text: # Copyright 2014 Mirantis, 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.
  
  import abc
  
  from oslo_utils import timeutils
  import six
  
  from ceilometer.agent import plugin_base
  from ceilometer.compute.pollsters import util
  from ceilometer.compute.virt import inspector as virt_inspector
  
  
  @six.add_metaclass(abc.ABCMeta)
  class BaseComputePollster(plugin_base.PollsterBase):
  
      def setup_environment(self):
          super(BaseComputePollster, self).setup_environment()
          # propagate exception from check_sanity
          self.inspector.check_sanity()
  
      @property
      def inspector(self):
          try:
              inspector = self._inspector
          except AttributeError:
              inspector = virt_inspector.get_hypervisor_inspector(self.conf)
              BaseComputePollster._inspector = inspector
          return inspector
  
      @property
      def default_discovery(self):
          return 'local_instances'
  
      @staticmethod
      def _populate_cache_create(_i_cache, _instance, _inspector,
                                 _DiskData, _inspector_attr, _stats_attr):
          """Settings and return cache."""
          if _instance.id not in _i_cache:
              _data = 0
              _per_device_data = {}
              disk_rates = getattr(_inspector, _inspector_attr)(_instance)
              for disk, stats in disk_rates:
                  _data += getattr(stats, _stats_attr)
                  _per_device_data[disk.device] = (
                      getattr(stats, _stats_attr))
              _per_disk_data = {
                  _stats_attr: _per_device_data
              }
              _i_cache[_instance.id] = _DiskData(
                  _data,
                  _per_disk_data
              )
          return _i_cache[_instance.id]
  
      def _record_poll_time(self):
          """Method records current time as the poll time.
  
          :return: time in seconds since the last poll time was recorded
          """
          current_time = timeutils.utcnow()
          duration = None
          if hasattr(self, '_last_poll_time'):
              duration = timeutils.delta_seconds(self._last_poll_time,
                                                 current_time)
          self._last_poll_time = current_time
          return duration
  
      def _get_samples_per_devices(self, attribute, instance, _name, _type,
                                   _unit):
          samples = []
          for disk, value in six.iteritems(attribute):
              samples.append(util.make_sample_from_instance(
                  self.conf,
                  instance,
                  name=_name,
                  type=_type,
                  unit=_unit,
                  volume=value,
                  resource_id="%s-%s" % (instance.id, disk),
                  additional_metadata={'disk_name': disk},
              ))
          return samples
  