deb-ceilometer/ceilometer/transformer/arithmetic.py

156 lines
5.9 KiB
Python

#
# Copyright 2014 Red Hat, Inc
#
# 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.
import collections
import keyword
import math
import re
from oslo_log import log
import six
from ceilometer.i18n import _
from ceilometer import sample
from ceilometer import transformer
LOG = log.getLogger(__name__)
class ArithmeticTransformer(transformer.TransformerBase):
"""Multi meter arithmetic transformer.
Transformer that performs arithmetic operations
over one or more meters and/or their metadata.
"""
meter_name_re = re.compile(r'\$\(([\w\.\-]+)\)')
def __init__(self, target=None, **kwargs):
super(ArithmeticTransformer, self).__init__(**kwargs)
target = target or {}
self.target = target
self.expr = target.get('expr', '')
self.expr_escaped, self.escaped_names = self.parse_expr(self.expr)
self.required_meters = list(self.escaped_names.values())
self.misconfigured = len(self.required_meters) == 0
if not self.misconfigured:
self.reference_meter = self.required_meters[0]
# convert to set for more efficient contains operation
self.required_meters = set(self.required_meters)
self.cache = collections.defaultdict(dict)
self.latest_timestamp = None
else:
LOG.warn(_('Arithmetic transformer must use at least one'
' meter in expression \'%s\''), self.expr)
def _update_cache(self, _sample):
"""Update the cache with the latest sample."""
escaped_name = self.escaped_names.get(_sample.name, '')
if escaped_name not in self.required_meters:
return
self.cache[_sample.resource_id][escaped_name] = _sample
def _check_requirements(self, resource_id):
"""Check if all the required meters are available in the cache."""
return len(self.cache[resource_id]) == len(self.required_meters)
def _calculate(self, resource_id):
"""Evaluate the expression and return a new sample if successful."""
ns_dict = dict((m, s.as_dict()) for m, s
in six.iteritems(self.cache[resource_id]))
ns = transformer.Namespace(ns_dict)
try:
new_volume = eval(self.expr_escaped, {}, ns)
if math.isnan(new_volume):
raise ArithmeticError(_('Expression evaluated to '
'a NaN value!'))
reference_sample = self.cache[resource_id][self.reference_meter]
return sample.Sample(
name=self.target.get('name', reference_sample.name),
unit=self.target.get('unit', reference_sample.unit),
type=self.target.get('type', reference_sample.type),
volume=float(new_volume),
user_id=reference_sample.user_id,
project_id=reference_sample.project_id,
resource_id=reference_sample.resource_id,
timestamp=self.latest_timestamp,
resource_metadata=reference_sample.resource_metadata
)
except Exception as e:
LOG.warn(_('Unable to evaluate expression %(expr)s: %(exc)s'),
{'expr': self.expr, 'exc': e})
def handle_sample(self, context, _sample):
self._update_cache(_sample)
self.latest_timestamp = _sample.timestamp
def flush(self, context):
new_samples = []
if not self.misconfigured:
for resource_id in self.cache:
if self._check_requirements(resource_id):
new_samples.append(self._calculate(resource_id))
else:
LOG.warn(_('Unable to perform calculation, not all of '
'{%s} are present'),
', '.join(self.required_meters))
self.cache.clear()
return new_samples
@classmethod
def parse_expr(cls, expr):
"""Transforms meter names in the expression into valid identifiers.
:param expr: unescaped expression
:return: A tuple of the escaped expression and a dict representing
the translation of meter names into Python identifiers
"""
class Replacer(object):
"""Replaces matched meter names with escaped names.
If the meter name is not followed by parameter access in the
expression, it defaults to accessing the 'volume' parameter.
"""
def __init__(self, original_expr):
self.original_expr = original_expr
self.escaped_map = {}
def __call__(self, match):
meter_name = match.group(1)
escaped_name = self.escape(meter_name)
self.escaped_map[meter_name] = escaped_name
if (match.end(0) == len(self.original_expr) or
self.original_expr[match.end(0)] != '.'):
escaped_name += '.volume'
return escaped_name
@staticmethod
def escape(name):
has_dot = '.' in name
if has_dot:
name = name.replace('.', '_')
if has_dot or name.endswith('ESC') or name in keyword.kwlist:
name = "_" + name + '_ESC'
return name
replacer = Replacer(expr)
expr = re.sub(cls.meter_name_re, replacer, expr)
return expr, replacer.escaped_map