| Current File : //usr/lib/python2.7/site-packages/vdo/statistics/StatStruct.py |
#
# Copyright (c) 2018 Red Hat, Inc.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.
#
"""
StatStruct -- classes for sampling statistics from a VDO via ioctls
$Id: //eng/vdo-releases/magnesium/src/python/vdo/statistics/StatStruct.py#2 $
"""
from ctypes import *
import collections
import fcntl
import os
import sys
from Field import Field
from LabeledValue import LabeledValue
class Samples(object):
"""
An object which represents a collection of samples from a VDO.
"""
def __init__(self, assays, device, mustBeVDO):
"""
Create a new set of samples by sampling a VDO device.
:param assays: The types of samples to take
:param devices: The device to sample (a dictionary containing
the user-supplied name and the name to use for sampling)
:param mustBeVDO: If set to False, errors resulting from the device not
being a VDO will be suppressed
"""
self.device = device["user"]
self.samples = [assay.sample(os.path.basename(device["sample"]))
for assay in assays]
def getDevice(self):
"""
Get the name of the device which was sampled.
:return: The name of the device
"""
return self.device
def getSamples(self):
"""
Get the list of samples for the device.
:return: The list of samples
"""
return self.samples
@staticmethod
def assay(assays, device, mustBeVDO=True):
"""
Assay a device.
:param assays: The types of samples to take
:param devices: The device to sample (a dictionary containing
the user-supplied name and the name to use for sampling)
:param mustBeVDO: If set to False, errors resulting from the device not
being a VDO will be suppressed
:return: The results of the assays or None if the device is not a VDO and
mustBeVDO is set to False
"""
try:
return Samples(assays, device, mustBeVDO)
except IOError as ioe:
user = device["user"]
if (ioe.errno == 22):
if mustBeVDO:
raise Exception("Device {0} is not a VDO".format(user))
return None
raise Exception("Error sampling device {0}: {1}".format(user, ioe))
@staticmethod
def assayDevices(assays, devices, mustBeVDO=True):
"""
Assay a list of devices.
:param assays: The types of samples to take
:param devices: The devices to sample (a list of dictionaries containing
the user-supplied name and the name to use for sampling)
:param mustBeVDO: If set to False, errors resulting from the device not
being a VDO will be suppressed
:return: The results of the assays or None if the device is not a VDO and
mustBeVDO is set to False
"""
return filter(None, [Samples.assay(assays, device, mustBeVDO)
for device in devices])
@staticmethod
def samplingDevice(user, sample):
"""
Returns a dictionary used for sampling purposes.
The dictionary is structured as:
{ "user" : <user-specified name>,
"sample" : <sample name> }
The user-specified name is used for display purposes.
The sample name is used to perform the actual sampling.
The two names may be identical.
:param user: user-specified name
:param sample: the name to use for sampling
:return: A sampling dictionary.
"""
return { "user" : user, "sample" : sample }
class Sample(object):
"""
An object which represents a single sample (ioctl) of a VDO.
"""
def __init__(self, statStruct, sample):
"""
Create a new sample.
:param statStruct: The structure representing the type of this sample
:param sample: The sampled values
"""
self.statStruct = statStruct
self.sample = sample
def getType(self):
"""
Get the object representing the type of this sample.
:return: The StatStruct which represents the type of this sample
"""
return self.statStruct
def labeled(self):
"""
Get the sampled values as a collection of LabeledValues.
:return: A LabeledValue representing the sampled values
"""
return self.statStruct.labeled(self.sample)
def getStat(self, statName):
"""
Get the value of a named statistic.
:param statName: The name of the statistic, either as a string, or as
a list of strings, one for each level of the sample
hierarchy
:return: The value of the named statistic
"""
if not isinstance(statName, list):
return self.sample[statName]
stats = self.sample
for name in statName[:-1]:
stats = stats[name]
return stats[statName[-1]]
def statEqual(self, other, statName):
"""
Check whether the value of a given statistic is the same in this sample
and some other sample.
