = []
        for (network, mapping) in network_info:
            nics.append(self.vif_driver.plug(instance, network, mapping))
        # FIXME(vish): stick this in db
        inst_type_id = instance['instance_type_id']
        inst_type = instance_types.get_instance_type(inst_type_id)

        if FLAGS.use_cow_images:
            driver_type = 'qcow2'
        else:
            driver_type = 'raw'

        if image_meta and image_meta.get('disk_format') == 'iso':
            root_device_type = 'cdrom'
        else:
            root_device_type = 'disk'

        volumes = []
        for vol in block_device_mapping:
            connection_info = vol['connection_info']
            mountpoint = vol['mount_device']
            xml = self.volume_driver_method('connect_volume',
                                            connection_info,
                                            mountpoint)
            volumes.append(xml)

        ebs_root = self._volume_in_mapping(self.default_root_device,
                                           block_device_info)

        ephemeral_device = False
        if not (self._volume_in_mapping(self.default_second_device,
                                        block_device_info) or
                0 in [eph['num'] for eph in
                      driver.block_device_info_get_ephemerals(
                          block_device_info)]):
            if instance['ephemeral_gb'] > 0:
                ephemeral_device = self.default_second_device

        ephemerals = []
        for eph in driver.block_device_info_get_ephemerals(block_device_info):
            ephemerals.append({'device_path': _get_eph_disk(eph),
                               'device': block_device.strip_dev(
                                   eph['device_name'])})

        xml_info = {'type': FLAGS.libvirt_type,
                    'name': instance['name'],
                    'uuid': instance['uuid'],
                    'basepath': os.path.join(FLAGS.instances_path,
                                             instance['name']),
                    'memory_kb': inst_type['memory_mb'] * 1024,
                    'vcpus': inst_type['vcpus'],
                    'rescue': rescue,
                    'disk_prefix': self._disk_prefix,
                    'driver_type': driver_type,
                    'root_device_type': root_device_type,
                    'vif_type': FLAGS.libvirt_vif_type,
                    'nics': nics,
                    'ebs_root': ebs_root,
                    'ephemeral_device': ephemeral_device,
                    'volumes': volumes,
                    'use_virtio_for_bridges':
                            FLAGS.libvirt_use_virtio_for_bridges,
                    'ephemerals': ephemerals}

        root_device_name = driver.block_device_info_get_root(block_device_info)
        if root_device_name:
            xml_info['root_device'] = block_device.strip_dev(root_device_name)
            xml_info['root_device_name'] = root_device_name
        else:
            # NOTE(yamahata):
            # for nova.api.ec2.cloud.CloudController.get_metadata()
            xml_info['root_device'] = self.default_root_device
            db.instance_update(
                nova_context.get_admin_context(), instance['id'],
                {'root_device_name': '/dev/' + self.default_root_device})

        if ephemeral_device:
            swap_device = self.default_third_device
            db.instance_update(
                nova_context.get_admin_context(), instance['id'],
                {'default_ephemeral_device':
                 '/dev/' + self.default_second_device})
        else:
            swap_device = self.default_second_device

        swap = driver.block_device_info_get_swap(block_device_info)
        if driver.swap_is_usable(swap):
            xml_info['swap_device'] = block_device.strip_dev(
                swap['device_name'])
        elif (inst_type['swap'] > 0 and
              not self._volume_in_mapping(swap_device,
                                          block_device_info)):
            xml_info['swap_device'] = swap_device
            db.instance_update(
                nova_context.get_admin_context(), instance['id'],
                {'default_swap_device': '/dev/' + swap_device})

        config_drive = False
        if instance.get('config_drive') or instance.get('config_drive_id'):
            xml_info['config_drive'] = xml_info['basepath'] + "/disk.config"

        if FLAGS.vnc_enabled and FLAGS.libvirt_type not in ('lxc', 'uml'):
            xml_info['vncserver_listen'] = FLAGS.vncserver_listen
            xml_info['vnc_keymap'] = FLAGS.vnc_keymap
        if not rescue:
            if instance['kernel_id']:
                xml_info['kernel'] = xml_info['basepath'] + "/kernel"

            if instance['ramdisk_id']:
                xml_info['ramdisk'] = xml_info['basepath'] + "/ramdisk"

            xml_info['disk'] = xml_info['basepath'] + "/disk"
        return xml_info

    def to_xml(self, instance, network_info, image_meta=None, rescue=False,
               block_device_info=None):
        # TODO(termie): cache?
        LOG.debug(_('Starting toXML method'), instance=instance)
        xml_info = self._prepare_xml_info(instance, network_info, image_meta,
                                          rescue, block_device_info)
        xml = str(Template(self.libvirt_xml, searchList=[xml_info]))
        LOG.debug(_('Finished toXML method'), instance=instance)
        return xml

    def _lookup_by_name(self, instance_name):
        """Retrieve libvirt domain object given an instance name.

