# Copyright (c) 2012 OpenStack Foundation
# 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.

"""
Track resources like memory and disk for a compute host.  Provides the
scheduler with useful information about availability through the ComputeNode
model.
"""
import copy

from oslo_config import cfg
from oslo_log import log as logging
from oslo_serialization import jsonutils
from oslo_utils import importutils

from nova.compute import claims
from nova.compute import flavors
from nova.compute import monitors
from nova.compute import resources as ext_resources
from nova.compute import task_states
from nova.compute import vm_states
from nova import conductor
from nova import exception
from nova.i18n import _, _LI, _LW
from nova import objects
from nova.objects import base as obj_base
from nova.objects import instance as instance_obj
from nova.pci import manager as pci_manager
from nova.pci import whitelist as pci_whitelist
from nova import rpc
from nova.scheduler import client as scheduler_client
from nova import utils
from nova.virt import hardware

resource_tracker_opts = [
    cfg.IntOpt('reserved_host_disk_mb', default=0,
               help='Amount of disk in MB to reserve for the host'),
    cfg.IntOpt('reserved_host_memory_mb', default=512,
               help='Amount of memory in MB to reserve for the host'),
    cfg.StrOpt('compute_stats_class',
               default='nova.compute.stats.Stats',
               help='Class that will manage stats for the local compute host'),
    cfg.ListOpt('compute_resources',
                default=['vcpu'],
                help='The names of the extra resources to track.'),
]

CONF = cfg.CONF
CONF.register_opts(resource_tracker_opts)

LOG = logging.getLogger(__name__)
COMPUTE_RESOURCE_SEMAPHORE = "compute_resources"

CONF.import_opt('my_ip', 'nova.netconf')


class ResourceTracker(object):
    """Compute helper class for keeping track of resource usage as instances
    are built and destroyed.
    """

    def __init__(self, host, driver, nodename):
        self.host = host
        self.driver = driver
        self.pci_tracker = None
        self.pci_filter = pci_whitelist.get_pci_devices_filter()
        self.nodename = nodename
        self.compute_node = None
        self.stats = importutils.import_object(CONF.compute_stats_class)
        self.tracked_instances = {}
        self.tracked_migrations = {}
        self.conductor_api = conductor.API()
        monitor_handler = monitors.ResourceMonitorHandler()
        self.monitors = monitor_handler.choose_monitors(self)
        self.ext_resources_handler = \
            ext_resources.ResourceHandler(CONF.compute_resources)
        self.old_resources = {}
        self.scheduler_client = scheduler_client.SchedulerClient()

    @utils.synchronized(COMPUTE_RESOURCE_SEMAPHORE)
    def instance_claim(self, context, instance_ref, limits=None):
        """Indicate that some resources are needed for an upcoming compute
        instance build operation.

        This should be called before the compute node is about to perform
        an instance build operation that will consume additional resources.

        :param context: security context
        :param instance_ref: instance to reserve resources for
        :param limits: Dict of oversubscription limits for memory, disk,
                       and CPUs.
        :returns: A Claim ticket representing the reserved resources.  It can
                  be used to revert the resource usage if an error occurs
                  during the instance build.
        """
        if self.disabled:
            # compute_driver doesn't support resource tracking, just
            # set the 'host' and node fields and continue the build:
            self._set_instance_host_and_node(context, instance_ref)
            return claims.NopClaim()

        # sanity checks:
        if instance_ref['host']:
            LOG.warning(_LW("Host field should not be set on the instance "
                            "until resources have been claimed."),
                        instance=instance_ref)

        if instance_ref['node']:
            LOG.warning(_LW("Node field should not be set on the instance "
                            "until resources have been claimed."),
                        instance=instance_ref)

