OpenStack Orchestration (Heat)
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# 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
# 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.
"""Utilities for handling ISO 8601 duration format."""
import random
import re
import time
from heat.common.i18n import _
iso_duration_re = re.compile(r'PT(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?$')
wallclock = time.time
class Duration(object):
# (NOTE): we don't attempt to handle leap seconds or large clock
# jumps here. The latter are assumed to be rare and the former
# negligible in the context of the timeout. Time zone adjustments,
# Daylight Savings and the like *are* handled. PEP 418 adds a proper
# monotonic clock, but only in Python 3.3.
def __init__(self, timeout=0):
self._endtime = wallclock() + timeout
def expired(self):
return wallclock() > self._endtime
def endtime(self):
return self._endtime
def parse_isoduration(duration):
"""Convert duration in ISO 8601 format to second(s).
Year, Month, Week, and Day designators are not supported.
Example: 'PT12H30M5S'
result = iso_duration_re.match(duration)
if not result:
raise ValueError(_('Only ISO 8601 duration format of the form '
'PT#H#M#S is supported.'))
t = 0
t += (3600 * int( if else 0
t += (60 * int( if else 0
t += int( if else 0
return t
def retry_backoff_delay(attempt, scale_factor=1.0, jitter_max=0.0):
"""Calculate an exponential backoff delay with jitter.
Delay is calculated as
2^attempt + (uniform random from [0,1) * jitter_max)
:param attempt: The count of the current retry attempt
:param scale_factor: Multiplier to scale the exponential delay by
:param jitter_max: Maximum of random seconds to add to the delay
:returns: Seconds since epoch to wait until
exp = float(2 ** attempt) * float(scale_factor)
if jitter_max == 0.0:
return exp
return exp + random.random() * jitter_max
def isotime(at):
"""Stringify UTC time in ISO 8601 format.
:param at: Timestamp in UTC to format.
if at is None:
return None
return at.strftime('%Y-%m-%dT%H:%M:%SZ')