retrying.py - third_party/github.com/jd/tenacity - Git at Google

 ## 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
 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)
	## 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
	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)