        # get memory overhead required to build this instance:
        overhead = self.driver.estimate_instance_overhead(instance_ref)
        LOG.debug("Memory overhead for %(flavor)d MB instance; %(overhead)d "
                  "MB", {'flavor': instance_ref['memory_mb'],
                          'overhead': overhead['memory_mb']})

        claim = claims.Claim(context, instance_ref, self, self.compute_node,
                             overhead=overhead, limits=limits)

        # self._set_instance_host_and_node() will save instance_ref to the DB
        # so set instance_ref['numa_topology'] first.  We need to make sure
        # that numa_topology is saved while under COMPUTE_RESOURCE_SEMAPHORE
        # so that the resource audit knows about any cpus we've pinned.
        instance_ref['numa_topology'] = claim.claimed_numa_topology
        self._set_instance_host_and_node(context, instance_ref)

        # Mark resources in-use and update stats
        self._update_usage_from_instance(context, self.compute_node,
                                         instance_ref)

        elevated = context.elevated()
        # persist changes to the compute node:
        self._update(elevated, self.compute_node)

        return claim

    @utils.synchronized(COMPUTE_RESOURCE_SEMAPHORE)
    def resize_claim(self, context, instance, instance_type,
                     image_meta=None, limits=None):
        """Indicate that resources are needed for a resize operation to this
        compute host.
        :param context: security context
        :param instance: instance object to reserve resources for
        :param instance_type: new instance_type being resized to
        :param limits: Dict of oversubscription limits for memory, disk,
        and CPUs
        :returns: A Claim ticket representing the reserved resources.  This
        should be turned into finalize  a resource claim or free
        resources after the compute operation is finished.
        """
        image_meta = image_meta or {}

        if self.disabled:
            # compute_driver doesn't support resource tracking, just
            # generate the migration record and continue the resize:
            migration = self._create_migration(context, instance,
                                               instance_type)
            return claims.NopClaim(migration=migration)

        # get memory overhead required to build this instance:
        overhead = self.driver.estimate_instance_overhead(instance_type)
        LOG.debug("Memory overhead for %(flavor)d MB instance; %(overhead)d "
                  "MB", {'flavor': instance_type['memory_mb'],
                          'overhead': overhead['memory_mb']})

        instance_ref = instance_obj.compat_instance(instance)
        claim = claims.ResizeClaim(context, instance_ref, instance_type,
                                   image_meta, self, self.compute_node,
                                   overhead=overhead, limits=limits)

        migration = self._create_migration(context, instance_ref,
                                           instance_type)
        claim.migration = migration

        # Mark the resources in-use for the resize landing on this
        # compute host:
        self._update_usage_from_migration(context, instance_ref, image_meta,
                                              self.compute_node, migration)
        elevated = context.elevated()
        self._update(elevated, self.compute_node)

        return claim

    def _create_migration(self, context, instance, instance_type):
        """Create a migration record for the upcoming resize.  This should
        be done while the COMPUTE_RESOURCES_SEMAPHORE is held so the resource
        claim will not be lost if the audit process starts.
        """
        old_instance_type = flavors.extract_flavor(instance)
        migration = objects.Migration(context=context.elevated())
        migration.dest_compute = self.host
        migration.dest_node = self.nodename
        migration.dest_host = self.driver.get_host_ip_addr()
        migration.old_instance_type_id = old_instance_type['id']
        migration.new_instance_type_id = instance_type['id']
        migration.status = 'pre-migrating'
        migration.instance_uuid = instance['uuid']
        migration.source_compute = instance['host']
        migration.source_node = instance['node']
        migration.create()
        return migration

    def _set_instance_host_and_node(self, context, instance):
        """Tag the instance as belonging to this host.  This should be done
        while the COMPUTE_RESOURCES_SEMAPHORE is held so the resource claim
        will not be lost if the audit process starts.
        """
        instance.host = self.host
        instance.launched_on = self.host
        instance.node = self.nodename
        instance.save()

