text: # 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_log import log as logging
  from oslo_serialization import jsonutils
  from oslo_utils import importutils
  
  from nova.compute import claims
  from nova.compute import monitors
  from nova.compute import task_states
  from nova.compute import vm_states
  import nova.conf
  from nova import exception
  from nova.i18n import _, _LE, _LI, _LW
  from nova import objects
  from nova.objects import base as obj_base
  from nova.objects import migration as migration_obj
  from nova.pci import manager as pci_manager
  from nova import rpc
  from nova.scheduler import client as scheduler_client
  from nova import utils
  from nova.virt import hardware
  
  CONF = nova.conf.CONF
  
  LOG = logging.getLogger(__name__)
  COMPUTE_RESOURCE_SEMAPHORE = "compute_resources"
  
  
  def _instance_in_resize_state(instance):
      """Returns True if the instance is in one of the resizing states.
  
      :param instance: `nova.objects.Instance` object
      """
      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, task_states.REBUILDING]):
          return True
  
      return False
  
  
  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.nodename = nodename
          self.compute_node = None
          self.stats = importutils.import_object(CONF.compute_stats_class)
          self.tracked_instances = {}
          self.tracked_migrations = {}
          monitor_handler = monitors.MonitorHandler(self)
          self.monitors = monitor_handler.monitors
          self.old_resources = objects.ComputeNode()
          self.scheduler_client = scheduler_client.SchedulerClient()
          self.ram_allocation_ratio = CONF.ram_allocation_ratio
          self.cpu_allocation_ratio = CONF.cpu_allocation_ratio
          self.disk_allocation_ratio = CONF.disk_allocation_ratio
  
      @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.
          :type instance_ref: nova.objects.instance.Instance object
          :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(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 the 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']})
          LOG.debug("Disk overhead for %(flavor)d GB instance; %(overhead)d "
                    "GB", {'flavor': instance_ref.root_gb,
                           'overhead': overhead.get('disk_gb', 0)})
  
          pci_requests = objects.InstancePCIRequests.get_by_instance_uuid(
              context, instance_ref.uuid)
          claim = claims.Claim(context, instance_ref, self, self.compute_node,
                               pci_requests, 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_numa_topology = claim.claimed_numa_topology
          instance_ref.numa_topology = instance_numa_topology
          self._set_instance_host_and_node(instance_ref)
  
          if self.pci_tracker:
              # NOTE(jaypipes): ComputeNode.pci_device_pools is set below
              # in _update_usage_from_instance().
              self.pci_tracker.claim_instance(context, pci_requests,
                                              instance_numa_topology)
  
          # Mark resources in-use and update stats
          self._update_usage_from_instance(context, instance_ref)
  
          elevated = context.elevated()
          # persist changes to the compute node:
          self._update(elevated)
  
          return claim
  
      @utils.synchronized(COMPUTE_RESOURCE_SEMAPHORE)
      def rebuild_claim(self, context, instance, limits=None, image_meta=None,
                        migration=None):
          """Create a claim for a rebuild operation."""
          instance_type = instance.flavor
          return self._move_claim(context, instance, instance_type,
                                  move_type='evacuation', limits=limits,
                                  image_meta=image_meta, migration=migration)
  
      @utils.synchronized(COMPUTE_RESOURCE_SEMAPHORE)
      def resize_claim(self, context, instance, instance_type,
                       image_meta=None, limits=None):
          """Create a claim for a resize or cold-migration move."""
          return self._move_claim(context, instance, instance_type,
                                  image_meta=image_meta, limits=limits)
  
      def _move_claim(self, context, instance, new_instance_type, move_type=None,
                      image_meta=None, limits=None, migration=None):
          """Indicate that resources are needed for a move to this host.
  
          Move can be either a migrate/resize, live-migrate or an
          evacuate/rebuild operation.
  
