72 lines
2.3 KiB
Python
72 lines
2.3 KiB
Python
# Copyright (c) 2011-2012 OpenStack Foundation
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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Pluggable Weighing support
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"""
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from nova import loadables
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class WeighedObject(object):
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"""Object with weight information."""
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def __init__(self, obj, weight):
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self.obj = obj
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self.weight = weight
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def __repr__(self):
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return "<WeighedObject '%s': %s>" % (self.obj, self.weight)
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class BaseWeigher(object):
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"""Base class for pluggable weighers."""
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def _weight_multiplier(self):
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"""How weighted this weigher should be. Normally this would
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be overridden in a subclass based on a config value.
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"""
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return 1.0
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def _weigh_object(self, obj, weight_properties):
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"""Override in a subclass to specify a weight for a specific
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object.
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"""
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return 0.0
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def weigh_objects(self, weighed_obj_list, weight_properties):
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"""Weigh multiple objects. Override in a subclass if you need
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need access to all objects in order to manipulate weights.
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"""
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for obj in weighed_obj_list:
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obj.weight += (self._weight_multiplier() *
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self._weigh_object(obj.obj, weight_properties))
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class BaseWeightHandler(loadables.BaseLoader):
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object_class = WeighedObject
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def get_weighed_objects(self, weigher_classes, obj_list,
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weighing_properties):
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"""Return a sorted (highest score first) list of WeighedObjects."""
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if not obj_list:
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return []
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weighed_objs = [self.object_class(obj, 0.0) for obj in obj_list]
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for weigher_cls in weigher_classes:
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weigher = weigher_cls()
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weigher.weigh_objects(weighed_objs, weighing_properties)
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return sorted(weighed_objs, key=lambda x: x.weight, reverse=True)
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