    @utils.synchronized(COMPUTE_RESOURCE_SEMAPHORE)
    def abort_instance_claim(self, context, instance):
        """Remove usage from the given instance."""
        # flag the instance as deleted to revert the resource usage
        # and associated stats:
        instance['vm_state'] = vm_states.DELETED
        self._update_usage_from_instance(context, self.compute_node, instance)

        self._update(context.elevated(), self.compute_node)

    @utils.synchronized(COMPUTE_RESOURCE_SEMAPHORE)
    def drop_resize_claim(self, context, instance, instance_type=None,
                          image_meta=None, prefix='new_'):
        """Remove usage for an incoming/outgoing migration."""
        if instance['uuid'] in self.tracked_migrations:
            migration, itype = self.tracked_migrations.pop(instance['uuid'])

            if not instance_type:
                ctxt = context.elevated()
                instance_type = self._get_instance_type(ctxt, instance, prefix)

            if image_meta is None:
                image_meta = utils.get_image_from_system_metadata(
                        instance['system_metadata'])

            if (instance_type is not None and
                instance_type['id'] == itype['id']):
                numa_topology = hardware.numa_get_constraints(
                    itype, image_meta)
                usage = self._get_usage_dict(
                        itype, numa_topology=numa_topology)
                if self.pci_tracker:
                    self.pci_tracker.update_pci_for_migration(context,
                                                              instance,
                                                              sign=-1)
                self._update_usage(context, self.compute_node, usage, sign=-1)

                ctxt = context.elevated()
                self._update(ctxt, self.compute_node)

    @utils.synchronized(COMPUTE_RESOURCE_SEMAPHORE)
    def update_usage(self, context, instance):
        """Update the resource usage and stats after a change in an
        instance
        """
        if self.disabled:
            return

        uuid = instance['uuid']

        # don't update usage for this instance unless it submitted a resource
        # claim first:
        if uuid in self.tracked_instances:
            self._update_usage_from_instance(context, self.compute_node,
                                             instance)
            self._update(context.elevated(), self.compute_node)

    @property
    def disabled(self):
        return self.compute_node is None

    def _init_compute_node(self, context, resources):
        """Initialise the compute node if it does not already exist.

        The resource tracker will be inoperable if compute_node
        is not defined. The compute_node will remain undefined if
        we fail to create it or if there is no associated service
        registered.

        If this method has to create a compute node it needs initial
        values - these come from resources.

        :param context: security context
        :param resources: initial values
        """

        # if there is already a compute node we don't
        # need to do anything
        if self.compute_node:
            return

        # TODO(pmurray): this lookup should be removed when the service_id
        # field in the compute node goes away. At the moment it is deprecated
        # but still a required field, so it has to be assigned below.
        service = self._get_service(context)
        if not service:
            # no service record, disable resource
            return

        # now try to get the compute node record from the
        # database. If we get one we are done.
        self.compute_node = self._get_compute_node(context)
        if self.compute_node:
            return

        # there was no local copy and none in the database
        # so we need to create a new compute node. This needs
        # to be initialised with resource values.
        cn = {}
        cn.update(resources)
        # TODO(pmurray) service_id is deprecated but is still a required field.
        # This should be removed when the field is changed.
        cn['service_id'] = service.id
        cn['host'] = self.host
        # initialize load stats from existing instances:
        self._write_ext_resources(cn)
        # NOTE(pmurray): the stats field is stored as a json string. The
        # json conversion will be done automatically by the ComputeNode object
        # so this can be removed when using ComputeNode.
        cn['stats'] = jsonutils.dumps(cn['stats'])
        # pci_passthrough_devices may be in resources but are not
        # stored in compute nodes
        cn.pop('pci_passthrough_devices', None)

        self.compute_node = self.conductor_api.compute_node_create(context, cn)
        LOG.info(_LI('Compute_service record created for '
                     '%(host)s:%(node)s'),
                 {'host': self.host, 'node': self.nodename})