:param other: The other sample
:param statName: The name of the statistic as would be specified to
getStat()
:return: True if the value of the named statistic is the same in this and
the other sample
"""
return (self.getStat(statName) == other.getStat(statName))
class StatStruct(Field):
"""
Base class for objects representing a VDO statistics structure. This object
can be used to sample a VDO via an ioctl and convert the result from the
C format in the ioctl to a Sample object.
"""
"""
The dict of C classes
"""
cClasses = {}
def __init__(self, name, fields, **kwargs):
"""
Create a new statistics structure.
:param name: The name of statistics structure
:param fields: A list of Field objects specifying the format of the C
structure returned by the ioctl
:param **kwargs: Keyword args which may be:
labelPrefix: The prefix to prepend to the label for
each field in this structure
ioctl: The value of the ioctl to use for sampling
a VDO
Field: Any of the keyword arguments for the Field
base class
"""
labelPrefix = kwargs.pop('labelPrefix', None)
self.labelPrefix = labelPrefix + ' ' if (labelPrefix != None) else ''
self.ioctl = kwargs.pop('ioctl', None)
self.procFile = kwargs.pop('procFile', None)
self.procRoot = kwargs.pop('procRoot', None)
self.fields = fields
super(StatStruct, self).__init__(name, self._getCClass(), **kwargs)
self.fieldsByName = dict()
for field in fields:
self.fieldsByName[field.name] = field
def _getCClass(self):
"""
Get the Structure class which represents the C struct for a StatStruct
or Field. If the Structure class hasn't yet been made for the given type,
it will be created.
:return: The class defined by the specified set of Fields
"""
className = type(self).__name__ + '.c'
cType = self.cClasses.get(className)
if not cType:
fieldList = [(field.name, field.cType) for field in self.fields
if field.inStruct]
cType = type(className, (Structure,), { '_fields_': fieldList });
self.cClasses[className] = cType
return cType
def sample(self, name):
"""
Get a sample from a VDO via an ioctl.
:param name: The name of the proc directory from which to read
:return: The sample
"""
stats = self.cType()
procPath = os.path.join("/proc", self.procRoot, name, self.procFile)
with open(procPath, 'rb') as fd:
fd.readinto(stats)
return self._extract(stats)
def _extract(self, stats):
"""
Extract the sampled values from the return of an ioctl call.
:param stats: The structure returned from an ioctl
:return: The sample as a Sample
"""
sample = dict()
for field in self.fields:
sample[field.name] = field.extractSample(stats, self)
return Sample(self, sample)
def extractSample(self, stats, parent):
"""
:inherit:
"""
myStats = getattr(stats, self.name, stats)
if (self.length > 1) and (myStats != stats):
# The current field is actually an array, so make a list of the
# extractions of each element of the array.
return [self.extractSample(s, self) for s in myStats]
# The current field is a struct which is not an array, so recursively
# extract each sub-field of that struct
sample = dict()
for field in self.fields:
sample[field.name] = field.extractSample(myStats, self)
return sample
def getSampleValue(self, stats, fieldName):
"""
Get the value of one of the fields at the current level of the C structure
from the ioctl.
:param stats: The current level of the C structure
:param fieldName: The name of the field to get
:return: The value of the specified field
"""
return self.fieldsByName[fieldName].extractSample(stats, self)
def labeled(self, sample, prefix = ''):
"""
:inherit:
"""
prefix += self.labelPrefix
label = prefix + self.label
if isinstance(sample, list):
# The current field is an array, so convert each array element
labeledFields = [self.labeled(s, prefix) for s in sample]
else:
# The current field is a struct, so recursively convert each sub-field
labeledFields = [field.labeled(sample[field.name], prefix)
for field in self.fields if field.display]
return LabeledValue.make(label, labeledFields)