Edit: retrying.py
## Copyright 2013-2014 Ray Holder ## ## 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 random from pip._vendor import six import sys import time import traceback # sys.maxint / 2, since Python 3.2 doesn't have a sys.maxint... MAX_WAIT = 1073741823 def retry(*dargs, **dkw): """ Decorator function that instantiates the Retrying object @param *dargs: positional arguments passed to Retrying object @param **dkw: keyword arguments passed to the Retrying object """ # support both @retry and @retry() as valid syntax if len(dargs) == 1 and callable(dargs[0]): def wrap_simple(f): @six.wraps(f) def wrapped_f(*args, **kw): return Retrying().call(f, *args, **kw) return wrapped_f return wrap_simple(dargs[0]) else: def wrap(f): @six.wraps(f) def wrapped_f(*args, **kw): return Retrying(*dargs, **dkw).call(f, *args, **kw) return wrapped_f return wrap class Retrying(object): def __init__(self, stop=None, wait=None, stop_max_attempt_number=None, stop_max_delay=None, wait_fixed=None, wait_random_min=None, wait_random_max=None, wait_incrementing_start=None, wait_incrementing_increment=None, wait_exponential_multiplier=None, wait_exponential_max=None, retry_on_exception=None, retry_on_result=None, wrap_exception=False, stop_func=None, wait_func=None, wait_jitter_max=None): self._stop_max_attempt_number = 5 if stop_max_attempt_number is None else stop_max_attempt_number self._stop_max_delay = 100 if stop_max_delay is None else stop_max_delay self._wait_fixed = 1000 if wait_fixed is None else wait_fixed self._wait_random_min = 0 if wait_random_min is None else wait_random_min self._wait_random_max = 1000 if wait_random_max is None else wait_random_max self._wait_incrementing_start = 0 if wait_incrementing_start is None else wait_incrementing_start self._wait_incrementing_increment = 100 if wait_incrementing_increment is None else wait_incrementing_increment self._wait_exponential_multiplier = 1 if wait_exponential_multiplier is None else wait_exponential_multiplier self._wait_exponential_max = MAX_WAIT if wait_exponential_max is None else wait_exponential_max self._wait_jitter_max = 0 if wait_jitter_max is None else wait_jitter_max # TODO add chaining of stop behaviors # stop behavior stop_funcs = [] if stop_max_attempt_number is not None: stop_funcs.append(self.stop_after_attempt) if stop_max_delay is not None: stop_funcs.append(self.stop_after_delay) if stop_func is not None: self.stop = stop_func elif stop is None: self.stop = lambda attempts, delay: any(f(attempts, delay) for f in stop_funcs) else: self.stop = getattr(self, stop) # TODO add chaining of wait behaviors # wait behavior wait_funcs = [lambda *args, **kwargs: 0] if wait_fixed is not None: wait_funcs.append(self.fixed_sleep) if wait_random_min is not None or wait_random_max is not None: wait_funcs.append(self.random_sleep) if wait_incrementing_start is not None or wait_incrementing_increment is not None: wait_funcs.append(self.incrementing_sleep) if wait_exponential_multiplier is not None or wait_exponential_max is not None: wait_funcs.append(self.exponential_sleep) if wait_func is not None: self.wait = wait_func elif wait is None: self.wait = lambda attempts, delay: max(f(attempts, delay) for f in wait_funcs) else: self.wait = getattr(self, wait) # retry on exception filter if retry_on_exception is None: self._retry_on_exception = self.always_reject else: self._retry_on_exception = retry_on_exception # TODO simplify retrying by Exception types # retry on result filter if retry_on_result is None: self._retry_on_result = self.never_reject else: self._retry_on_result = retry_on_result self._wrap_exception = wrap_exception def stop_after_attempt(self, previous_attempt_number, delay_since_first_attempt_ms): """Stop after the previous attempt >= stop_max_attempt_number.""" return previous_attempt_number >= self._stop_max_attempt_number def stop_after_delay(self, previous_attempt_number, delay_since_first_attempt_ms): """Stop after the time from the first attempt >= stop_max_delay.""" return delay_since_first_attempt_ms >= self._stop_max_delay def no_sleep(self, previous_attempt_number, delay_since_first_attempt_ms): """Don't sleep at all before retrying.""" return 0 def fixed_sleep(self, previous_attempt_number, delay_since_first_attempt_ms): """Sleep a fixed amount of time between each retry.""" return self._wait_fixed def random_sleep(self, previous_attempt_number, delay_since_first_attempt_ms): """Sleep a random amount of time between wait_random_min and wait_random_max""" return random.randint(self._wait_random_min, self._wait_random_max) def incrementing_sleep(self, previous_attempt_number, delay_since_first_attempt_ms): """ Sleep an incremental amount of time after each attempt, starting at wait_incrementing_start and incrementing by wait_incrementing_increment """ result = self._wait_incrementing_start + (self._wait_incrementing_increment * (previous_attempt_number - 1)) if result < 0: result = 0 return result def exponential_sleep(self, previous_attempt_number, delay_since_first_attempt_ms): exp = 2 ** previous_attempt_number result = self._wait_exponential_multiplier * exp if result > self._wait_exponential_max: result = self._wait_exponential_max if result < 0: result = 0 return result def never_reject(self, result): return False def always_reject(self, result): return True def should_reject(self, attempt): reject = False if attempt.has_exception: reject |= self._retry_on_exception(attempt.value[1]) else: reject |= self._retry_on_result(attempt.value) return reject def call(self, fn, *args, **kwargs): start_time = int(round(time.time() * 1000)) attempt_number = 1 while True: try: attempt = Attempt(fn(*args, **kwargs), attempt_number, False) except: tb = sys.exc_info() attempt = Attempt(tb, attempt_number, True) if not self.should_reject(attempt): return attempt.get(self._wrap_exception) delay_since_first_attempt_ms = int(round(time.time() * 1000)) - start_time if self.stop(attempt_number, delay_since_first_attempt_ms): if not self._wrap_exception and attempt.has_exception: # get() on an attempt with an exception should cause it to be raised, but raise just in case raise attempt.get() else: raise RetryError(attempt) else: sleep = self.wait(attempt_number, delay_since_first_attempt_ms) if self._wait_jitter_max: jitter = random.random() * self._wait_jitter_max sleep = sleep + max(0, jitter) time.sleep(sleep / 1000.0) attempt_number += 1 class Attempt(object): """ An Attempt encapsulates a call to a target function that may end as a normal return value from the function or an Exception depending on what occurred during the execution. """ def __init__(self, value, attempt_number, has_exception): self.value = value self.attempt_number = attempt_number self.has_exception = has_exception def get(self, wrap_exception=False): """ Return the return value of this Attempt instance or raise an Exception. If wrap_exception is true, this Attempt is wrapped inside of a RetryError before being raised. """ if self.has_exception: if wrap_exception: raise RetryError(self) else: six.reraise(self.value[0], self.value[1], self.value[2]) else: return self.value def __repr__(self): if self.has_exception: return "Attempts: {0}, Error:\n{1}".format(self.attempt_number, "".join(traceback.format_tb(self.value[2]))) else: return "Attempts: {0}, Value: {1}".format(self.attempt_number, self.value) class RetryError(Exception): """ A RetryError encapsulates the last Attempt instance right before giving up. """ def __init__(self, last_attempt): self.last_attempt = last_attempt def __str__(self): return "RetryError[{0}]".format(self.last_attempt)
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