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# Copyright (c) 2011 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
# 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.
Metrics Weigher. Weigh hosts by their metrics.
This weigher can compute the weight based on the compute node host's various
metrics. The to-be weighed metrics and their weighing ratio are specified
in the configuration file as the followings:
weight_setting = name1=1.0, name2=-1.0
The final weight would be name1.value * 1.0 + name2.value * -1.0.
import nova.conf
from nova import exception
from nova.scheduler import utils
from nova.scheduler import weights
CONF = nova.conf.CONF
class MetricsWeigher(weights.BaseHostWeigher):
def __init__(self):
def _parse_setting(self):
self.setting = utils.parse_options(CONF.metrics.weight_setting,
def weight_multiplier(self, host_state):
"""Override the weight multiplier."""
return utils.get_weight_multiplier(
host_state, 'metrics_weight_multiplier',
def _weigh_object(self, host_state, weight_properties):
value = 0.0
# NOTE(sbauza): Keying a dict of Metrics per metric name given that we
# have a MonitorMetricList object
metrics_dict = { m for m in host_state.metrics or []}
for (name, ratio) in self.setting:
value += metrics_dict[name].value * ratio
except KeyError:
if CONF.metrics.required:
raise exception.ComputeHostMetricNotFound(,
# We treat the unavailable metric as the most negative
# factor, i.e. set the value to make this obj would be
# at the end of the ordered weighed obj list
# Do nothing if ratio or weight_multiplier is 0.
if ratio * self.weight_multiplier(host_state) != 0:
return CONF.metrics.weight_of_unavailable
return value