154 lines
4.3 KiB
Python
154 lines
4.3 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2015 Yahoo! Inc. All Rights Reserved.
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#
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# All Rights Reserved.
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#
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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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import logging
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import os
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import time
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# log level for low-level debugging
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BLATHER = 5
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LOG = logging.getLogger(__name__)
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def canonicalize_path(path):
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"""Canonicalizes a potential path.
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Returns a binary string encoded into filesystem encoding.
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"""
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if isinstance(path, bytes):
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return path
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if isinstance(path, str):
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return os.fsencode(path)
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else:
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return canonicalize_path(str(path))
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def pick_first_not_none(*values):
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"""Returns first of values that is *not* None (or None if all are/were)."""
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for val in values:
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if val is not None:
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return val
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return None
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class LockStack(object):
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"""Simple lock stack to get and release many locks.
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An instance of this should **not** be used by many threads at the
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same time, as the stack that is maintained will be corrupted and
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invalid if that is attempted.
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"""
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def __init__(self, logger=None):
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self._stack = []
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self._logger = pick_first_not_none(logger, LOG)
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def acquire_lock(self, lock):
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gotten = lock.acquire()
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if gotten:
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self._stack.append(lock)
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return gotten
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def __enter__(self):
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return self
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def __exit__(self, exc_type, exc_value, exc_tb):
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am_left = len(self._stack)
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tot_am = am_left
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while self._stack:
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lock = self._stack.pop()
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try:
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lock.release()
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except Exception:
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self._logger.exception("Failed releasing lock %s from lock"
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" stack with %s locks", am_left, tot_am)
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am_left -= 1
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class RetryAgain(Exception):
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"""Exception to signal to retry helper to try again."""
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class Retry(object):
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"""A little retry helper object."""
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def __init__(self, delay, max_delay,
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sleep_func=time.sleep, watch=None):
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self.delay = delay
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self.attempts = 0
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self.max_delay = max_delay
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self.sleep_func = sleep_func
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self.watch = watch
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def __call__(self, fn, *args, **kwargs):
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while True:
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self.attempts += 1
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try:
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return fn(*args, **kwargs)
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except RetryAgain:
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maybe_delay = self.attempts * self.delay
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if maybe_delay < self.max_delay:
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actual_delay = maybe_delay
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else:
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actual_delay = self.max_delay
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actual_delay = max(0.0, actual_delay)
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if self.watch is not None:
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leftover = self.watch.leftover()
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if leftover is not None and leftover < actual_delay:
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actual_delay = leftover
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self.sleep_func(actual_delay)
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class StopWatch(object):
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"""A really basic stop watch."""
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def __init__(self, duration=None):
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self.duration = duration
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self.started_at = None
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self.stopped_at = None
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def leftover(self):
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if self.duration is None:
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return None
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return max(0.0, self.duration - self.elapsed())
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def elapsed(self):
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if self.stopped_at is not None:
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end_time = self.stopped_at
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else:
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end_time = time.monotonic()
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return max(0.0, end_time - self.started_at)
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def __enter__(self):
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self.start()
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return self
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def __exit__(self, exc_type, exc_value, exc_tb):
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self.stopped_at = time.monotonic()
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def start(self):
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self.started_at = time.monotonic()
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self.stopped_at = None
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def expired(self):
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if self.duration is None:
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return False
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else:
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return self.elapsed() > self.duration
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