    def _get_host_metrics(self, context, nodename):
        """Get the metrics from monitors and
        notify information to message bus.
        """
        metrics = []
        metrics_info = {}
        for monitor in self.monitors:
            try:
                metrics += monitor.get_metrics(nodename=nodename)
            except Exception:
                LOG.warning(_LW("Cannot get the metrics from %s."), monitor)
        if metrics:
            metrics_info['nodename'] = nodename
            metrics_info['metrics'] = metrics
            metrics_info['host'] = self.host
            metrics_info['host_ip'] = CONF.my_ip
            notifier = rpc.get_notifier(service='compute', host=nodename)
            notifier.info(context, 'compute.metrics.update', metrics_info)
        return metrics

    def update_available_resource(self, context):
        """Override in-memory calculations of compute node resource usage based
        on data audited from the hypervisor layer.

        Add in resource claims in progress to account for operations that have
        declared a need for resources, but not necessarily retrieved them from
        the hypervisor layer yet.
        """
        LOG.info(_LI("Auditing locally available compute resources for "
                     "node %(node)s"),
                 {'node': self.nodename})
        resources = self.driver.get_available_resource(self.nodename)

        if not resources:
            # The virt driver does not support this function
            LOG.info(_LI("Virt driver does not support "
                 "'get_available_resource'. Compute tracking is disabled."))
            self.compute_node = None
            return
        resources['host_ip'] = CONF.my_ip

        # We want the 'cpu_info' to be None from the POV of the
        # virt driver, but the DB requires it to be non-null so
        # just force it to empty string
        if ("cpu_info" not in resources or
            resources["cpu_info"] is None):
            resources["cpu_info"] = ''

        # TODO(berrange): remove this once all virt drivers are updated
        # to report topology
        if "numa_topology" not in resources:
            resources["numa_topology"] = None

        self._verify_resources(resources)

        self._report_hypervisor_resource_view(resources)

        self._update_available_resource(context, resources)

    @utils.synchronized(COMPUTE_RESOURCE_SEMAPHORE)
    def _update_available_resource(self, context, resources):

        # initialise the compute node object, creating it
        # if it does not already exist.
        self._init_compute_node(context, resources)

        # if we could not init the compute node the tracker will be
        # disabled and we should quit now
        if self.disabled:
            return

        if 'pci_passthrough_devices' in resources:
            devs = []
            for dev in jsonutils.loads(resources.pop(
                'pci_passthrough_devices')):
                if dev['dev_type'] == 'type-PF':
                    continue

                if self.pci_filter.device_assignable(dev):
                    devs.append(dev)

            if not self.pci_tracker:
                n_id = self.compute_node['id'] if self.compute_node else None
                self.pci_tracker = pci_manager.PciDevTracker(context,
                                                             node_id=n_id)
            self.pci_tracker.set_hvdevs(devs)

        # Grab all instances assigned to this node:
        instances = objects.InstanceList.get_by_host_and_node(
            context, self.host, self.nodename,
            expected_attrs=['system_metadata',
                            'numa_topology'])

        # Now calculate usage based on instance utilization:
        self._update_usage_from_instances(context, resources, instances)

        # Grab all in-progress migrations:
        migrations = objects.MigrationList.get_in_progress_by_host_and_node(
                context, self.host, self.nodename)

        self._update_usage_from_migrations(context, resources, migrations)

        # Detect and account for orphaned instances that may exist on the
        # hypervisor, but are not in the DB:
        orphans = self._find_orphaned_instances()
        self._update_usage_from_orphans(context, resources, orphans)

        # NOTE(yjiang5): Because pci device tracker status is not cleared in
        # this periodic task, and also because the resource tracker is not
        # notified when instances are deleted, we need remove all usages
        # from deleted instances.
        if self.pci_tracker:
            self.pci_tracker.clean_usage(instances, migrations, orphans)
            resources['pci_device_pools'] = self.pci_tracker.stats
        else:
            resources['pci_device_pools'] = []

        self._report_final_resource_view(resources)

        metrics = self._get_host_metrics(context, self.nodename)
        resources['metrics'] = jsonutils.dumps(metrics)

