88 lines
3.4 KiB
Python
88 lines
3.4 KiB
Python
# Copyright 2012 Anton Beloglazov
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain 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,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Trivial underload detection algorithms.
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"""
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def always_underloaded_factory(time_step, migration_time, params):
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"""Creates an algorithm that always considers the host underloaded.
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:param time_step: The length of the simulation time step in seconds.
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:param migration_time: The VM migration time in time seconds.
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:param params: A dictionary containing the algorithm's parameters.
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:return: A function implementing the algorithm.
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"""
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return lambda utilization, state=None: (True, {})
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def threshold_factory(time_step, migration_time, params):
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"""Creates the threshold underload detection algorithm.
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:param time_step: The length of the simulation time step in seconds.
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:param migration_time: The VM migration time in time seconds.
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:param params: A dictionary containing the algorithm's parameters.
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:return: A function implementing the OTF algorithm.
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"""
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return lambda utilization, state=None: (threshold(params['threshold'],
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utilization),
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{})
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def last_n_average_threshold_factory(time_step, migration_time, params):
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"""Creates the averaging threshold underload detection algorithm.
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:param time_step: The length of the simulation time step in seconds.
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:param migration_time: The VM migration time in time seconds.
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:param params: A dictionary containing the algorithm's parameters.
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:return: A function implementing the averaging underload detection.
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"""
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return lambda utilization, state=None: (
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last_n_average_threshold(params['threshold'],
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params['n'],
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utilization),
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{})
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def threshold(threshold, utilization):
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"""Static threshold-based underload detection algorithm.
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The algorithm returns True, if the last value of the host's
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CPU utilization is lower than the specified threshold.
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:param threshold: The static underload CPU utilization threshold.
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:param utilization: The history of the host's CPU utilization.
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:return: A decision of whether the host is underloaded.
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"""
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if utilization:
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return utilization[-1] <= threshold
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return False
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def last_n_average_threshold(threshold, n, utilization):
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"""Averaging static threshold-based underload detection algorithm.
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The algorithm returns True, if the average of the last n values of
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the host's CPU utilization is lower than the specified threshold.
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:param threshold: The static underload CPU utilization threshold.
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:param n: The number of last values to average.
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:param utilization: The history of the host's CPU utilization.
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:return: A decision of whether the host is underloaded.
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"""
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if utilization:
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utilization = utilization[-n:]
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return sum(utilization) / len(utilization) <= threshold
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return False
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