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267 lines
9.7 KiB
267 lines
9.7 KiB
## Copyright 2013-2014 Ray Holder
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##
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## Licensed under the Apache License, Version 2.0 (the "License");
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## you may not use this file except in compliance with the License.
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## You may obtain 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,
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## WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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## See the License for the specific language governing permissions and
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## limitations under the License.
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import random
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import six
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import sys
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import time
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import traceback
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# sys.maxint / 2, since Python 3.2 doesn't have a sys.maxint...
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MAX_WAIT = 1073741823
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def retry(*dargs, **dkw):
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"""
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Decorator function that instantiates the Retrying object
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@param *dargs: positional arguments passed to Retrying object
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@param **dkw: keyword arguments passed to the Retrying object
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"""
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# support both @retry and @retry() as valid syntax
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if len(dargs) == 1 and callable(dargs[0]):
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def wrap_simple(f):
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@six.wraps(f)
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def wrapped_f(*args, **kw):
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return Retrying().call(f, *args, **kw)
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return wrapped_f
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return wrap_simple(dargs[0])
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else:
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def wrap(f):
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@six.wraps(f)
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def wrapped_f(*args, **kw):
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return Retrying(*dargs, **dkw).call(f, *args, **kw)
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return wrapped_f
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return wrap
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class Retrying(object):
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def __init__(self,
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stop=None, wait=None,
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stop_max_attempt_number=None,
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stop_max_delay=None,
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wait_fixed=None,
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wait_random_min=None, wait_random_max=None,
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wait_incrementing_start=None, wait_incrementing_increment=None,
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wait_exponential_multiplier=None, wait_exponential_max=None,
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retry_on_exception=None,
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retry_on_result=None,
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wrap_exception=False,
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stop_func=None,
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wait_func=None,
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wait_jitter_max=None):
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self._stop_max_attempt_number = 5 if stop_max_attempt_number is None else stop_max_attempt_number
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self._stop_max_delay = 100 if stop_max_delay is None else stop_max_delay
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self._wait_fixed = 1000 if wait_fixed is None else wait_fixed
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self._wait_random_min = 0 if wait_random_min is None else wait_random_min
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self._wait_random_max = 1000 if wait_random_max is None else wait_random_max
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self._wait_incrementing_start = 0 if wait_incrementing_start is None else wait_incrementing_start
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self._wait_incrementing_increment = 100 if wait_incrementing_increment is None else wait_incrementing_increment
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self._wait_exponential_multiplier = 1 if wait_exponential_multiplier is None else wait_exponential_multiplier
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self._wait_exponential_max = MAX_WAIT if wait_exponential_max is None else wait_exponential_max
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self._wait_jitter_max = 0 if wait_jitter_max is None else wait_jitter_max
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# TODO add chaining of stop behaviors
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# stop behavior
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stop_funcs = []
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if stop_max_attempt_number is not None:
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stop_funcs.append(self.stop_after_attempt)
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if stop_max_delay is not None:
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stop_funcs.append(self.stop_after_delay)
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if stop_func is not None:
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self.stop = stop_func
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elif stop is None:
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self.stop = lambda attempts, delay: any(f(attempts, delay) for f in stop_funcs)
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else:
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self.stop = getattr(self, stop)
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# TODO add chaining of wait behaviors
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# wait behavior
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wait_funcs = [lambda *args, **kwargs: 0]
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if wait_fixed is not None:
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wait_funcs.append(self.fixed_sleep)
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if wait_random_min is not None or wait_random_max is not None:
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wait_funcs.append(self.random_sleep)
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if wait_incrementing_start is not None or wait_incrementing_increment is not None:
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wait_funcs.append(self.incrementing_sleep)
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if wait_exponential_multiplier is not None or wait_exponential_max is not None:
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wait_funcs.append(self.exponential_sleep)
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if wait_func is not None:
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self.wait = wait_func
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elif wait is None:
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self.wait = lambda attempts, delay: max(f(attempts, delay) for f in wait_funcs)
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else:
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self.wait = getattr(self, wait)
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# retry on exception filter
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if retry_on_exception is None:
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self._retry_on_exception = self.always_reject
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else:
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self._retry_on_exception = retry_on_exception
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# TODO simplify retrying by Exception types
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# retry on result filter
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if retry_on_result is None:
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self._retry_on_result = self.never_reject
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else:
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self._retry_on_result = retry_on_result
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self._wrap_exception = wrap_exception
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def stop_after_attempt(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""Stop after the previous attempt >= stop_max_attempt_number."""
