# Copyright (c) 2014 OpenStack Foundation
# 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
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"""
Weighers that weigh hosts by volume number in backends:

1. Volume Number Weigher.  Weigh hosts by their volume number.

The default is to spread volumes across all hosts evenly.  If you prefer
stacking, you can set the 'volume_number_multiplier' option to a positive
number and the weighing has the opposite effect of the default.
"""


from oslo.config import cfg

from cinder import db
from cinder.openstack.common import log as logging
from cinder.openstack.common.scheduler import weights


LOG = logging.getLogger(__name__)


volume_number_weight_opts = [
    cfg.FloatOpt('volume_number_multiplier',
                 default=-1.0,
                 help='Multiplier used for weighing volume number. '
                      'Negative numbers mean to spread vs stack.'),
]

CONF = cfg.CONF
CONF.register_opts(volume_number_weight_opts)


class VolumeNumberWeigher(weights.BaseHostWeigher):
    def _weight_multiplier(self):
        """Override the weight multiplier."""
        return CONF.volume_number_multiplier

    def _weigh_object(self, host_state, weight_properties):
        """Less volume number weights win.
        We want spreading to be the default.
        """
        context = weight_properties['context']
        volume_number = db.volume_data_get_for_host(context=context,
                                                    host=host_state.host,
                                                    count_only=True)
        return volume_number
