old_contents: #
  #    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.
  
  ENGINE_TOPIC = 'engine'
  
  CLUSTER_KEYS = (
      CLUSTER_NAME, CLUSTER_ID, CLUSTER_PARENT,
      CLUSTER_DOMAIN, CLUSTER_PROJECT, CLUSTER_USER,
      CLUSTER_CREATED_TIME, CLUSTER_UPDATED_TIME, CLUSTER_DELETED_TIME,
      CLUSTER_STATUS, CLUSTER_STATUS_DATA,
  ) = (
      'name', 'id', 'parent',
      'domain', 'project', 'user',
      'created_time', 'updated_time', 'deleted_time',
      'status', 'status_data',
  )
  
new_contents: #
  #    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.
  
  ENGINE_TOPIC = 'engine'
  
  CLUSTER_KEYS = (
      CLUSTER_NAME, CLUSTER_PROFILE, CLUSTER_SIZE,
      CLUSTER_UUID, CLUSTER_PARENT,
      CLUSTER_DOMAIN, CLUSTER_PROJECT, CLUSTER_USER,
      CLUSTER_CREATED_TIME, CLUSTER_UPDATED_TIME, CLUSTER_DELETED_TIME,
      CLUSTER_STATUS, CLUSTER_STATUS_REASON, CLUSTER_TIMEOUT,
  ) = (
      'name', 'profile', 'size',
      'uuid', 'parent',
      'domain', 'project', 'user',
      'created_time', 'updated_time', 'deleted_time',
      'status', 'status_reason', 'timeout'
  )
  
subject: Revise cluster related key definition in rpc api based on current class implementation.