        # TODO(sbauza): Juno compute nodes are missing the host field and
        # the Juno ResourceTracker does not set this field, even if
        # the ComputeNode object can show it.
        # Unfortunately, as we're not yet using ComputeNode.save(), we need
        # to add this field in the resources dict until the RT is using
        # the ComputeNode.save() method for populating the table.
        # tl;dr: To be removed once RT is using ComputeNode.save()
        resources['host'] = self.host

        self._update(context, resources)
        LOG.info(_LI('Compute_service record updated for %(host)s:%(node)s'),
                     {'host': self.host, 'node': self.nodename})

    def _get_compute_node(self, context):
        """Returns compute node for the host and nodename."""
        try:
            compute = objects.ComputeNode.get_by_host_and_nodename(
                context, self.host, self.nodename)
            return obj_base.obj_to_primitive(compute)
        except exception.NotFound:
            LOG.warning(_LW("No compute node record for %(host)s:%(node)s"),
                        {'host': self.host, 'node': self.nodename})

    def _write_ext_resources(self, resources):
        resources['stats'] = {}
        resources['stats'].update(self.stats)
        self.ext_resources_handler.write_resources(resources)

    def _get_service(self, context):
        try:
            return objects.Service.get_by_compute_host(context, self.host)
        except exception.NotFound:
            LOG.warning(_LW("No service record for host %s"), self.host)

    def _report_hypervisor_resource_view(self, resources):
        """Log the hypervisor's view of free resources.

        This is just a snapshot of resource usage recorded by the
        virt driver.

        The following resources are logged:
            - free memory
            - free disk
            - free CPUs
            - assignable PCI devices
        """
        free_ram_mb = resources['memory_mb'] - resources['memory_mb_used']
        free_disk_gb = resources['local_gb'] - resources['local_gb_used']
        vcpus = resources['vcpus']
        if vcpus:
            free_vcpus = vcpus - resources['vcpus_used']
            LOG.debug("Hypervisor: free VCPUs: %s" % free_vcpus)
        else:
            free_vcpus = 'unknown'
            LOG.debug("Hypervisor: VCPU information unavailable")

        if ('pci_passthrough_devices' in resources and
                resources['pci_passthrough_devices']):
            LOG.debug("Hypervisor: assignable PCI devices: %s" %
                resources['pci_passthrough_devices'])

        pci_devices = resources.get('pci_passthrough_devices')

        LOG.debug("Hypervisor/Node resource view: "
                  "name=%(node)s "
                  "free_ram=%(free_ram)sMB "
                  "free_disk=%(free_disk)sGB "
                  "free_vcpus=%(free_vcpus)s "
                  "pci_devices=%(pci_devices)s",
                  {'node': self.nodename,
                   'free_ram': free_ram_mb,
                   'free_disk': free_disk_gb,
                   'free_vcpus': free_vcpus,
                   'pci_devices': pci_devices})

    def _report_final_resource_view(self, resources):
        """Report final calculate of physical memory, used virtual memory,
        disk, usable vCPUs, used virtual CPUs and PCI devices,
        including instance calculations and in-progress resource claims. These
        values will be exposed via the compute node table to the scheduler.
        """
        vcpus = resources['vcpus']
        if vcpus:
            tcpu = vcpus
            ucpu = resources['vcpus_used']
            LOG.info(_LI("Total usable vcpus: %(tcpu)s, "
                        "total allocated vcpus: %(ucpu)s"),
                        {'tcpu': vcpus, 'ucpu': resources['vcpus_used']})
        else:
            tcpu = 0
            ucpu = 0
        pci_device_pools = resources.get('pci_device_pools')
        LOG.info(_LI("Final resource view: "
                     "name=%(node)s "
                     "phys_ram=%(phys_ram)sMB "
                     "used_ram=%(used_ram)sMB "
                     "phys_disk=%(phys_disk)sGB "
                     "used_disk=%(used_disk)sGB "
                     "total_vcpus=%(total_vcpus)s "
                     "used_vcpus=%(used_vcpus)s "
                     "pci_stats=%(pci_stats)s"),
                 {'node': self.nodename,
                  'phys_ram': resources['memory_mb'],
                  'used_ram': resources['memory_mb_used'],
                  'phys_disk': resources['local_gb'],
                  'used_disk': resources['local_gb_used'],
                  'total_vcpus': tcpu,
                  'used_vcpus': ucpu,
                  'pci_stats': pci_device_pools})

