text: # vim: tabstop=4 shiftwidth=4 softtabstop=4
  
  # Copyright (c) 2010 OpenStack, LLC.
  # 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.
  
  """
  Scheduler base class that all Schedulers should inherit from
  """
  
  import sys
  
  from nova.compute import api as compute_api
  from nova.compute import power_state
  from nova.compute import rpcapi as compute_rpcapi
  from nova.compute import utils as compute_utils
  from nova.compute import vm_states
  from nova import db
  from nova import exception
  from nova import flags
  from nova import notifications
  from nova.openstack.common import cfg
  from nova.openstack.common import importutils
  from nova.openstack.common import log as logging
  from nova.openstack.common.notifier import api as notifier
  from nova.openstack.common import rpc
  from nova.openstack.common import timeutils
  from nova import utils
  
  
  LOG = logging.getLogger(__name__)
  
  scheduler_driver_opts = [
      cfg.StrOpt('scheduler_host_manager',
                 default='nova.scheduler.host_manager.HostManager',
                 help='The scheduler host manager class to use'),
      cfg.IntOpt('scheduler_max_attempts',
                 default=3,
                 help='Maximum number of attempts to schedule an instance'),
      ]
  
  FLAGS = flags.FLAGS
  FLAGS.register_opts(scheduler_driver_opts)
  
  flags.DECLARE('instances_path', 'nova.compute.manager')
  flags.DECLARE('libvirt_type', 'nova.virt.libvirt.driver')
  
  
  def handle_schedule_error(context, ex, instance_uuid, request_spec):
      if not isinstance(ex, exception.NoValidHost):
          LOG.exception(_("Exception during scheduler.run_instance"))
      compute_utils.add_instance_fault_from_exc(context,
              instance_uuid, ex, sys.exc_info())
      state = vm_states.ERROR.upper()
      LOG.warning(_('Setting instance to %(state)s state.'),
                  locals(), instance_uuid=instance_uuid)
  
      # update instance state and notify on the transition
      (old_ref, new_ref) = db.instance_update_and_get_original(context,
              instance_uuid, {'vm_state': vm_states.ERROR,
                              'task_state': None})
      notifications.send_update(context, old_ref, new_ref,
              service="scheduler")
  
      properties = request_spec.get('instance_properties', {})
      payload = dict(request_spec=request_spec,
                     instance_properties=properties,
                     instance_id=instance_uuid,
                     state=vm_states.ERROR,
                     method='run_instance',
                     reason=ex)
  
      notifier.notify(context, notifier.publisher_id("scheduler"),
                      'scheduler.run_instance', notifier.ERROR, payload)
  
  
  def cast_to_volume_host(context, host, method, **kwargs):
      """Cast request to a volume host queue"""
  
      volume_id = kwargs.get('volume_id', None)
      if volume_id is not None:
          now = timeutils.utcnow()
          db.volume_update(context, volume_id,
                  {'host': host, 'scheduled_at': now})
      rpc.cast(context,
               rpc.queue_get_for(context, 'volume', host),
               {"method": method, "args": kwargs})
      LOG.debug(_("Casted '%(method)s' to volume '%(host)s'") % locals())
  
  
  def instance_update_db(context, instance_uuid, host):
      '''Set the host and scheduled_at fields of an Instance.
  
      :returns: An Instance with the updated fields set properly.
      '''
      now = timeutils.utcnow()
      values = {'host': host, 'scheduled_at': now}
      return db.instance_update(context, instance_uuid, values)
  
  
  def cast_to_compute_host(context, host, method, **kwargs):
      """Cast request to a compute host queue"""
  
      instance_uuid = kwargs.get('instance_uuid', None)
      if instance_uuid:
          instance_update_db(context, instance_uuid, host)
  
      rpc.cast(context,
               rpc.queue_get_for(context, 'compute', host),
               {"method": method, "args": kwargs})
      LOG.debug(_("Casted '%(method)s' to compute '%(host)s'") % locals())
  
  
  def cast_to_network_host(context, host, method, **kwargs):
      """Cast request to a network host queue"""
  
