text: # Copyright 2010 United States Government as represented by the
  # Administrator of the National Aeronautics and Space Administration.
  # 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.
  
  """Base Manager class.
  
  Managers are responsible for a certain aspect of the system.  It is a logical
  grouping of code relating to a portion of the system.  In general other
  components should be using the manager to make changes to the components that
  it is responsible for.
  
  For example, other components that need to deal with volumes in some way,
  should do so by calling methods on the VolumeManager instead of directly
  changing fields in the database.  This allows us to keep all of the code
  relating to volumes in the same place.
  
  We have adopted a basic strategy of Smart managers and dumb data, which means
  rather than attaching methods to data objects, components should call manager
  methods that act on the data.
  
  Methods on managers that can be executed locally should be called directly. If
  a particular method must execute on a remote host, this should be done via rpc
  to the service that wraps the manager
  
  Managers should be responsible for most of the db access, and
  non-implementation specific data.  Anything implementation specific that can't
  be generalized should be done by the Driver.
  
  In general, we prefer to have one manager with multiple drivers for different
  implementations, but sometimes it makes sense to have multiple managers.  You
  can think of it this way: Abstract different overall strategies at the manager
  level(FlatNetwork vs VlanNetwork), and different implementations at the driver
  level(LinuxNetDriver vs CiscoNetDriver).
  
  Managers will often provide methods for initial setup of a host or periodic
  tasks to a wrapping service.
  
  This module provides Manager, a base class for managers.
  
  """
  
  
  from oslo import messaging
  from oslo_config import cfg
  
  from cinder.db import base
  from cinder.openstack.common import log as logging
  from cinder.openstack.common import periodic_task
  from cinder.scheduler import rpcapi as scheduler_rpcapi
  from cinder import version
  
  
  CONF = cfg.CONF
  LOG = logging.getLogger(__name__)
  
  
  class Manager(base.Base, periodic_task.PeriodicTasks):
      # Set RPC API version to 1.0 by default.
      RPC_API_VERSION = '1.0'
  
      target = messaging.Target(version=RPC_API_VERSION)
  
      def __init__(self, host=None, db_driver=None):
          if not host:
              host = CONF.host
          self.host = host
          self.additional_endpoints = []
          super(Manager, self).__init__(db_driver)
  
      def periodic_tasks(self, context, raise_on_error=False):
          """Tasks to be run at a periodic interval."""
          return self.run_periodic_tasks(context, raise_on_error=raise_on_error)
  
      def init_host(self):
          """Handle initialization if this is a standalone service.
  
          Child classes should override this method.
  
          """
          pass
  
      def service_version(self, context):
          return version.version_string()
  
      def service_config(self, context):
          config = {}
          for key in CONF:
              config[key] = CONF.get(key, None)
          return config
  
  
  class SchedulerDependentManager(Manager):
      """Periodically send capability updates to the Scheduler services.
  
      Services that need to update the Scheduler of their capabilities
      should derive from this class. Otherwise they can derive from
      manager.Manager directly. Updates are only sent after
      update_service_capabilities is called with non-None values.
  
      """
  
      def __init__(self, host=None, db_driver=None, service_name='undefined'):
          self.last_capabilities = None
          self.service_name = service_name
          self.scheduler_rpcapi = scheduler_rpcapi.SchedulerAPI()
          super(SchedulerDependentManager, self).__init__(host, db_driver)
  
      def update_service_capabilities(self, capabilities):
          """Remember these capabilities to send on next periodic update."""
          self.last_capabilities = capabilities
  
      @periodic_task.periodic_task
      def _publish_service_capabilities(self, context):
          """Pass data back to the scheduler at a periodic interval."""
          if self.last_capabilities:
              LOG.debug('Notifying Schedulers of capabilities ...')
              self.scheduler_rpcapi.update_service_capabilities(
                  context,
                  self.service_name,
                  self.host,
                  self.last_capabilities)
  