# Copyright 2014 TrilioData Inc.
# All Rights Reserved.

"""
Capacity Weigher.  Weigh hosts by their available capacity.

The default is to spread snapshot operations across all nodes evenly.  If you prefer
stacking, you can set the 'capacity_weight_multiplier' option to a negative
number and the weighing has the opposite effect of the default.
"""

import math

from oslo_config import cfg

from workloadmgr import flags
from workloadmgr.openstack.common.scheduler import weights

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

FLAGS = flags.FLAGS
FLAGS.register_opts(capacity_weight_opts)


class CapacityWeigher(weights.BaseHostWeigher):
    def _weight_multiplier(self):
        """Override the weight multiplier."""
        return FLAGS.capacity_weight_multiplier

    def _weigh_object(self, host_state, weight_properties):
        """Nodes with lower number of outstanding snapshots win.  We want spreading to be the default."""
        running_snapshots = host_state.running_snapshots
        return running_snapshots