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return previous_attempt_number >= self._stop_max_attempt_number
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def stop_after_delay(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""Stop after the time from the first attempt >= stop_max_delay."""
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return delay_since_first_attempt_ms >= self._stop_max_delay
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def no_sleep(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""Don't sleep at all before retrying."""
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return 0
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def fixed_sleep(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""Sleep a fixed amount of time between each retry."""
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return self._wait_fixed
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def random_sleep(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""Sleep a random amount of time between wait_random_min and wait_random_max"""
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return random.randint(self._wait_random_min, self._wait_random_max)
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def incrementing_sleep(self, previous_attempt_number, delay_since_first_attempt_ms):
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"""
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Sleep an incremental amount of time after each attempt, starting at
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wait_incrementing_start and incrementing by wait_incrementing_increment
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"""
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result = self._wait_incrementing_start + (self._wait_incrementing_increment * (previous_attempt_number - 1))
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if result < 0:
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result = 0
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return result
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def exponential_sleep(self, previous_attempt_number, delay_since_first_attempt_ms):
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exp = 2 ** previous_attempt_number
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result = self._wait_exponential_multiplier * exp
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if result > self._wait_exponential_max:
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result = self._wait_exponential_max
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if result < 0:
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result = 0
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return result
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def never_reject(self, result):
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return False
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def always_reject(self, result):
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return True
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def should_reject(self, attempt):
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reject = False
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if attempt.has_exception:
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reject |= self._retry_on_exception(attempt.value[1])
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else:
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reject |= self._retry_on_result(attempt.value)
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return reject
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def call(self, fn, *args, **kwargs):
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start_time = int(round(time.time() * 1000))
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attempt_number = 1
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while True:
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try:
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attempt = Attempt(fn(*args, **kwargs), attempt_number, False)
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except:
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tb = sys.exc_info()
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attempt = Attempt(tb, attempt_number, True)
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if not self.should_reject(attempt):
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return attempt.get(self._wrap_exception)
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delay_since_first_attempt_ms = int(round(time.time() * 1000)) - start_time
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if self.stop(attempt_number, delay_since_first_attempt_ms):
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if not self._wrap_exception and attempt.has_exception:
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# get() on an attempt with an exception should cause it to be raised, but raise just in case
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raise attempt.get()
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else:
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raise RetryError(attempt)
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else:
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sleep = self.wait(attempt_number, delay_since_first_attempt_ms)
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if self._wait_jitter_max:
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jitter = random.random() * self._wait_jitter_max
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sleep = sleep + max(0, jitter)
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time.sleep(sleep / 1000.0)
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attempt_number += 1
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class Attempt(object):
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"""
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An Attempt encapsulates a call to a target function that may end as a
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normal return value from the function or an Exception depending on what
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occurred during the execution.
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"""
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def __init__(self, value, attempt_number, has_exception):
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self.value = value
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self.attempt_number = attempt_number
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self.has_exception = has_exception
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def get(self, wrap_exception=False):
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"""
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Return the return value of this Attempt instance or raise an Exception.
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If wrap_exception is true, this Attempt is wrapped inside of a
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RetryError before being raised.
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"""
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if self.has_exception:
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if wrap_exception:
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raise RetryError(self)
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else:
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six.reraise(self.value[0], self.value[1], self.value[2])
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else:
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return self.value
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def __repr__(self):
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if self.has_exception:
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return "Attempts: {0}, Error:\n{1}".format(self.attempt_number, "".join(traceback.format_tb(self.value[2])))
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else:
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return "Attempts: {0}, Value: {1}".format(self.attempt_number, self.value)
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class RetryError(Exception):
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"""
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A RetryError encapsulates the last Attempt instance right before giving up.
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"""
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def __init__(self, last_attempt):
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self.last_attempt = last_attempt
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def __str__(self):
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return "RetryError[{0}]".format(self.last_attempt)
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