      rpc.cast(context,
               rpc.queue_get_for(context, 'network', host),
               {"method": method, "args": kwargs})
      LOG.debug(_("Casted '%(method)s' to network '%(host)s'") % locals())
  
  
  def cast_to_host(context, topic, host, method, **kwargs):
      """Generic cast to host"""
  
      topic_mapping = {
              "compute": cast_to_compute_host,
              "volume": cast_to_volume_host,
              'network': cast_to_network_host}
  
      func = topic_mapping.get(topic)
      if func:
          func(context, host, method, **kwargs)
      else:
          rpc.cast(context,
                   rpc.queue_get_for(context, topic, host),
                   {"method": method, "args": kwargs})
          LOG.debug(_("Casted '%(method)s' to %(topic)s '%(host)s'")
                  % locals())
  
  
  def encode_instance(instance, local=True):
      """Encode locally created instance for return via RPC"""
      # TODO(comstud): I would love to be able to return the full
      # instance information here, but we'll need some modifications
      # to the RPC code to handle datetime conversions with the
      # json encoding/decoding.  We should be able to set a default
      # json handler somehow to do it.
      #
      # For now, I'll just return the instance ID and let the caller
      # do a DB lookup :-/
      if local:
          return dict(id=instance['id'], _is_precooked=False)
      else:
          inst = dict(instance)
          inst['_is_precooked'] = True
          return inst
  
  
  class Scheduler(object):
      """The base class that all Scheduler classes should inherit from."""
  
      def __init__(self):
          self.host_manager = importutils.import_object(
                  FLAGS.scheduler_host_manager)
          self.compute_api = compute_api.API()
          self.compute_rpcapi = compute_rpcapi.ComputeAPI()
  
      def update_service_capabilities(self, service_name, host, capabilities):
          """Process a capability update from a service node."""
          self.host_manager.update_service_capabilities(service_name,
                  host, capabilities)
  
      def hosts_up(self, context, topic):
          """Return the list of hosts that have a running service for topic."""
  
          services = db.service_get_all_by_topic(context, topic)
          return [service['host']
                  for service in services
                  if utils.service_is_up(service)]
  
      def schedule_prep_resize(self, context, image, request_spec,
                               filter_properties, instance, instance_type,
                               reservations):
          """Must override schedule_prep_resize method for scheduler to work."""
          msg = _("Driver must implement schedule_prep_resize")
          raise NotImplementedError(msg)
  
      def schedule_run_instance(self, context, request_spec,
                                admin_password, injected_files,
                                requested_networks, is_first_time,
                                filter_properties):
          """Must override schedule_run_instance method for scheduler to work."""
          msg = _("Driver must implement schedule_run_instance")
          raise NotImplementedError(msg)
  
      def schedule_create_volume(self, context, volume_id, snapshot_id,
                                 image_id):
          msg = _("Driver must implement schedule_create_volune")
          raise NotImplementedError(msg)
  
      def schedule_live_migration(self, context, instance, dest,
                                  block_migration, disk_over_commit):
          """Live migration scheduling method.
  
          :param context:
          :param instance: instance dict
          :param dest: destination host
          :param block_migration: if true, block_migration.
          :param disk_over_commit: if True, consider real(not virtual)
                                   disk size.
  
          :return:
              The host where instance is running currently.
              Then scheduler send request that host.
          """
          # Check we can do live migration
          self._live_migration_src_check(context, instance)
          self._live_migration_dest_check(context, instance, dest)
          self._live_migration_common_check(context, instance, dest)
          migrate_data = self.compute_rpcapi.check_can_live_migrate_destination(
                  context, instance, dest, block_migration, disk_over_commit)
  
          # Perform migration
          src = instance['host']
          self.compute_rpcapi.live_migration(context, host=src,
                  instance=instance, dest=dest,
                  block_migration=block_migration,
                  migrate_data=migrate_data)
  
      def _live_migration_src_check(self, context, instance_ref):
          """Live migration check routine (for src host).
  
