old_contents: # Copyright (c) 2015 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.
  
  import abc
  
  import six
  
  
  @six.add_metaclass(abc.ABCMeta)
  class BaseResourceFilter(object):
      """Encapsulate logic that is specific to the resource type."""
      @abc.abstractmethod
      def filter_agents(self, plugin, context, resource):
          """Return the agents that can host the resource."""
  
      def bind(self, context, agents, resource_id):
          """Bind the resource to the agents."""
          with context.session.begin(subtransactions=True):
              for agent in agents:
                  # Load is being incremented here to reflect latest agent load
                  # even within the agent report interval. This will be very
                  # much necessary when bulk resource creation happens within a
                  # agent report interval time.
                  # NOTE: The resource being bound might or might not be of the
                  # same type which is accounted for the load. It isn't a
                  # problem because "+ 1" here does not meant to predict
                  # precisely what the load of the agent will be. The value will
                  # be corrected by the agent on the next report interval.
                  agent.load += 1
                  agent.update()
  
new_contents: # Copyright (c) 2015 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.
  
  import abc
  
  from neutron_lib.db import api as db_api
  import six
  
  
  @six.add_metaclass(abc.ABCMeta)
  class BaseResourceFilter(object):
      """Encapsulate logic that is specific to the resource type."""
      @abc.abstractmethod
      def filter_agents(self, plugin, context, resource):
          """Return the agents that can host the resource."""
  
      def bind(self, context, agents, resource_id):
          """Bind the resource to the agents."""
          with db_api.CONTEXT_WRITER.using(context):
              for agent in agents:
                  # Load is being incremented here to reflect latest agent load
                  # even within the agent report interval. This will be very
                  # much necessary when bulk resource creation happens within a
                  # agent report interval time.
                  # NOTE: The resource being bound might or might not be of the
                  # same type which is accounted for the load. It isn't a
                  # problem because "+ 1" here does not meant to predict
                  # precisely what the load of the agent will be. The value will
                  # be corrected by the agent on the next report interval.
                  agent.load += 1
                  agent.update()
  
subject: Switch to new engine facade for BaseResourceFilter