        All libvirt error handling should be handled in this method and
        relevant nova exceptions should be raised in response.

        """
        try:
            return self._conn.lookupByName(instance_name)
        except libvirt.libvirtError as ex:
            error_code = ex.get_error_code()
            if error_code == libvirt.VIR_ERR_NO_DOMAIN:
                raise exception.InstanceNotFound(instance_id=instance_name)

            msg = _("Error from libvirt while looking up %(instance_name)s: "
                    "[Error Code %(error_code)s] %(ex)s") % locals()
            raise exception.Error(msg)

    def get_info(self, instance_name):
        """Retrieve information from libvirt for a specific instance name.

        If a libvirt error is encountered during lookup, we might raise a
        NotFound exception or Error exception depending on how severe the
        libvirt error is.

        """
        virt_dom = self._lookup_by_name(instance_name)
        (state, max_mem, mem, num_cpu, cpu_time) = virt_dom.info()
        return {'state': state,
                'max_mem': max_mem,
                'mem': mem,
                'num_cpu': num_cpu,
                'cpu_time': cpu_time}

    def _create_new_domain(self, xml, persistent=True, launch_flags=0):
        # NOTE(justinsb): libvirt has two types of domain:
        # * a transient domain disappears when the guest is shutdown
        # or the host is rebooted.
        # * a permanent domain is not automatically deleted
        # NOTE(justinsb): Even for ephemeral instances, transient seems risky

        if persistent:
            # To create a persistent domain, first define it, then launch it.
            domain = self._conn.defineXML(xml)

            domain.createWithFlags(launch_flags)
        else:
            # createXML call creates a transient domain
            domain = self._conn.createXML(xml, launch_flags)

        return domain

    def get_all_block_devices(self):
        """
        Return all block devices in use on this node.
        """
        devices = []
        for dom_id in self._conn.listDomainsID():
            domain = self._conn.lookupByID(dom_id)
            try:
                doc = ElementTree.fromstring(domain.XMLDesc(0))
            except Exception:
                continue
            ret = doc.findall('./devices/disk')
            for node in ret:
                if node.get('type') != 'block':
                    continue
                for child in node.getchildren():
                    if child.tag == 'source':
                        devices.append(child.get('dev'))
        return devices

    def get_disks(self, instance_name):
        """
        Note that this function takes an instance name.

        Returns a list of all block devices for this domain.
        """
        domain = self._lookup_by_name(instance_name)
        xml = domain.XMLDesc(0)
        doc = None

        try:
            doc = ElementTree.fromstring(xml)
        except Exception:
            return []

        disks = []

        ret = doc.findall('./devices/disk')

        for node in ret:
            devdst = None

            for child in node.children:
                if child.name == 'target':
                    devdst = child.prop('dev')

            if devdst is None:
                continue

            disks.append(devdst)

        return disks

    def get_interfaces(self, instance_name):
        """
        Note that this function takes an instance name.

        Returns a list of all network interfaces for this instance.
        """
        domain = self._lookup_by_name(instance_name)
        xml = domain.XMLDesc(0)
        doc = None

        try:
            doc = ElementTree.fromstring(xml)
        except Exception:
            return []

        interfaces = []

        ret = doc.findall('./devices/interface')

        for node in ret:
            devdst = None

            for child in list(node):
                if child.tag == 'target':
                    devdst = child.attrib['dev']

            if devdst is None:
                continue

            interfaces.append(devdst)

        return interfaces

    @staticmethod
    def get_vcpu_total():
        """Get vcpu number of physical computer.

        :returns: the number of cpu core.

        """

        # On certain platforms, this will raise a NotImplementedError.
        try:
            return multiprocessing.cpu_count()
        except NotImplementedError:
            LOG.warn(_("Cannot get the number of cpu, because this "
                       "function is not implemented for this platform. "
                       "This error can be safely ignored for now."))
            return 0

    @staticmethod
    def get_memory_mb_total():
        """Get the total memory size(MB) of physical computer.

        :returns: the total amount of memory(MB).

