| ## 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) |