    def _resource_change(self, resources):
        """Check to see if any resouces have changed."""
        if cmp(resources, self.old_resources) != 0:
            self.old_resources = copy.deepcopy(resources)
            return True
        return False

    def _update(self, context, values):
        """Update partial stats locally and populate them to Scheduler."""
        self._write_ext_resources(values)
        # NOTE(pmurray): the stats field is stored as a json string. The
        # json conversion will be done automatically by the ComputeNode object
        # so this can be removed when using ComputeNode.
        values['stats'] = jsonutils.dumps(values['stats'])

        if not self._resource_change(values):
            return
        if "service" in self.compute_node:
            del self.compute_node['service']
        # NOTE(sbauza): Now the DB update is asynchronous, we need to locally
        #               update the values
        self.compute_node.update(values)
        # Persist the stats to the Scheduler
        self._update_resource_stats(context, values)
        if self.pci_tracker:
            self.pci_tracker.save(context)

    def _update_resource_stats(self, context, values):
        stats = values.copy()
        stats['id'] = self.compute_node['id']
        self.scheduler_client.update_resource_stats(
            context, (self.host, self.nodename), stats)

    def _update_usage(self, context, resources, usage, sign=1):
        mem_usage = usage['memory_mb']

        overhead = self.driver.estimate_instance_overhead(usage)
        mem_usage += overhead['memory_mb']

        resources['memory_mb_used'] += sign * mem_usage
        resources['local_gb_used'] += sign * usage.get('root_gb', 0)
        resources['local_gb_used'] += sign * usage.get('ephemeral_gb', 0)

        # free ram and disk may be negative, depending on policy:
        resources['free_ram_mb'] = (resources['memory_mb'] -
                                    resources['memory_mb_used'])
        resources['free_disk_gb'] = (resources['local_gb'] -
                                     resources['local_gb_used'])

        resources['running_vms'] = self.stats.num_instances
        self.ext_resources_handler.update_from_instance(usage, sign)

        # Calculate the numa usage
        free = sign == -1
        updated_numa_topology = hardware.get_host_numa_usage_from_instance(
                resources, usage, free)
        resources['numa_topology'] = updated_numa_topology

    def _update_usage_from_migration(self, context, instance, image_meta,
                                     resources, migration):
        """Update usage for a single migration.  The record may
        represent an incoming or outbound migration.
        """
        uuid = migration.instance_uuid
        LOG.info(_LI("Updating from migration %s") % uuid)

        incoming = (migration.dest_compute == self.host and
                    migration.dest_node == self.nodename)
        outbound = (migration.source_compute == self.host and
                    migration.source_node == self.nodename)
        same_node = (incoming and outbound)

        record = self.tracked_instances.get(uuid, None)
        itype = None

        if same_node:
            # same node resize. record usage for whichever instance type the
            # instance is *not* in:
            if (instance['instance_type_id'] ==
                    migration.old_instance_type_id):
                itype = self._get_instance_type(context, instance, 'new_',
                        migration.new_instance_type_id)
            else:
                # instance record already has new flavor, hold space for a
                # possible revert to the old instance type:
                itype = self._get_instance_type(context, instance, 'old_',
                        migration.old_instance_type_id)

        elif incoming and not record:
            # instance has not yet migrated here:
            itype = self._get_instance_type(context, instance, 'new_',
                    migration.new_instance_type_id)