        """

        if sys.platform.upper() not in ['LINUX2', 'LINUX3']:
            return 0

        meminfo = open('/proc/meminfo').read().split()
        idx = meminfo.index('MemTotal:')
        # transforming kb to mb.
        return int(meminfo[idx + 1]) / 1024

    @staticmethod
    def get_local_gb_total():
        """Get the total hdd size(GB) of physical computer.

        :returns:
            The total amount of HDD(GB).
            Note that this value shows a partition where
            NOVA-INST-DIR/instances mounts.

        """

        stats = libvirt_utils.get_fs_info(FLAGS.instances_path)
        return stats['total'] / (1024 ** 3)

    def get_vcpu_used(self):
        """ Get vcpu usage number of physical computer.

        :returns: The total number of vcpu that currently used.

        """

        total = 0
        for dom_id in self._conn.listDomainsID():
            dom = self._conn.lookupByID(dom_id)
            vcpus = dom.vcpus()
            if vcpus is None:
                # dom.vcpus is not implemented for lxc, but returning 0 for
                # a used count is hardly useful for something measuring usage
                total += 1
            else:
                total += len(vcpus[1])
        return total

    def get_memory_mb_used(self):
        """Get the free memory size(MB) of physical computer.

        :returns: the total usage of memory(MB).

        """

        if sys.platform.upper() not in ['LINUX2', 'LINUX3']:
            return 0

        m = open('/proc/meminfo').read().split()
        idx1 = m.index('MemFree:')
        idx2 = m.index('Buffers:')
        idx3 = m.index('Cached:')
        avail = (int(m[idx1 + 1]) + int(m[idx2 + 1]) + int(m[idx3 + 1])) / 1024
        return  self.get_memory_mb_total() - avail

    def get_local_gb_used(self):
        """Get the free hdd size(GB) of physical computer.

        :returns:
           The total usage of HDD(GB).
           Note that this value shows a partition where
           NOVA-INST-DIR/instances mounts.

        """

        stats = libvirt_utils.get_fs_info(FLAGS.instances_path)
        return stats['used'] / (1024 ** 3)

    def get_hypervisor_type(self):
        """Get hypervisor type.

        :returns: hypervisor type (ex. qemu)

        """

        return self._conn.getType()

    def get_hypervisor_version(self):
        """Get hypervisor version.

        :returns: hypervisor version (ex. 12003)

        """

        # NOTE(justinsb): getVersion moved between libvirt versions
        # Trying to do be compatible with older versions is a lost cause
        # But ... we can at least give the user a nice message
        method = getattr(self._conn, 'getVersion', None)
        if method is None:
            raise exception.Error(_("libvirt version is too old"
                                    " (does not support getVersion)"))
            # NOTE(justinsb): If we wanted to get the version, we could:
            # method = getattr(libvirt, 'getVersion', None)
            # NOTE(justinsb): This would then rely on a proper version check

        return method()

    def get_cpu_info(self):
        """Get cpuinfo information.

        Obtains cpu feature from virConnect.getCapabilities,
        and returns as a json string.

        :return: see above description

        """

        xml = self._conn.getCapabilities()
        xml = ElementTree.fromstring(xml)
        nodes = xml.findall('.//host/cpu')
        if len(nodes) != 1:
            reason = _("'<cpu>' must be 1, but %d\n") % len(nodes)
            reason += xml.serialize()
            raise exception.InvalidCPUInfo(reason=reason)

        cpu_info = dict()

        arch_nodes = xml.findall('.//host/cpu/arch')
        if arch_nodes:
            cpu_info['arch'] = arch_nodes[0].text

        model_nodes = xml.findall('.//host/cpu/model')
        if model_nodes:
            cpu_info['model'] = model_nodes[0].text

        vendor_nodes = xml.findall('.//host/cpu/vendor')
        if vendor_nodes:
            cpu_info['vendor'] = vendor_nodes[0].text

        topology_nodes = xml.findall('.//host/cpu/topology')
        topology = dict()
        if topology_nodes:
            topology_node = topology_nodes[0]

            keys = ['cores', 'sockets', 'threads']
            tkeys = topology_node.keys()
            if set(tkeys) != set(keys):
                ks = ', '.join(keys)
                reason = _("topology (%(topology)s) must have %(ks)s")
                raise exception.InvalidCPUInfo(reason=reason % locals())
            for key in keys:
                topology[key] = topology_node.get(key)

