# Copyright (c) 2021 Ansible Project
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# This code is part of Ansible, but is an independent component.
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# to the complete work.
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# are permitted provided that the following conditions are met:
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from __future__ import (absolute_import, division, print_function)
__metaclass__ = type
import time
import functools
import random
import ansible.module_utils.common.warnings as ansible_warnings
class BackoffIterator:
"""iterate sleep value based on the exponential or jitter back-off algorithm.
Args:
delay (int or float): initial delay.
backoff (int or float): backoff multiplier e.g. value of 2 will double the delay each retry.
max_delay (int or None): maximum amount of time to wait between retries.
jitter (bool): if set to true, add jitter to the generate value.
"""
def __init__(self, delay, backoff, max_delay=None, jitter=False):
self.delay = delay
self.backoff = backoff
self.max_delay = max_delay
self.jitter = jitter
def __iter__(self):
self.current_delay = self.delay
return self
def __next__(self):
return_value = self.current_delay if self.max_delay is None else min(self.current_delay, self.max_delay)
if self.jitter:
return_value = random.uniform(0.0, return_value)
self.current_delay *= self.backoff
return return_value
def _retry_func(func, sleep_time_generator, retries, catch_extra_error_codes, found_f, status_code_from_except_f, base_class):
counter = 0
for sleep_time in sleep_time_generator:
try:
return func()
except Exception as exc: # pylint: disable=broad-except
counter += 1
if counter == retries:
raise
if base_class and not isinstance(exc, base_class):
raise
status_code = status_code_from_except_f(exc)
if found_f(status_code, catch_extra_error_codes):
time.sleep(sleep_time)
else:
raise
class CloudRetry:
"""
The base class to be used by other cloud providers to provide a backoff/retry decorator based on status codes.
"""
base_class = type(None)
@staticmethod
def status_code_from_exception(error):
"""
Returns the Error 'code' from an exception.
Args:
error: The Exception from which the error code is to be extracted.
error will be an instance of class.base_class.
"""
raise NotImplementedError()
@staticmethod
def found(response_code, catch_extra_error_codes=None):
def _is_iterable():
try:
iter(catch_extra_error_codes)
except TypeError:
# not iterable
return False
else:
# iterable
return True
return _is_iterable() and response_code in catch_extra_error_codes
@classmethod
def base_decorator(cls, retries, found, status_code_from_exception, catch_extra_error_codes, sleep_time_generator):
def retry_decorator(func):
@functools.wraps(func)
def _retry_wrapper(*args, **kwargs):
partial_func = functools.partial(func, *args, **kwargs)
return _retry_func(
func=partial_func,
sleep_time_generator=sleep_time_generator,
retries=retries,
catch_extra_error_codes=catch_extra_error_codes,
found_f=found,
status_code_from_except_f=status_code_from_exception,
base_class=cls.base_class,
)
return _retry_wrapper
return retry_decorator
@classmethod
def exponential_backoff(cls, retries=10, delay=3, backoff=2, max_delay=60, catch_extra_error_codes=None):
"""Wrap a callable with retry behavior.
Args:
retries (int): Number of times to retry a failed request before giving up
default=10
delay (int or float): Initial delay between retries in seconds
default=3
backoff (int or float): backoff multiplier e.g. value of 2 will double the delay each retry
default=2
max_delay (int or None): maximum amount of time to wait between retries.
default=60
catch_extra_error_codes: Additional error messages to catch, in addition to those which may be defined by a subclass of CloudRetry
default=None
Returns:
Callable: A generator that calls the decorated function using an exponential backoff.
"""
sleep_time_generator = BackoffIterator(delay=delay, backoff=backoff, max_delay=max_delay)
return cls.base_decorator(
retries=retries,
found=cls.found,
status_code_from_exception=cls.status_code_from_exception,
catch_extra_error_codes=catch_extra_error_codes,
sleep_time_generator=sleep_time_generator,
)
@classmethod
def jittered_backoff(cls, retries=10, delay=3, backoff=2.0, max_delay=60, catch_extra_error_codes=None):
"""Wrap a callable with retry behavior.
Args:
retries (int): Number of times to retry a failed request before giving up
default=10
delay (int or float): Initial delay between retries in seconds
default=3
backoff (int or float): backoff multiplier e.g. value of 2 will double the delay each retry
default=2.0
max_delay (int or None): maximum amount of time to wait between retries.
default=60
catch_extra_error_codes: Additional error messages to catch, in addition to those which may be defined by a subclass of CloudRetry
default=None
Returns:
Callable: A generator that calls the decorated function using using a jittered backoff strategy.
"""
sleep_time_generator = BackoffIterator(delay=delay, backoff=backoff, max_delay=max_delay, jitter=True)
return cls.base_decorator(
retries=retries,
found=cls.found,
status_code_from_exception=cls.status_code_from_exception,
catch_extra_error_codes=catch_extra_error_codes,
sleep_time_generator=sleep_time_generator,
)
@classmethod
def backoff(cls, tries=10, delay=3, backoff=1.1, catch_extra_error_codes=None):
"""
Wrap a callable with retry behavior.
Developers should use CloudRetry.exponential_backoff instead.
This method has been deprecated and will be removed in release 6.0.0, consider using exponential_backoff method instead.
Args:
retries (int): Number of times to retry a failed request before giving up
default=10
delay (int or float): Initial delay between retries in seconds
default=3
backoff (int or float): backoff multiplier e.g. value of 2 will double the delay each retry
default=1.1
catch_extra_error_codes: Additional error messages to catch, in addition to those which may be defined by a subclass of CloudRetry
default=None
Returns:
Callable: A generator that calls the decorated function using an exponential backoff.
"""
# This won't emit a warning (we don't have the context available to us), but will trigger
# sanity failures as we prepare for 6.0.0
ansible_warnings.deprecate(
'CloudRetry.backoff has been deprecated, please use CloudRetry.exponential_backoff instead',
version='6.0.0', collection_name='amazon.aws')
return cls.exponential_backoff(
retries=tries,
delay=delay,
backoff=backoff,
max_delay=None,
catch_extra_error_codes=catch_extra_error_codes,
)