          :param context: security context
          :param instance_ref: nova.db.sqlalchemy.models.Instance object
  
          """
          # TODO(johngar) why is this not in the API layer?
          # Checking instance is running.
          if instance_ref['power_state'] != power_state.RUNNING:
              raise exception.InstanceNotRunning(
                      instance_id=instance_ref['uuid'])
  
          # Checking src host exists and compute node
          src = instance_ref['host']
          try:
              services = db.service_get_all_compute_by_host(context, src)
          except exception.NotFound:
              raise exception.ComputeServiceUnavailable(host=src)
  
          # Checking src host is alive.
          if not utils.service_is_up(services[0]):
              raise exception.ComputeServiceUnavailable(host=src)
  
      def _live_migration_dest_check(self, context, instance_ref, dest):
          """Live migration check routine (for destination host).
  
          :param context: security context
          :param instance_ref: nova.db.sqlalchemy.models.Instance object
          :param dest: destination host
          """
  
          # Checking dest exists and compute node.
          dservice_refs = db.service_get_all_compute_by_host(context, dest)
          dservice_ref = dservice_refs[0]
  
          # Checking dest host is alive.
          if not utils.service_is_up(dservice_ref):
              raise exception.ComputeServiceUnavailable(host=dest)
  
          # Checking whether The host where instance is running
          # and dest is not same.
          src = instance_ref['host']
          if dest == src:
              raise exception.UnableToMigrateToSelf(
                      instance_id=instance_ref['uuid'], host=dest)
  
          # Check memory requirements
          self._assert_compute_node_has_enough_memory(context,
                                                     instance_ref, dest)
  
      def _live_migration_common_check(self, context, instance_ref, dest):
          """Live migration common check routine.
  
          The following checks are based on
          http://wiki.libvirt.org/page/TodoPreMigrationChecks
  
          :param context: security context
          :param instance_ref: nova.db.sqlalchemy.models.Instance object
          :param dest: destination host
          """
          dservice_ref = self._get_compute_info(context, dest)
          src = instance_ref['host']
          oservice_ref = self._get_compute_info(context, src)
  
          # Checking hypervisor is same.
          orig_hypervisor = oservice_ref['hypervisor_type']
          dest_hypervisor = dservice_ref['hypervisor_type']
          if orig_hypervisor != dest_hypervisor:
              raise exception.InvalidHypervisorType()
  
          # Checking hypervisor version.
          orig_hypervisor = oservice_ref['hypervisor_version']
          dest_hypervisor = dservice_ref['hypervisor_version']
          if orig_hypervisor > dest_hypervisor:
              raise exception.DestinationHypervisorTooOld()
  
      def _assert_compute_node_has_enough_memory(self, context,
                                                instance_ref, dest):
          """Checks if destination host has enough memory for live migration.
  
  
          :param context: security context
          :param instance_ref: nova.db.sqlalchemy.models.Instance object
          :param dest: destination host
  
          """
          # Getting total available memory of host
          avail = self._get_compute_info(context, dest)['memory_mb']
  
          # Getting total used memory and disk of host
          # It should be sum of memories that are assigned as max value,
          # because overcommitting is risky.
          instance_refs = db.instance_get_all_by_host(context, dest)
          used = sum([i['memory_mb'] for i in instance_refs])
  
          mem_inst = instance_ref['memory_mb']
          avail = avail - used
          if avail <= mem_inst:
              instance_uuid = instance_ref['uuid']
              reason = _("Unable to migrate %(instance_uuid)s to %(dest)s: "
                         "Lack of memory(host:%(avail)s <= "
                         "instance:%(mem_inst)s)")
              raise exception.MigrationError(reason=reason % locals())
  
      def _get_compute_info(self, context, host):
          """get compute node's information specified by key
  
          :param context: security context
          :param host: hostname(must be compute node)
          :param key: column name of compute_nodes
          :return: value specified by key
  
          """
          compute_node_ref = db.service_get_all_compute_by_host(context, host)
          return compute_node_ref[0]['compute_node'][0]
  