        feature_nodes = xml.findall('.//host/cpu/feature')
        features = list()
        for nodes in feature_nodes:
            features.append(nodes.get('name'))

        cpu_info['topology'] = topology
        cpu_info['features'] = features
        return utils.dumps(cpu_info)

    def block_stats(self, instance_name, disk):
        """
        Note that this function takes an instance name.
        """
        domain = self._lookup_by_name(instance_name)
        return domain.blockStats(disk)

    def interface_stats(self, instance_name, interface):
        """
        Note that this function takes an instance name.
        """
        domain = self._lookup_by_name(instance_name)
        return domain.interfaceStats(interface)

    def get_console_pool_info(self, console_type):
        #TODO(mdragon): console proxy should be implemented for libvirt,
        #               in case someone wants to use it with kvm or
        #               such. For now return fake data.
        return  {'address': '127.0.0.1',
                 'username': 'fakeuser',
                 'password': 'fakepassword'}

    def refresh_security_group_rules(self, security_group_id):
        self.firewall_driver.refresh_security_group_rules(security_group_id)

    def refresh_security_group_members(self, security_group_id):
        self.firewall_driver.refresh_security_group_members(security_group_id)

    def refresh_provider_fw_rules(self):
        self.firewall_driver.refresh_provider_fw_rules()

    def update_available_resource(self, ctxt, host):
        """Updates compute manager resource info on ComputeNode table.

        This method is called as an periodic tasks and is used only
        in live migration currently.

        :param ctxt: security context
        :param host: hostname that compute manager is currently running

        """

        try:
            service_ref = db.service_get_all_compute_by_host(ctxt, host)[0]
        except exception.NotFound:
            raise exception.ComputeServiceUnavailable(host=host)

        # Updating host information
        dic = {'vcpus': self.get_vcpu_total(),
               'memory_mb': self.get_memory_mb_total(),
               'local_gb': self.get_local_gb_total(),
               'vcpus_used': self.get_vcpu_used(),
               'memory_mb_used': self.get_memory_mb_used(),
               'local_gb_used': self.get_local_gb_used(),
               'hypervisor_type': self.get_hypervisor_type(),
               'hypervisor_version': self.get_hypervisor_version(),
               'cpu_info': self.get_cpu_info(),
               'service_id': service_ref['id'],
               'disk_available_least': self.get_disk_available_least()}

        compute_node_ref = service_ref['compute_node']
        if not compute_node_ref:
            LOG.info(_('Compute_service record created for %s ') % host)
            db.compute_node_create(ctxt, dic)
        else:
            LOG.info(_('Compute_service record updated for %s ') % host)
            db.compute_node_update(ctxt, compute_node_ref[0]['id'], dic)

    def compare_cpu(self, cpu_info):
        """Checks the host cpu is compatible to a cpu given by xml.

        "xml" must be a part of libvirt.openReadonly().getCapabilities().
        return values follows by virCPUCompareResult.
        if 0 > return value, do live migration.
        'http://libvirt.org/html/libvirt-libvirt.html#virCPUCompareResult'

        :param cpu_info: json string that shows cpu feature(see get_cpu_info())
        :returns:
            None. if given cpu info is not compatible to this server,
            raise exception.

        """

        LOG.info(_('Instance launched has CPU info:\n%s') % cpu_info)
        dic = utils.loads(cpu_info)
        xml = str(Template(self.cpuinfo_xml, searchList=dic))
        LOG.info(_('to xml...\n:%s ' % xml))

        u = "http://libvirt.org/html/libvirt-libvirt.html#virCPUCompareResult"
        m = _("CPU doesn't have compatibility.\n\n%(ret)s\n\nRefer to %(u)s")
        # unknown character exists in xml, then libvirt complains
        try:
            ret = self._conn.compareCPU(xml, 0)
        except libvirt.libvirtError, e:
            ret = e.message
            LOG.error(m % locals())
            raise

        if ret <= 0:
            raise exception.InvalidCPUInfo(reason=m % locals())

        return

    def ensure_filtering_rules_for_instance(self, instance_ref, network_info,
                                            time=None):
        """Setting up filtering rules and waiting for its completion.

        To migrate an instance, filtering rules to hypervisors
        and firewalls are inevitable on destination host.
        ( Waiting only for filterling rules to hypervisor,
        since filtering rules to firewall rules can be set faster).

