text: # Copyright (c) 2011-2012 OpenStack Foundation
  # Copyright (c) 2012 Canonical Ltd
  # Copyright (c) 2012 SUSE LINUX Products GmbH
  # 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.
  from distutils import versionpredicate
  
  from oslo_log import log as logging
  from oslo_utils import versionutils
  
  from nova.objects import fields
  from nova.scheduler import filters
  
  
  LOG = logging.getLogger(__name__)
  
  
  class ImagePropertiesFilter(filters.BaseHostFilter):
      """Filter compute nodes that satisfy instance image properties.
  
      The ImagePropertiesFilter filters compute nodes that satisfy
      any architecture, hypervisor type, or virtual machine mode properties
      specified on the instance's image properties.  Image properties are
      contained in the image dictionary in the request_spec.
      """
  
      # Image Properties and Compute Capabilities do not change within
      # a request
      run_filter_once_per_request = True
  
      def _instance_supported(self, host_state, image_props,
                              hypervisor_version):
          img_arch = image_props.get('hw_architecture')
          img_h_type = image_props.get('img_hv_type')
          img_vm_mode = image_props.get('hw_vm_mode')
          checked_img_props = (
              fields.Architecture.canonicalize(img_arch),
              fields.HVType.canonicalize(img_h_type),
              fields.VMMode.canonicalize(img_vm_mode)
          )
  
          # Supported if no compute-related instance properties are specified
          if not any(checked_img_props):
              return True
  
          supp_instances = host_state.supported_instances
          # Not supported if an instance property is requested but nothing
          # advertised by the host.
          if not supp_instances:
              LOG.debug("Instance contains properties %(image_props)s, "
                          "but no corresponding supported_instances are "
                          "advertised by the compute node",
                        {'image_props': image_props})
              return False
  
          def _compare_props(props, other_props):
              for i in props:
                  if i and i not in other_props:
                      return False
              return True
  
          def _compare_product_version(hyper_version, image_props):
              version_required = image_props.get('img_hv_requested_version')
              if not(hypervisor_version and version_required):
                  return True
              img_prop_predicate = versionpredicate.VersionPredicate(
                  'image_prop (%s)' % version_required)
              hyper_ver_str = versionutils.convert_version_to_str(hyper_version)
              return img_prop_predicate.satisfied_by(hyper_ver_str)
  
          for supp_inst in supp_instances:
              if _compare_props(checked_img_props, supp_inst):
                  if _compare_product_version(hypervisor_version, image_props):
                      return True
  
          LOG.debug("Instance contains properties %(image_props)s "
                      "that are not provided by the compute node "
                      "supported_instances %(supp_instances)s or "
                      "hypervisor version %(hypervisor_version)s do not match",
                    {'image_props': image_props,
                     'supp_instances': supp_instances,
                     'hypervisor_version': hypervisor_version})
          return False
  
      def host_passes(self, host_state, spec_obj):
          """Check if host passes specified image properties.
  
          Returns True for compute nodes that satisfy image properties
          contained in the request_spec.
          """
          image_props = spec_obj.image.properties if spec_obj.image else {}
  
          if not self._instance_supported(host_state, image_props,
                                          host_state.hypervisor_version):
              LOG.debug("%(host_state)s does not support requested "
                          "instance_properties", {'host_state': host_state})
              return False
          return True
  