python retrying重试模块 功能类似retry模块

安装

pip?install?retrying

官方网址：

https://github.com/rholder/retrying

API 介绍

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
	?)

stop_max_attempt_number：用来设定最大的尝试次数，超过该次数就停止重试

stop_max_delay：比如设置成10000，那么从被装饰的函数开始执行的时间点开始，到函数成功运行结束或者失败报错中止的时间点，只要这段时间超过10秒，函数就不会再执行了

wait_fixed：设置在两次retrying之间的停留时间

wait_random_min和wait_random_max：用随机的方式产生两次retrying之间的停留时间

wait_exponential_multiplier和wait_exponential_max：以指数的形式产生两次retrying之间的停留时间，产生的值为2^previous_attempt_number * wait_exponential_multiplier，previous_attempt_number是前面已经retry的次数，如果产生的这个值超过了wait_exponential_max的大小，那么之后两个retrying之间的停留值都为wait_exponential_max

我们可以指定要在出现哪些异常的时候再去retry，这个要用retry_on_exception传入一个函数对象

列子

1.??@retry装饰器，如出现异常会一直重试

@retry
def?never_give_up_never_surrender():
????print?"Retry?forever?ignoring?Exceptions,?don't?wait?between?retries"

2.??stop_max_attempt_number 设置最大重试次数

@retry(stop_max_attempt_number=7)
def?stop_after_7_attempts():
????print?"Stopping?after?7?attempts"
????raise

3.?stop_max_delay 设置失败重试的最大时间,单位毫秒，超出时间，则停止重试

@retry(stop_max_delay=10000)
def?stop_after_10_s():
????print?"Stopping?after?10?seconds"
????raise

4.?wait_fixed 设置失败重试的间隔时间

@retry(wait_fixed=2000,?stop_max_delay=10000)
def?wait_2_s():
????print?"Wait?2?second?between?retries"
????raise

5.?wait_random_min,wait_random_max 设置失败重试随机性间隔时间

@retry(wait_random_min=1000,?wait_random_max=5000,?stop_max_delay=10000)
def?wait_random_1_to_5_s():
????print?"Randomly?wait?1?to?5?seconds?between?retries"
????raise

6.?wait_exponential_multiplier-间隔时间倍数增加，wait_exponential_max-最大间隔时间

import?time

@retry(wait_exponential_multiplier=1000,?wait_exponential_max=10000)
def?wait_exponential_1000():
????print?"Wait?2^x?*?1000?milliseconds?between?each?retry,?up?to?10?seconds,?then?10?seconds?afterwards"
????print?int(time.time())
????raise

输出：
Wait?2^x?*?1000?milliseconds?between?each?retry,?then?10?seconds?afterwards
1504110314
Wait?2^x?*?1000?milliseconds?between?each?retry,?then?10?seconds?afterwards
1504110316
Wait?2^x?*?1000?milliseconds?between?each?retry,?then?10?seconds?afterwards
1504110320
Wait?2^x?*?1000?milliseconds?between?each?retry,?then?10?seconds?afterwards
1504110328
Wait?2^x?*?1000?milliseconds?between?each?retry,?then?10?seconds?afterwards
1504110338
Wait?2^x?*?1000?milliseconds?between?each?retry,?then?10?seconds?afterwards
1504110348

7.?retry_on_exception指定异常类型，指定的异常类型会重试，不指定的类型，会直接异常退出，wrap_exception参数设置为True，则其他类型异常，或包裹在RetryError中，会看到RetryError和程序抛的Exception error

def?retry_if_io_error(exception):
????"""Return?True?if?we?should?retry?(in?this?case?when?it's?an?IOError),?False?otherwise"""
????return?isinstance(exception,?IOError)

@retry(retry_on_exception=retry_if_io_error)
def?might_io_error():
????print?"Retry?forever?with?no?wait?if?an?IOError?occurs,?raise?any?other?errors"
????raise?Exception('a')


@retry(retry_on_exception=retry_if_io_error,?wrap_exception=True)
def?only_raise_retry_error_when_not_io_error():
????print?"Retry?forever?with?no?wait?if?an?IOError?occurs,?raise?any?other?errors?wrapped?in?RetryError"
????raise?Exception('a')

8.?retry_on_result,指定要在得到哪些结果的时候去retry，retry_on_result传入一个函数对象,在执行get_result成功后，会将函数的返回值通过形参result的形式传入retry_if_result_none函数中，如果返回值是None那么就进行retry，否则就结束并返回函数值

def?retry_if_result_none(result):
????return?result?is?None

@retry(retry_on_result=retry_if_result_none)
def?get_result():
????print?'Retry?forever?ignoring?Exceptions?with?no?wait?if?return?value?is?None'
????return?None

原文：https://segmentfault.com/a/1190000004085023

（编辑：李大同）

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