        Concretely, the below method must be called.
        - setup_basic_filtering (for nova-basic, etc.)
        - prepare_instance_filter(for nova-instance-instance-xxx, etc.)

        to_xml may have to be called since it defines PROJNET, PROJMASK.
        but libvirt migrates those value through migrateToURI(),
        so , no need to be called.

        Don't use thread for this method since migration should
        not be started when setting-up filtering rules operations
        are not completed.

        :params instance_ref: nova.db.sqlalchemy.models.Instance object

        """

        if not time:
            time = greenthread

        # If any instances never launch at destination host,
        # basic-filtering must be set here.
        self.firewall_driver.setup_basic_filtering(instance_ref, network_info)
        # setting up nova-instance-instance-xx mainly.
        self.firewall_driver.prepare_instance_filter(instance_ref,
                network_info)

        # wait for completion
        timeout_count = range(FLAGS.live_migration_retry_count)
        while timeout_count:
            if self.firewall_driver.instance_filter_exists(instance_ref,
                                                           network_info):
                break
            timeout_count.pop()
            if len(timeout_count) == 0:
                msg = _('Timeout migrating for %s. nwfilter not found.')
                raise exception.Error(msg % instance_ref.name)
            time.sleep(1)

    def live_migration(self, ctxt, instance_ref, dest,
                       post_method, recover_method, block_migration=False):
        """Spawning live_migration operation for distributing high-load.

        :params ctxt: security context
        :params instance_ref:
            nova.db.sqlalchemy.models.Instance object
            instance object that is migrated.
        :params dest: destination host
        :params block_migration: destination host
        :params post_method:
            post operation method.
            expected nova.compute.manager.post_live_migration.
        :params recover_method:
            recovery method when any exception occurs.
            expected nova.compute.manager.recover_live_migration.
        :params block_migration: if true, do block migration.

        """

        greenthread.spawn(self._live_migration, ctxt, instance_ref, dest,
                          post_method, recover_method, block_migration)

    def _live_migration(self, ctxt, instance_ref, dest, post_method,
                        recover_method, block_migration=False):
        """Do live migration.

        :params ctxt: security context
        :params instance_ref:
            nova.db.sqlalchemy.models.Instance object
            instance object that is migrated.
        :params dest: destination host
        :params post_method:
            post operation method.
            expected nova.compute.manager.post_live_migration.
        :params recover_method:
            recovery method when any exception occurs.
            expected nova.compute.manager.recover_live_migration.

        """

        # Do live migration.
        try:
            if block_migration:
                flaglist = FLAGS.block_migration_flag.split(',')
            else:
                flaglist = FLAGS.live_migration_flag.split(',')
            flagvals = [getattr(libvirt, x.strip()) for x in flaglist]
            logical_sum = reduce(lambda x, y: x | y, flagvals)

            dom = self._conn.lookupByName(instance_ref.name)
            dom.migrateToURI(FLAGS.live_migration_uri % dest,
                             logical_sum,
                             None,
                             FLAGS.live_migration_bandwidth)

        except Exception:
            with utils.save_and_reraise_exception():
                recover_method(ctxt, instance_ref, dest, block_migration)

        # Waiting for completion of live_migration.
        timer = utils.LoopingCall(f=None)

        def wait_for_live_migration():
            """waiting for live migration completion"""
            try:
                self.get_info(instance_ref.name)['state']
            except exception.NotFound:
                timer.stop()
                post_method(ctxt, instance_ref, dest, block_migration)

        timer.f = wait_for_live_migration
        timer.start(interval=0.5, now=True)

    def pre_live_migration(self, block_device_info):
        """Preparation live migration.

        :params block_device_info:
            It must be the result of _get_instance_volume_bdms()
            at compute manager.
        """

        # Establishing connection to volume server.
        block_device_mapping = driver.block_device_info_get_mapping(
            block_device_info)
        for vol in block_device_mapping:
            connection_info = vol['connection_info']
            mountpoint = vol['mount_device']
            xml = self.volume_driver_method('connect_volume',
                                            connection_info,
                                            mountpoint)

    def pre_block_migration(self, ctxt, instance_ref, disk_info_json):
        """Preparation block migration.

