deb-horizon/horizon/utils/units.py
Doug Fish 4f15492980 Update metering unit selection to use smaller units for time
Update the unit selection to not convert to a higher unit until
the max value is at least 2 units.

Change-Id: I349b328b553ed634a70b70b695d4db92295c9b67
Closes-bug: #1384248
2014-11-19 20:44:43 -06:00

148 lines
4.3 KiB
Python

# 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 decimal
import pint
from horizon.utils import functions
# Mapping of units from Ceilometer to Pint
INFORMATION_UNITS = (
('B', 'byte'),
('KB', 'Kibyte'),
('MB', 'Mibyte'),
('GB', 'Gibyte'),
('TB', 'Tibyte'),
('PB', 'Pibyte'),
('EB', 'Eibyte'),
)
TIME_UNITS = ('ns', 's', 'min', 'hr', 'day', 'week', 'month', 'year')
ureg = pint.UnitRegistry()
def is_supported(unit):
"""Returns a bool indicating whether the unit specified is supported by
this module.
"""
return unit in functions.get_keys(INFORMATION_UNITS) + TIME_UNITS
def is_larger(unit_1, unit_2):
"""Returns a boolean indicating whether unit_1 is larger than unit_2.
E.g:
>>> is_larger('KB', 'B')
True
>>> is_larger('min', 'day')
False
"""
unit_1 = functions.value_for_key(INFORMATION_UNITS, unit_1)
unit_2 = functions.value_for_key(INFORMATION_UNITS, unit_2)
return ureg.parse_expression(unit_1) > ureg.parse_expression(unit_2)
def convert(value, source_unit, target_unit, fmt=False):
"""Converts value from source_unit to target_unit. Returns a tuple
containing the converted value and target_unit. Having fmt set to True
causes the value to be formatted to 1 decimal digit if it's a decimal or
be formatted as integer if it's an integer.
E.g:
>>> convert(2, 'hr', 'min')
(120.0, 'min')
>>> convert(2, 'hr', 'min', fmt=True)
(120, 'min')
>>> convert(30, 'min', 'hr', fmt=True)
(0.5, 'hr')
"""
orig_target_unit = target_unit
source_unit = functions.value_for_key(INFORMATION_UNITS, source_unit)
target_unit = functions.value_for_key(INFORMATION_UNITS, target_unit)
q = ureg.Quantity(value, source_unit)
q = q.to(ureg.parse_expression(target_unit))
value = functions.format_value(q.magnitude) if fmt else q.magnitude
return value, orig_target_unit
def normalize(value, unit):
"""Converts the value so that it belongs to some expected range.
Returns the new value and new unit.
E.g:
>>> normalize(1024, 'KB')
(1, 'MB')
>>> normalize(90, 'min')
(1.5, 'hr')
>>> normalize(1.0, 'object')
(1, 'object')
"""
if value < 0:
raise ValueError('Negative value: %s %s.' % (value, unit))
if unit in functions.get_keys(INFORMATION_UNITS):
return _normalize_information(value, unit)
elif unit in TIME_UNITS:
return _normalize_time(value, unit)
else:
# Unknown unit, just return it
return functions.format_value(value), unit
def _normalize_information(value, unit):
value = decimal.Decimal(str(value))
while value < 1:
prev_unit = functions.previous_key(INFORMATION_UNITS, unit)
if prev_unit is None:
break
value, unit = convert(value, unit, prev_unit)
while value >= 1024:
next_unit = functions.next_key(INFORMATION_UNITS, unit)
if next_unit is None:
break
value, unit = convert(value, unit, next_unit)
return functions.format_value(value), unit
def _normalize_time(value, unit):
# Normalize time by converting to next higher unit when value is
# at least 2 units
value, unit = convert(value, unit, 's')
if value >= 120:
value, unit = convert(value, 's', 'min')
if value >= 120:
value, unit = convert(value, 'min', 'hr')
if value >= 48:
value, unit = convert(value, 'hr', 'day')
if value >= 730:
value, unit = convert(value, 'day', 'year')
elif value >= 62:
value, unit = convert(value, 'day', 'month')
elif value >= 14:
value, unit = convert(value, 'day', 'week')
return functions.format_value(value), unit