          :param context: security context
          :param instance: instance object to reserve resources for
          :param new_instance_type: new instance_type being resized to
          :param image_meta: instance image metadata
          :param move_type: move type - can be one of 'migration', 'resize',
                           'live-migration', 'evacuate'
          :param limits: Dict of oversubscription limits for memory, disk,
          and CPUs
          :param migration: A migration object if one was already created
                            elsewhere for this operation
          :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 migration:
              self._claim_existing_migration(migration)
          else:
              migration = self._create_migration(context, instance,
                                                 new_instance_type, move_type)
  
          if self.disabled:
              # compute_driver doesn't support resource tracking, just
              # generate the migration record and continue the resize:
              return claims.NopClaim(migration=migration)
  
          # get memory overhead required to build this instance:
          overhead = self.driver.estimate_instance_overhead(new_instance_type)
          LOG.debug("Memory overhead for %(flavor)d MB instance; %(overhead)d "
                    "MB", {'flavor': new_instance_type.memory_mb,
                            'overhead': overhead['memory_mb']})
          LOG.debug("Disk overhead for %(flavor)d GB instance; %(overhead)d "
                    "GB", {'flavor': instance.root_gb,
                           'overhead': overhead.get('disk_gb', 0)})
  
          pci_requests = objects.InstancePCIRequests.\
                         get_by_instance_uuid_and_newness(
                             context, instance.uuid, True)
          claim = claims.MoveClaim(context, instance, new_instance_type,
                                   image_meta, self, self.compute_node,
                                   pci_requests, overhead=overhead,
                                   limits=limits)
          claim.migration = migration
          instance.migration_context = claim.create_migration_context()
          instance.save()
  
          # Mark the resources in-use for the resize landing on this
          # compute host:
          self._update_usage_from_migration(context, instance, image_meta,
                                            migration)
          elevated = context.elevated()
          self._update(elevated)
  
          return claim
  
      def _create_migration(self, context, instance, new_instance_type,
                            move_type=None):
          """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.
          """
          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 = instance.flavor.id
          migration.new_instance_type_id = new_instance_type.id
          migration.status = 'pre-migrating'
          migration.instance_uuid = instance.uuid
          migration.source_compute = instance.host
          migration.source_node = instance.node
          if move_type:
              migration.migration_type = move_type
          else:
              migration.migration_type = migration_obj.determine_migration_type(
                  migration)
          migration.create()
          return migration
  
      def _claim_existing_migration(self, migration):
          """Make an existing migration record count for resource tracking.
  
          If a migration record was created already before the request made
          it to this compute host, only set up the migration so it's included in
          resource tracking. This should be done while the
          COMPUTE_RESOURCES_SEMAPHORE is held.
          """
          migration.dest_compute = self.host
          migration.dest_node = self.nodename
          migration.dest_host = self.driver.get_host_ip_addr()
          migration.status = 'pre-migrating'
          migration.save()
  
      def _set_instance_host_and_node(self, 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()
  
      def _unset_instance_host_and_node(self, instance):
          """Untag the instance so it no longer belongs to the 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 = None
          instance.node = None
          instance.save()
  
      @utils.synchronized(COMPUTE_RESOURCE_SEMAPHORE)
      def abort_instance_claim(self, context, instance):
          """Remove usage from the given instance."""
          self._update_usage_from_instance(context, instance, is_removed=True)
  
          instance.clear_numa_topology()
          self._unset_instance_host_and_node(instance)
  
          self._update(context.elevated())
  
      @utils.synchronized(COMPUTE_RESOURCE_SEMAPHORE)
      def drop_move_claim(self, context, instance, instance_type=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,
                                                          migration)
  
              if instance_type is not None and instance_type.id == itype['id']:
                  numa_topology = self._get_migration_context_resource(
                      'numa_topology', instance)
                  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(usage, sign=-1)
  
                  ctxt = context.elevated()
                  self._update(ctxt)
  
              instance.drop_migration_context()
  
      @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, instance)
              self._update(context.elevated())
  
      @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 just use resources
          # to initialize
          if self.compute_node:
              self._copy_resources(resources)
              self._setup_pci_tracker(context, resources)
              return
  
