ahmedalanim / retry

easy to use retry decorator in python

retry

Easy to use retry decorator.

Features

• No external dependency (stdlib only).
• (Optionally) Preserve function signatures (pip install decorator).
• Original traceback, easy to debug.

Installation

$ pip install retry

API

retry decorator

def retry(exceptions=Exception, tries=-1, delay=0, max_delay=None, backoff=1, jitter=0, logger=logging_logger, error_code=[]):
    """Return a retry decorator.

    :param exceptions: an exception or a tuple of exceptions to catch. default: Exception.
    :param tries: the maximum number of attempts. default: -1 (infinite).
    :param delay: initial delay between attempts. default: 0.
    :param max_delay: the maximum value of delay. default: None (no limit).
    :param backoff: multiplier applied to delay between attempts. default: 1 (no backoff).
    :param jitter: extra seconds added to delay between attempts. default: 0.
                   fixed if a number, random if a range tuple (min, max)
    :param logger: logger.warning(fmt, error, delay) will be called on failed attempts.
                   default: retry.logging_logger. if None, logging is disabled.
    :param error_code: A list of Botocore Exception Error Code. For failed attempts, if a list of error code provided,
                  exception will be raised immediately if the error does not match

    """

Various retrying logic can be achieved by combination of arguments.

Examples

from retry import retry

@retry()
def make_trouble():
    '''Retry until succeed'''

@retry(ZeroDivisionError, tries=3, delay=2)
def make_trouble():
    '''Retry on ZeroDivisionError, raise error after 3 attempts, sleep 2 seconds between attempts.'''

@retry((ValueError, TypeError), delay=1, backoff=2)
def make_trouble():
    '''Retry on ValueError or TypeError, sleep 1, 2, 4, 8, ... seconds between attempts.'''

@retry((ValueError, TypeError), delay=1, backoff=2, max_delay=4)
def make_trouble():
    '''Retry on ValueError or TypeError, sleep 1, 2, 4, 4, ... seconds between attempts.'''

@retry(ValueError, delay=1, jitter=1)
def make_trouble():
    '''Retry on ValueError, sleep 1, 2, 3, 4, ... seconds between attempts.'''

@retry(botocore.exceptions.ClientError, delay=1, jitter=1, error_code=["InternalFailure"])
def make_trouble():
    '''Retry on ClientError as long as Error Code InternalFailure, sleep 1, 2, 3, 4, ... seconds between attempts.

       Raises exception immediately if error code is anything but InternalFailure.
    '''

# If you enable logging, you can get warnings like 'ValueError, retrying in
# 1 seconds'
if __name__ == '__main__':
    import logging
    logging.basicConfig()
    make_trouble()

retry_call

def retry_call(f, fargs=None, fkwargs=None, exceptions=Exception, tries=-1, delay=0, max_delay=None, backoff=1,
               jitter=0,
               logger=logging_logger):
    """
    Calls a function and re-executes it if it failed.

    :param f: the function to execute.
    :param fargs: the positional arguments of the function to execute.
    :param fkwargs: the named arguments of the function to execute.
    :param exceptions: an exception or a tuple of exceptions to catch. default: Exception.
    :param tries: the maximum number of attempts. default: -1 (infinite).
    :param delay: initial delay between attempts. default: 0.
    :param max_delay: the maximum value of delay. default: None (no limit).
    :param backoff: multiplier applied to delay between attempts. default: 1 (no backoff).
    :param jitter: extra seconds added to delay between attempts. default: 0.
                   fixed if a number, random if a range tuple (min, max)
    :param logger: logger.warning(fmt, error, delay) will be called on failed attempts.
                   default: retry.logging_logger. if None, logging is disabled.
    :param error_code: A list of Botocore Exception Error Code. For failed attempts, if a list of error code provided,
                  exception will be raised immediately if the error does not matc
    :returns: the result of the f function.
    """

This is very similar to the decorator, except that it takes a function and its arguments as parameters. The use case behind it is to be able to dynamically adjust the retry arguments.

import requests

from retry.api import retry_call


def make_trouble(service, info=None):
    if not info:
        info = ''
    r = requests.get(service + info)
    return r.text


def what_is_my_ip(approach=None):
    if approach == "optimistic":
        tries = 1
    elif approach == "conservative":
        tries = 3
    else:
        # skeptical
        tries = -1
    result = retry_call(make_trouble, fargs=["http://ipinfo.io/"], fkwargs={"info": "ip"}, tries=tries)
    print(result)

what_is_my_ip("conservative")