        elif outbound and not record:
            # instance migrated, but record usage for a possible revert:
            itype = self._get_instance_type(context, instance, 'old_',
                    migration.old_instance_type_id)

        if image_meta is None:
            image_meta = utils.get_image_from_system_metadata(
                    instance['system_metadata'])

        if itype:
            host_topology = resources.get('numa_topology')
            if host_topology:
                host_topology = objects.NUMATopology.obj_from_db_obj(
                        host_topology)
            numa_topology = hardware.numa_get_constraints(itype, image_meta)
            numa_topology = (
                    hardware.numa_fit_instance_to_host(
                        host_topology, numa_topology))
            usage = self._get_usage_dict(
                        itype, numa_topology=numa_topology)
            if self.pci_tracker:
                self.pci_tracker.update_pci_for_migration(context, instance)
            self._update_usage(context, resources, usage)
            if self.pci_tracker:
                resources['pci_device_pools'] = self.pci_tracker.stats
            else:
                resources['pci_device_pools'] = []
            self.tracked_migrations[uuid] = (migration, itype)

    def _update_usage_from_migrations(self, context, resources, migrations):

        self.tracked_migrations.clear()

        filtered = {}

        # do some defensive filtering against bad migrations records in the
        # database:
        for migration in migrations:
            try:
                instance = migration.instance
            except exception.InstanceNotFound as e:
                # migration referencing deleted instance
                LOG.debug('Migration instance not found: %s', e)
                continue

            uuid = instance.uuid

            # skip migration if instance isn't in a resize state:
            if not self._instance_in_resize_state(instance):
                LOG.warning(_LW("Instance not resizing, skipping migration."),
                            instance_uuid=uuid)
                continue

            # filter to most recently updated migration for each instance:
            m = filtered.get(uuid, None)
            if not m or migration.updated_at >= m.updated_at:
                filtered[uuid] = migration

        for migration in filtered.values():
            instance = migration.instance
            try:
                self._update_usage_from_migration(context, instance, None,
                                                  resources, migration)
            except exception.FlavorNotFound:
                LOG.warning(_LW("Flavor could not be found, skipping "
                                "migration."), instance_uuid=uuid)
                continue

    def _update_usage_from_instance(self, context, resources, instance):
        """Update usage for a single instance."""

        uuid = instance['uuid']
        is_new_instance = uuid not in self.tracked_instances
        is_deleted_instance = instance['vm_state'] == vm_states.DELETED

        if is_new_instance:
            self.tracked_instances[uuid] = instance_obj.compat_instance(
                instance)
            sign = 1

        if is_deleted_instance:
            self.tracked_instances.pop(uuid)
            sign = -1

        self.stats.update_stats_for_instance(instance)

        if self.pci_tracker:
            self.pci_tracker.update_pci_for_instance(context, instance)

        # if it's a new or deleted instance:
        if is_new_instance or is_deleted_instance:
            # new instance, update compute node resource usage:
            self._update_usage(context, resources, instance, sign=sign)

        resources['current_workload'] = self.stats.calculate_workload()
        if self.pci_tracker:
            resources['pci_device_pools'] = self.pci_tracker.stats
        else:
            resources['pci_device_pools'] = []

    def _update_usage_from_instances(self, context, resources, instances):
        """Calculate resource usage based on instance utilization.  This is
        different than the hypervisor's view as it will account for all
        instances assigned to the local compute host, even if they are not
        currently powered on.
        """
        self.tracked_instances.clear()

        # purge old stats and init with anything passed in by the driver
        self.stats.clear()
        self.stats.digest_stats(resources.get('stats'))

        # set some initial values, reserve room for host/hypervisor:
        resources['local_gb_used'] = CONF.reserved_host_disk_mb / 1024
        resources['memory_mb_used'] = CONF.reserved_host_memory_mb
        resources['free_ram_mb'] = (resources['memory_mb'] -
                                    resources['memory_mb_used'])
        resources['free_disk_gb'] = (resources['local_gb'] -
                                     resources['local_gb_used'])
        resources['current_workload'] = 0
        resources['running_vms'] = 0