          # now try to get the compute node record from the
          # database. If we get one we use resources to initialize
          self.compute_node = self._get_compute_node(context)
          if self.compute_node:
              self._copy_resources(resources)
              self._setup_pci_tracker(context, resources)
              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.
          self.compute_node = objects.ComputeNode(context)
          self.compute_node.host = self.host
          self._copy_resources(resources)
          self.compute_node.create()
          LOG.info(_LI('Compute_service record created for '
                       '%(host)s:%(node)s'),
                   {'host': self.host, 'node': self.nodename})
  
          self._setup_pci_tracker(context, resources)
  
      def _setup_pci_tracker(self, context, resources):
          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)
              if 'pci_passthrough_devices' in resources:
                  dev_json = resources.pop('pci_passthrough_devices')
                  self.pci_tracker.update_devices_from_hypervisor_resources(
                          dev_json)
  
              dev_pools_obj = self.pci_tracker.stats.to_device_pools_obj()
              self.compute_node.pci_device_pools = dev_pools_obj
  
      def _copy_resources(self, resources):
          """Copy resource values to initialise compute_node and related
          data structures.
          """
          # purge old stats and init with anything passed in by the driver
          self.stats.clear()
          self.stats.digest_stats(resources.get('stats'))
          self.compute_node.stats = copy.deepcopy(self.stats)
  
          # update the allocation ratios for the related ComputeNode object
          self.compute_node.ram_allocation_ratio = self.ram_allocation_ratio
          self.compute_node.cpu_allocation_ratio = self.cpu_allocation_ratio
          self.compute_node.disk_allocation_ratio = self.disk_allocation_ratio
  
          # now copy rest to compute_node
          self.compute_node.update_from_virt_driver(resources)
  
      def _get_host_metrics(self, context, nodename):
          """Get the metrics from monitors and
          notify information to message bus.
          """
          metrics = objects.MonitorMetricList()
          metrics_info = {}
          for monitor in self.monitors:
              try:
                  monitor.add_metrics_to_list(metrics)
              except Exception as exc:
                  LOG.warning(_LW("Cannot get the metrics from %(mon)s; "
                                  "error: %(exc)s"),
                              {'mon': monitor, 'exc': exc})
          # TODO(jaypipes): Remove this when compute_node.metrics doesn't need
          # to be populated as a JSON-ified string.
          metrics = metrics.to_list()
          if len(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)
          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"] = ''
  
          self._verify_resources(resources)
  
          self._report_hypervisor_resource_view(resources)
  
          self._update_available_resource(context, resources)
  
      def _pair_instances_to_migrations(self, migrations, instances):
          instance_by_uuid = {inst.uuid: inst for inst in instances}
          for migration in migrations:
              try:
                  migration.instance = instance_by_uuid[migration.instance_uuid]
              except KeyError:
                  # NOTE(danms): If this happens, we don't set it here, and
                  # let the code either fail or lazy-load the instance later
                  # which is what happened before we added this optimization.
                  # This _should_ not be possible, of course.
                  LOG.error(_LE('Migration for instance %(uuid)s refers to '
                                'another host\'s instance!'),
                            {'uuid': migration.instance_uuid})
  
      @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
  
          # 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',
                              'flavor', 'migration_context'])
  
          # Now calculate usage based on instance utilization:
          self._update_usage_from_instances(context, instances)
  
          # Grab all in-progress migrations:
          migrations = objects.MigrationList.get_in_progress_by_host_and_node(
                  context, self.host, self.nodename)
  
          self._pair_instances_to_migrations(migrations, instances)
          self._update_usage_from_migrations(context, 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(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.
          self.pci_tracker.clean_usage(instances, migrations, orphans)
          dev_pools_obj = self.pci_tracker.stats.to_device_pools_obj()
          self.compute_node.pci_device_pools = dev_pools_obj
  
          self._report_final_resource_view()
  
          metrics = self._get_host_metrics(context, self.nodename)
          # TODO(pmurray): metrics should not be a json string in ComputeNode,
          # but it is. This should be changed in ComputeNode
          self.compute_node.metrics = jsonutils.dumps(metrics)
  
          # update the compute_node
          self._update(context)
          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:
              return objects.ComputeNode.get_by_host_and_nodename(
                  context, self.host, self.nodename)
          except exception.NotFound:
              LOG.warning(_LW("No compute node record for %(host)s:%(node)s"),
                          {'host': self.host, 'node': self.nodename})
  