        :params ctxt: security context
        :params instance_ref:
            nova.db.sqlalchemy.models.Instance object
            instance object that is migrated.
        :params disk_info_json:
            json strings specified in get_instance_disk_info

        """
        disk_info = utils.loads(disk_info_json)

        # make instance directory
        instance_dir = os.path.join(FLAGS.instances_path, instance_ref['name'])
        if os.path.exists(instance_dir):
            raise exception.DestinationDiskExists(path=instance_dir)
        os.mkdir(instance_dir)

        for info in disk_info:
            base = os.path.basename(info['path'])
            # Get image type and create empty disk image, and
            # create backing file in case of qcow2.
            instance_disk = os.path.join(instance_dir, base)
            if not info['backing_file']:
                libvirt_utils.create_image(info['type'], instance_disk,
                                           info['disk_size'])
            else:
                # Creating backing file follows same way as spawning instances.
                cache_name = os.path.basename(info['backing_file'])
                # Remove any size tags which the cache manages
                cache_name = cache_name.split('_')[0]

                self._cache_image(fn=libvirt_utils.fetch_image,
                    context=ctxt,
                    target=instance_disk,
                    fname=cache_name,
                    cow=FLAGS.use_cow_images,
                    image_id=instance_ref['image_ref'],
                    user_id=instance_ref['user_id'],
                    project_id=instance_ref['project_id'],
                    size=info['disk_size'])

        # if image has kernel and ramdisk, just download
        # following normal way.
        if instance_ref['kernel_id']:
            libvirt_utils.fetch_image(nova_context.get_admin_context(),
                              os.path.join(instance_dir, 'kernel'),
                              instance_ref['kernel_id'],
                              instance_ref['user_id'],
                              instance_ref['project_id'])
            if instance_ref['ramdisk_id']:
                libvirt_utils.fetch_image(nova_context.get_admin_context(),
                                  os.path.join(instance_dir, 'ramdisk'),
                                  instance_ref['ramdisk_id'],
                                  instance_ref['user_id'],
                                  instance_ref['project_id'])

    def post_live_migration_at_destination(self, ctxt,
                                           instance_ref,
                                           network_info,
                                           block_migration):
        """Post operation of live migration at destination host.

        :params ctxt: security context
        :params instance_ref:
            nova.db.sqlalchemy.models.Instance object
            instance object that is migrated.
        :params network_info: instance network infomation
        :params : block_migration: if true, post operation of block_migraiton.
        """
        # Define migrated instance, otherwise, suspend/destroy does not work.
        dom_list = self._conn.listDefinedDomains()
        if instance_ref.name not in dom_list:
            instance_dir = os.path.join(FLAGS.instances_path,
                                        instance_ref.name)
            xml_path = os.path.join(instance_dir, 'libvirt.xml')
            # In case of block migration, destination does not have
            # libvirt.xml
            if not os.path.isfile(xml_path):
                xml = self.to_xml(instance_ref, network_info=network_info)
                f = open(os.path.join(instance_dir, 'libvirt.xml'), 'w+')
                f.write(xml)
                f.close()
            # libvirt.xml should be made by to_xml(), but libvirt
            # does not accept to_xml() result, since uuid is not
            # included in to_xml() result.
            dom = self._lookup_by_name(instance_ref.name)
            self._conn.defineXML(dom.XMLDesc(0))

    def get_instance_disk_info(self, instance_name):
        """Preparation block migration.

        :params ctxt: security context
        :params instance_ref:
            nova.db.sqlalchemy.models.Instance object
            instance object that is migrated.
        :return:
            json strings with below format.
           "[{'path':'disk', 'type':'raw',
              'virt_disk_size':'10737418240',
              'backing_file':'backing_file',
              'disk_size':'83886080'},...]"

        """
        disk_info = []

        virt_dom = self._lookup_by_name(instance_name)
        xml = virt_dom.XMLDesc(0)
        doc = ElementTree.fromstring(xml)
        disk_nodes = doc.findall('.//devices/disk')
        path_nodes = doc.findall('.//devices/disk/source')
        driver_nodes = doc.findall('.//devices/disk/driver')

        for cnt, path_node in enumerate(path_nodes):
            disk_type = disk_nodes[cnt].get('type')
            path = path_node.get('file')

            if disk_type != 'file':
                LOG.debug(_('skipping %(path)s since it looks like volume') %
                          locals())
                continue

            disk_type = driver_nodes[cnt].get('type')
            if disk_type == "qcow2":
                out, err = utils.execute('qemu-img', 'info', path)

                # virtual size:
                size = [i.split('(')[1].split()[0] for i in out.split('\n')
                    if i.strip().find('virtual size') >= 0]
                virt_size = int(size[0])

                # real disk size:
                dk_size = int(os.path.getsize(path))

                # backing file:(actual path:)
                backing_file = libvirt_utils.get_disk_backing_file(path)
            else:
                dk_size = int(os.path.getsize(path))
                backing_file = ""
                virt_size = 0

            disk_info.append({'type': disk_type,
                              'path': path,
                              'virt_disk_size': virt_size,
                              'backing_file': backing_file,
                              'disk_size': dk_size})
        return utils.dumps(disk_info)

    def get_disk_available_least(self):
        """Return disk available least size.

