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# Copyright (c) 2010 OpenStack Foundation
# 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 oslo.config import cfg

from nova.compute import utils as compute_utils
from nova.compute import vm_states
from nova.conductor import api as conductor_api
from nova import db
from nova import exception
from nova import notifications
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 timeutils
from nova import servicegroup

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'),
    ]

CONF = cfg.CONF
CONF.register_opts(scheduler_driver_opts)


def handle_schedule_error(context, ex, instance_uuid, request_spec):
    if not isinstance(ex, exception.NoValidHost):
        LOG.exception(_("Exception during scheduler.run_instance"))
    state = vm_states.ERROR.upper()
    LOG.warning(_('Setting instance to %s state.'), state,
                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")
    compute_utils.add_instance_fault_from_exc(context,
            conductor_api.LocalAPI(),
            new_ref, ex, sys.exc_info())

    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 instance_update_db(context, instance_uuid, extra_values=None):
    '''Clear the host and node - set the scheduled_at field of an Instance.

    :returns: An Instance with the updated fields set properly.
    '''
    now = timeutils.utcnow()
    values = {'host': None, 'node': None, 'scheduled_at': now}
    if extra_values:
        values.update(extra_values)

    return db.instance_update(context, instance_uuid, values)


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(
                CONF.scheduler_host_manager)
        self.servicegroup_api = servicegroup.API()

    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 self.servicegroup_api.service_is_up(service)]

    def group_hosts(self, context, group):
        """Return the list of hosts that have VM's from the group."""

        # The system_metadata 'group' will be filtered
        members = db.instance_get_all_by_filters(context,
                {'deleted': False, 'group': group})
        return [member['host']
                for member in members
                if member.get('host') is not None]

    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 select_hosts(self, context, request_spec, filter_properties):
        """Must override select_hosts method for scheduler to work."""
        msg = _("Driver must implement select_hosts")
        raise NotImplementedError(msg)