      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):
          """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 = self.compute_node.vcpus
          if vcpus:
              tcpu = vcpus
              ucpu = self.compute_node.vcpus_used
              LOG.info(_LI("Total usable vcpus: %(tcpu)s, "
                          "total allocated vcpus: %(ucpu)s"),
                          {'tcpu': vcpus,
                           'ucpu': ucpu})
          else:
              tcpu = 0
              ucpu = 0
          pci_stats = (list(self.compute_node.pci_device_pools) if
              self.compute_node.pci_device_pools else [])
          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': self.compute_node.memory_mb,
                    'used_ram': self.compute_node.memory_mb_used,
                    'phys_disk': self.compute_node.local_gb,
                    'used_disk': self.compute_node.local_gb_used,
                    'total_vcpus': tcpu,
                    'used_vcpus': ucpu,
                    'pci_stats': pci_stats})
  
      def _resource_change(self):
          """Check to see if any resources have changed."""
          if not obj_base.obj_equal_prims(self.compute_node, self.old_resources):
              self.old_resources = copy.deepcopy(self.compute_node)
              return True
          return False
  
      def _update(self, context):
          """Update partial stats locally and populate them to Scheduler."""
          if not self._resource_change():
              return
          # Persist the stats to the Scheduler
          self.scheduler_client.update_resource_stats(self.compute_node)
          if self.pci_tracker:
              self.pci_tracker.save(context)
  
      def _update_usage(self, usage, sign=1):
          mem_usage = usage['memory_mb']
          disk_usage = usage.get('root_gb', 0)
  
          overhead = self.driver.estimate_instance_overhead(usage)
          mem_usage += overhead['memory_mb']
          disk_usage += overhead.get('disk_gb', 0)
  
          self.compute_node.memory_mb_used += sign * mem_usage
          self.compute_node.local_gb_used += sign * disk_usage
          self.compute_node.local_gb_used += sign * usage.get('ephemeral_gb', 0)
          self.compute_node.vcpus_used += sign * usage.get('vcpus', 0)
  
          # free ram and disk may be negative, depending on policy:
          self.compute_node.free_ram_mb = (self.compute_node.memory_mb -
                                           self.compute_node.memory_mb_used)
          self.compute_node.free_disk_gb = (self.compute_node.local_gb -
                                            self.compute_node.local_gb_used)
  
          self.compute_node.running_vms = self.stats.num_instances
  
          # Calculate the numa usage
          free = sign == -1
          updated_numa_topology = hardware.get_host_numa_usage_from_instance(
                  self.compute_node, usage, free)
          self.compute_node.numa_topology = updated_numa_topology
  
      def _is_trackable_migration(self, migration):
          # Only look at resize/migrate migration and evacuation records
          # NOTE(danms): RT should probably examine live migration
          # records as well and do something smart. However, ignore
          # those for now to avoid them being included in below calculations.
          return migration.migration_type in ('resize', 'migration',
                                              'evacuation')
  
      def _get_migration_context_resource(self, resource, instance,
                                          prefix='new_', itype=None):
          migration_context = instance.migration_context
          if migration_context:
              return getattr(migration_context, prefix + resource)
          else:
              return None
  
      def _update_usage_from_migration(self, context, instance, image_meta,
                                       migration):
          """Update usage for a single migration.  The record may
          represent an incoming or outbound migration.
          """
          if not self._is_trackable_migration(migration):
              return
  
          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
          numa_topology = 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)
                  numa_topology = self._get_migration_context_resource(
                      'numa_topology', instance)
              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)
                  numa_topology = self._get_migration_context_resource(
                      'numa_topology', instance, prefix='old_')
  
          elif incoming and not record:
              # instance has not yet migrated here:
              itype = self._get_instance_type(context, instance, 'new_',
                      migration)
              numa_topology = self._get_migration_context_resource(
                  'numa_topology', instance)
  
          elif outbound and not record:
              # instance migrated, but record usage for a possible revert:
              itype = self._get_instance_type(context, instance, 'old_',
                      migration)
              numa_topology = self._get_migration_context_resource(
                  'numa_topology', instance, prefix='old_')
  
          if image_meta is None:
              image_meta = objects.ImageMeta.from_instance(instance)
          # TODO(jaypipes): Remove when image_meta is always passed
          # as an objects.ImageMeta
          elif not isinstance(image_meta, objects.ImageMeta):
              image_meta = objects.ImageMeta.from_dict(image_meta)
  
          if itype:
              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(usage)
              if self.pci_tracker:
                  obj = self.pci_tracker.stats.to_device_pools_obj()
                  self.compute_node.pci_device_pools = obj
              else:
                  obj = objects.PciDevicePoolList()
                  self.compute_node.pci_device_pools = obj
              self.tracked_migrations[uuid] = (migration, itype)
  
      def _update_usage_from_migrations(self, context, migrations):
          filtered = {}
          instances = {}
          self.tracked_migrations.clear()
  