        The size of available disk, when block_migration command given
        disk_over_commit param is FALSE.

        The size that deducted real nstance disk size from the total size
        of the virtual disk of all instances.

        """
        # available size of the disk
        dk_sz_gb = self.get_local_gb_total() - self.get_local_gb_used()

        # Disk size that all instance uses : virtual_size - disk_size
        instances_name = self.list_instances()
        instances_sz = 0
        for i_name in instances_name:
            disk_infos = utils.loads(self.get_instance_disk_info(i_name))
            for info in disk_infos:
                i_vt_sz = int(info['virt_disk_size'])
                i_dk_sz = int(info['disk_size'])
                instances_sz += i_vt_sz - i_dk_sz

        # Disk available least size
        available_least_size = dk_sz_gb * (1024 ** 3) - instances_sz
        return (available_least_size / 1024 / 1024 / 1024)

    def unfilter_instance(self, instance_ref, network_info):
        """See comments of same method in firewall_driver."""
        self.firewall_driver.unfilter_instance(instance_ref,
                                               network_info=network_info)

    def update_host_status(self):
        """Retrieve status info from libvirt.

        Query libvirt to get the state of the compute node, such
        as memory and disk usage.
        """
        return self.host_state.update_status()

    def get_host_stats(self, refresh=False):
        """Return the current state of the host.

        If 'refresh' is True, run update the stats first."""
        return self.host_state.get_host_stats(refresh=refresh)

    def host_power_action(self, host, action):
        """Reboots, shuts down or powers up the host."""
        raise NotImplementedError()

    def set_host_enabled(self, host, enabled):
        """Sets the specified host's ability to accept new instances."""
        pass

    def manage_image_cache(self, context):
        """Manage the local cache of images."""
        self.image_cache_manager.verify_base_images(context)

    @exception.wrap_exception()
    def migrate_disk_and_power_off(self, context, instance, dest,
                                   instance_type, network_info):
        LOG.debug(_("Instance %s: Starting migrate_disk_and_power_off"),
                   instance['name'])
        disk_info_text = self.get_instance_disk_info(instance['name'])
        disk_info = utils.loads(disk_info_text)

        self._destroy(instance, network_info, cleanup=False)

        # copy disks to destination
        # if disk type is qcow2, convert to raw then send to dest.
        # rename instance dir to +_resize at first for using
        # shared storage for instance dir (eg. NFS).
        same_host = (dest == self.get_host_ip_addr())
        inst_base = "%s/%s" % (FLAGS.instances_path, instance['name'])
        inst_base_resize = inst_base + "_resize"
        try:
            utils.execute('mv', inst_base, inst_base_resize)
            if same_host:
                utils.execute('mkdir', '-p', inst_base)
            else:
                utils.execute('ssh', dest, 'mkdir', '-p', inst_base)
            for info in disk_info:
                # assume inst_base == dirname(info['path'])
                to_path = "%s:%s" % (dest, info['path'])
                fname = os.path.basename(info['path'])
                from_path = os.path.join(inst_base_resize, fname)
                if info['type'] == 'qcow2':
                    tmp_path = from_path + "_rbase"
                    utils.execute('qemu-img', 'convert', '-f', 'qcow2',
                                  '-O', 'raw', from_path, tmp_path)
                    if same_host:
                        utils.execute('mv', tmp_path, info['path'])
                    else:
                        utils.execute('scp', tmp_path, to_path)
                        utils.execute('rm', '-f', tmp_path)
                else:  # raw
                    if same_host:
                        utils.execute('cp', from_path, info['path'])
                    else:
                        utils.execute('scp', from_path, to_path)
        except Exception, e:
            try:
                if os.path.exists(inst_base_resize):
                    utils.execute('rm', '-rf', inst_base)
                    utils.execute('mv', inst_base_resize, inst_base)
                    utils.execute('ssh', dest, 'rm', '-rf', inst_base)
            except:
                pass
            raise e

        return disk_info_text

    def _wait_for_running(self, instance_name):
        try:
            state = self.get_info(instance_name)['state']
        except exception.NotFound:
            msg = _("During wait running, %s disappeared.") % instance_name
            LOG.error(msg)
            raise utils.LoopingCallDone

        if state == power_state.RUNNING:
            msg = _("Instance %s running successfully.") % instance_name
            LOG.info(msg)
            raise utils.LoopingCallDone