        # Reset values for extended resources
        self.ext_resources_handler.reset_resources(resources, self.driver)

        for instance in instances:
            if instance.vm_state != vm_states.DELETED:
                self._update_usage_from_instance(context, resources, instance)

    def _find_orphaned_instances(self):
        """Given the set of instances and migrations already account for
        by resource tracker, sanity check the hypervisor to determine
        if there are any "orphaned" instances left hanging around.

        Orphans could be consuming memory and should be accounted for in
        usage calculations to guard against potential out of memory
        errors.
        """
        uuids1 = frozenset(self.tracked_instances.keys())
        uuids2 = frozenset(self.tracked_migrations.keys())
        uuids = uuids1 | uuids2

        usage = self.driver.get_per_instance_usage()
        vuuids = frozenset(usage.keys())

        orphan_uuids = vuuids - uuids
        orphans = [usage[uuid] for uuid in orphan_uuids]

        return orphans

    def _update_usage_from_orphans(self, context, resources, orphans):
        """Include orphaned instances in usage."""
        for orphan in orphans:
            memory_mb = orphan['memory_mb']

            LOG.warning(_LW("Detected running orphan instance: %(uuid)s "
                            "(consuming %(memory_mb)s MB memory)"),
                        {'uuid': orphan['uuid'], 'memory_mb': memory_mb})

            # just record memory usage for the orphan
            usage = {'memory_mb': memory_mb}
            self._update_usage(context, resources, usage)

    def _verify_resources(self, resources):
        resource_keys = ["vcpus", "memory_mb", "local_gb", "cpu_info",
                         "vcpus_used", "memory_mb_used", "local_gb_used",
                         "numa_topology"]

        missing_keys = [k for k in resource_keys if k not in resources]
        if missing_keys:
            reason = _("Missing keys: %s") % missing_keys
            raise exception.InvalidInput(reason=reason)

    def _instance_in_resize_state(self, instance):
        vm = instance['vm_state']
        task = instance['task_state']

        if vm == vm_states.RESIZED:
            return True

        if (vm in [vm_states.ACTIVE, vm_states.STOPPED]
                and task in [task_states.RESIZE_PREP,
                task_states.RESIZE_MIGRATING, task_states.RESIZE_MIGRATED,
                task_states.RESIZE_FINISH]):
            return True

        return False

    def _get_instance_type(self, context, instance, prefix,
            instance_type_id=None):
        """Get the instance type from sys metadata if it's stashed.  If not,
        fall back to fetching it via the object API.

        See bug 1164110
        """
        try:
            extracted_flavor = flavors.extract_flavor(instance, prefix)
        except KeyError:
            if not instance_type_id:
                instance_type_id = instance['instance_type_id']
            return objects.Flavor.get_by_id(context, instance_type_id)
        return extracted_flavor

    def _get_usage_dict(self, object_or_dict, **updates):
        """Make a usage dict _update methods expect.

        Accepts a dict or an Instance or Flavor object, and a set of updates.
        Converts the object to a dict and applies the updates.

        :param object_or_dict: instance or flavor as an object or just a dict
        :param updates: key-value pairs to update the passed object.
                        Currently only considers 'numa_topology', all other
                        keys are ignored.

        :returns: a dict with all the information from object_or_dict updated
                  with updates
        """
        usage = {}
        if isinstance(object_or_dict, objects.Instance):
            usage = instance_obj.compat_instance(object_or_dict)
        elif isinstance(object_or_dict, objects.Flavor):
            usage = obj_base.obj_to_primitive(object_or_dict)
        else:
            usage.update(object_or_dict)

        for key in ('numa_topology',):
            if key in updates:
                usage[key] = updates[key]
        return usage