          # do some defensive filtering against bad migrations records in the
          # database:
          for migration in migrations:
              uuid = migration.instance_uuid
  
              try:
                  if uuid not in instances:
                      instances[uuid] = migration.instance
              except exception.InstanceNotFound as e:
                  # migration referencing deleted instance
                  LOG.debug('Migration instance not found: %s', e)
                  continue
  
              # skip migration if instance isn't in a resize state:
              if not _instance_in_resize_state(instances[uuid]):
                  LOG.warning(_LW("Instance not resizing, skipping migration."),
                              instance_uuid=uuid)
                  continue
  
              # filter to most recently updated migration for each instance:
              other_migration = filtered.get(uuid, None)
              # NOTE(claudiub): In Python 3, you cannot compare NoneTypes.
              if (not other_migration or (
                      migration.updated_at and other_migration.updated_at and
                      migration.updated_at >= other_migration.updated_at)):
                  filtered[uuid] = migration
  
          for migration in filtered.values():
              instance = instances[migration.instance_uuid]
              try:
                  self._update_usage_from_migration(context, instance, None,
                                                    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, instance, is_removed=False):
          """Update usage for a single instance."""
  
          uuid = instance['uuid']
          is_new_instance = uuid not in self.tracked_instances
          is_removed_instance = (
                  is_removed or
                  instance['vm_state'] in vm_states.ALLOW_RESOURCE_REMOVAL)
  
          if is_new_instance:
              self.tracked_instances[uuid] = obj_base.obj_to_primitive(instance)
              sign = 1
  
          if is_removed_instance:
              self.tracked_instances.pop(uuid)
              sign = -1
  
          self.stats.update_stats_for_instance(instance, is_removed_instance)
          self.compute_node.stats = copy.deepcopy(self.stats)
  
          # if it's a new or deleted instance:
          if is_new_instance or is_removed_instance:
              if self.pci_tracker:
                  self.pci_tracker.update_pci_for_instance(context,
                                                           instance,
                                                           sign=sign)
              # new instance, update compute node resource usage:
              self._update_usage(instance, sign=sign)
  
          self.compute_node.current_workload = self.stats.calculate_workload()
          if self.pci_tracker:
              obj = self.pci_tracker.stats.to_device_pools_obj()
              self.compute_node.pci_device_pools = obj
          else:
              self.compute_node.pci_device_pools = objects.PciDevicePoolList()
  
      def _update_usage_from_instances(self, context, 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()
  
          # set some initial values, reserve room for host/hypervisor:
          self.compute_node.local_gb_used = CONF.reserved_host_disk_mb / 1024
          self.compute_node.memory_mb_used = CONF.reserved_host_memory_mb
          self.compute_node.vcpus_used = 0
          self.compute_node.free_ram_mb = (self.compute_node.memory_mb -
                                           self.compute_node.memory_mb_used)
          self.compute_node.free_disk_gb = (self.compute_node.local_gb -
                                            self.compute_node.local_gb_used)
          self.compute_node.current_workload = 0
          self.compute_node.running_vms = 0
  
          for instance in instances:
              if instance.vm_state not in vm_states.ALLOW_RESOURCE_REMOVAL:
                  self._update_usage_from_instance(context, instance)
          self.compute_node.free_ram_mb = max(0, self.compute_node.free_ram_mb)
          self.compute_node.free_disk_gb = max(0, self.compute_node.free_disk_gb)
  
      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, 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(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 _get_instance_type(self, context, instance, prefix, migration):
          """Get the instance type from instance."""
          stashed_flavors = migration.migration_type in ('resize',)
          if stashed_flavors:
              return getattr(instance, '%sflavor' % prefix)
          else:
              # NOTE(ndipanov): Certain migration types (all but resize)
              # do not change flavors so there is no need to stash
              # them. In that case - just get the instance flavor.
              return instance.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 = obj_base.obj_to_primitive(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
  