    @exception.wrap_exception()
    def finish_migration(self, context, migration, instance, disk_info,
                         network_info, image_meta, resize_instance):
        LOG.debug(_("Instance %s: Starting finish_migration"),
                   instance['name'])

        # resize disks. only "disk" and "disk.local" are necessary.
        disk_info = utils.loads(disk_info)
        for info in disk_info:
            fname = os.path.basename(info['path'])
            if fname == 'disk':
                disk.extend(info['path'],
                            instance['root_gb'] * 1024 * 1024 * 1024)
            elif fname == 'disk.local':
                disk.extend(info['path'],
                            instance['ephemeral_gb'] * 1024 * 1024 * 1024)
            if FLAGS.use_cow_images:
                # back to qcow2 (no backing_file though) so that snapshot
                # will be available
                path_qcow = info['path'] + '_qcow'
                utils.execute('qemu-img', 'convert', '-f', 'raw',
                              '-O', 'qcow2', info['path'], path_qcow)
                utils.execute('mv', path_qcow, info['path'])

        xml = self.to_xml(instance, network_info)

        self.plug_vifs(instance, network_info)
        self.firewall_driver.setup_basic_filtering(instance, network_info)
        self.firewall_driver.prepare_instance_filter(instance, network_info)
        # assume _create_image do nothing if a target file exists.
        # TODO(oda): injecting files is not necessary
        self._create_image(context, instance, xml,
                                    network_info=network_info,
                                    block_device_info=None)

        domain = self._create_new_domain(xml)

        self.firewall_driver.apply_instance_filter(instance, network_info)

        timer = utils.LoopingCall(self._wait_for_running, instance['name'])
        return timer.start(interval=0.5, now=True)

    @exception.wrap_exception()
    def finish_revert_migration(self, instance, network_info):
        LOG.debug(_("Instance %s: Starting finish_revert_migration"),
                   instance['name'])

        inst_base = "%s/%s" % (FLAGS.instances_path, instance['name'])
        inst_base_resize = inst_base + "_resize"
        utils.execute('mv', inst_base_resize, inst_base)

        xml_path = os.path.join(inst_base, 'libvirt.xml')
        xml = open(xml_path).read()

        self.plug_vifs(instance, network_info)
        self.firewall_driver.setup_basic_filtering(instance, network_info)
        self.firewall_driver.prepare_instance_filter(instance, network_info)
        # images already exist
        domain = self._create_new_domain(xml)
        self.firewall_driver.apply_instance_filter(instance, network_info)

        timer = utils.LoopingCall(self._wait_for_running, instance['name'])
        return timer.start(interval=0.5, now=True)

    def confirm_migration(self, migration, instance, network_info):
        """Confirms a resize, destroying the source VM"""
        self._cleanup_resize(instance)


class HostState(object):
    """Manages information about the compute node through libvirt"""
    def __init__(self, read_only):
        super(HostState, self).__init__()
        self.read_only = read_only
        self._stats = {}
        self.connection = None
        self.update_status()

    def get_host_stats(self, refresh=False):
        """Return the current state of the host.

        If 'refresh' is True, run update the stats first."""
        if refresh:
            self.update_status()
        return self._stats

    def update_status(self):
        """Retrieve status info from libvirt."""
        LOG.debug(_("Updating host stats"))
        if self.connection is None:
            self.connection = get_connection(self.read_only)
        data = {}
        data["vcpus"] = self.connection.get_vcpu_total()
        data["vcpus_used"] = self.connection.get_vcpu_used()
        data["cpu_info"] = utils.loads(self.connection.get_cpu_info())
        data["disk_total"] = self.connection.get_local_gb_total()
        data["disk_used"] = self.connection.get_local_gb_used()
        data["disk_available"] = data["disk_total"] - data["disk_used"]
        data["host_memory_total"] = self.connection.get_memory_mb_total()
        data["host_memory_free"] = (data["host_memory_total"] -
                                    self.connection.get_memory_mb_used())
        data["hypervisor_type"] = self.connection.get_hypervisor_type()
        data["hypervisor_version"] = self.connection.get_hypervisor_version()

        self._stats = data

        return data
