OpenStack Study: metrics.py

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# 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.

"""

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:

[metrics]

weight_setting = name1=1.0, name2=-1.0

The final weight would be name1.value * 1.0 + name2.value * -1.0.

"""

from oslo.config import cfg

from nova import exception

from nova.scheduler import utils

from nova.scheduler import weights

metrics_weight_opts = [

cfg.FloatOpt('weight_multiplier',

default=1.0,

help='Multiplier used for weighing metrics.'),

cfg.ListOpt('weight_setting',

default=[],

help='How the metrics are going to be weighed. This '

'should be in the form of "=, '

'=, ...", where is one '

'of the metrics to be weighed, and is '

'the corresponding ratio. So for "name1=1.0, '

'name2=-1.0" The final weight would be '

'name1.value * 1.0 + name2.value * -1.0.'),

cfg.BoolOpt('required',

default=True,

help='How to treat the unavailable metrics. When a '

'metric is NOT available for a host, if it is set '

'to be True, it would raise an exception, so it '

'is recommended to use the scheduler filter '

'MetricFilter to filter out those hosts. If it is '

'set to be False, the unavailable metric would be '

'treated as a negative factor in weighing '

'process, the returned value would be set by '

'the option weight_of_unavailable.'),

cfg.FloatOpt('weight_of_unavailable',

default=float(-10000.0),

help='The final weight value to be returned if '

'required is set to False and any one of the '

'metrics set by weight_setting is unavailable.'),

]

CONF = cfg.CONF

CONF.register_opts(metrics_weight_opts, group='metrics')

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class MetricsWeigher(weights.BaseHostWeigher):

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def __init__(self):

self._parse_setting()

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def _parse_setting(self):

self.setting = utils.parse_options(CONF.metrics.weight_setting,

sep='=',

converter=float,

name="metrics.weight_setting")

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def weight_multiplier(self):

"""Override the weight multiplier."""

return CONF.metrics.weight_multiplier

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def _weigh_object(self, host_state, weight_properties):

value = 0.0

for (name, ratio) in self.setting:

try:

value += host_state.metrics[name].value * ratio

except KeyError:

if CONF.metrics.required:

raise exception.ComputeHostMetricNotFound(

host=host_state.host,

node=host_state.nodename,

name=name)

else:

# 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() != 0:

return CONF.metrics.weight_of_unavailable

return value