83 lines
2.5 KiB
Python
83 lines
2.5 KiB
Python
#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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Utilities for handling ISO 8601 duration format.
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"""
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import random
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import re
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import time
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from heat.common.i18n import _
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iso_duration_re = re.compile('PT(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?$')
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wallclock = time.time
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class Duration(object):
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'''
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Note that we don't attempt to handle leap seconds or large clock
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jumps here. The latter are assumed to be rare and the former
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negligible in the context of the timeout. Time zone adjustments,
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Daylight Savings and the like *are* handled. PEP 418 adds a proper
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monotonic clock, but only in Python 3.3.
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'''
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def __init__(self, timeout=0):
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self._endtime = wallclock() + timeout
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def expired(self):
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return wallclock() > self._endtime
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def endtime(self):
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return self._endtime
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def parse_isoduration(duration):
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"""
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Convert duration in ISO 8601 format to second(s).
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Year, Month, Week, and Day designators are not supported.
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Example: 'PT12H30M5S'
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"""
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result = iso_duration_re.match(duration)
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if not result:
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raise ValueError(_('Only ISO 8601 duration format of the form '
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'PT#H#M#S is supported.'))
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t = 0
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t += (3600 * int(result.group(1))) if result.group(1) else 0
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t += (60 * int(result.group(2))) if result.group(2) else 0
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t += int(result.group(3)) if result.group(3) else 0
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return t
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def retry_backoff_delay(attempt, scale_factor=1.0, jitter_max=0.0):
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"""
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Calculate an exponential backoff delay with jitter.
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Delay is calculated as
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2^attempt + (uniform random from [0,1) * jitter_max)
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:param attempt: The count of the current retry attempt
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:param scale_factor: Multiplier to scale the exponential delay by
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:param jitter_max: Maximum of random seconds to add to the delay
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:returns: Seconds since epoch to wait until
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"""
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exp = float(2 ** attempt) * float(scale_factor)
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if jitter_max == 0.0:
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return exp
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return exp + random.random() * jitter_max
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