7fe05a8ca4
This patch addresses a problem in which the current Nova metrics can
yield a set of incoherent results. For example, prior to this patch,
it is possible that a collection of metrics sent in a single RPC
notification message can contain values such as the following:
{'cpu.user.percent': A, 'cpu.kernel.percent': B,
'cpu.idle.percent': C, 'cpu.iowait.percent': D} such that you can
end up with A + B + C + D != 100, which does not make any sense
from an end consumer perspective.
The root cause of this problem stems from the fact that each
individual metric retrieval (i.e., via get_metric(name)) could
result in the driver.get_host_cpu_stats() function being called,
which leads to the incoherent results mentioned above.
To solve this, we only refresh the metric data once per collection
cycle. Additionally, the `Monitor` base class uses get_metrics()
instead of get_metric() and returns a 3-tuple of the form
(metric_name, metric_value, timestamp).
This patch also removes some code from the CPU virt_driver's
_update_data() method that checked whether the last call was
less than 1 second ago, which seemed to try to solve this
coherency issue, but didn't really work all of the time (and hence
how this defect was encountered to begin with). Given we use the
[more appropriate] metric set approach now, this code no longer
serves any purpose.
Unit tests updated to work with the new framework.
Change-Id: Ia23783f2e6b92b3af2e9acf09f95a9eeacd8eb3b
Closes-Bug: 1490837
Co-authored-by: Jay Pipes <jaypipes@gmail.com>
95 lines
3.5 KiB
Python
95 lines
3.5 KiB
Python
# 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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import abc
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import six
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from nova import objects
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from nova.objects import fields
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@six.add_metaclass(abc.ABCMeta)
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class MonitorBase(object):
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"""Base class for all resource monitor plugins.
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A monitor is responsible for adding a set of related metrics to
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a `nova.objects.MonitorMetricList` object after the monitor has
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performed some sampling or monitoring action.
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"""
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def __init__(self, compute_manager):
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self.compute_manager = compute_manager
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self.source = None
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@abc.abstractmethod
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def get_metric_names(self):
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"""Get available metric names.
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Get available metric names, which are represented by a set of keys
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that can be used to check conflicts and duplications
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:returns: set containing one or more values from
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:py:attr: nova.objects.fields.MonitorMetricType.ALL
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"""
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raise NotImplementedError('get_metric_names')
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@abc.abstractmethod
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def get_metrics(self):
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"""Returns a list of tuples containing information for all metrics
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tracked by the monitor.
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Note that if the monitor class is responsible for tracking a *related*
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set of metrics -- e.g. a set of percentages of CPU time allocated to
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user, kernel, and idle -- it is the responsibility of the monitor
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implementation to do a single sampling call to the underlying monitor
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to ensure that related metric values make logical sense.
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:returns: list of (metric_name, value, timestamp) tuples
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"""
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raise NotImplementedError('get_metrics')
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def add_metrics_to_list(self, metrics_list):
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"""Adds metric objects to a supplied list object.
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:param metric_list: nova.objects.MonitorMetricList that the monitor
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plugin should append nova.objects.MonitorMetric
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objects to.
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"""
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metric_data = self.get_metrics()
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metrics = []
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for (name, value, timestamp) in metric_data:
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metric = objects.MonitorMetric(name=name,
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value=value,
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timestamp=timestamp,
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source=self.source)
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metrics.append(metric)
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metrics_list.objects.extend(metrics)
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class CPUMonitorBase(MonitorBase):
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"""Base class for all monitors that return CPU-related metrics."""
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def get_metric_names(self):
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return set([
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fields.MonitorMetricType.CPU_FREQUENCY,
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fields.MonitorMetricType.CPU_USER_TIME,
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fields.MonitorMetricType.CPU_KERNEL_TIME,
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fields.MonitorMetricType.CPU_IDLE_TIME,
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fields.MonitorMetricType.CPU_IOWAIT_TIME,
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fields.MonitorMetricType.CPU_USER_PERCENT,
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fields.MonitorMetricType.CPU_KERNEL_PERCENT,
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fields.MonitorMetricType.CPU_IDLE_PERCENT,
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fields.MonitorMetricType.CPU_IOWAIT_PERCENT,
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fields.MonitorMetricType.CPU_PERCENT,
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])
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