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 _scale(self, s):
"""Apply the scaling factor.
Either a straight multiplicative factor or else a string to be eval'd.
"""
ns = transformer.Namespace(s.as_dict())
scale = self.scale
return ((eval(scale, {}, ns) if isinstance(scale, six.string_types)
else s.volume * scale) if scale else s.volume)
