simple_retry.py

import os
import sys
from functools import wraps

import gevent
import six

sys.stderr = open(os.devnull, 'w')


class DoRetry(object):

    def __init__(self, times=2, interval=5, exponential_interval=True, inject_attempts=True):
        if not (interval > 0 and isinstance(times, int) and times > 0):
            raise AttributeError('interval and times must be a positive')
        self.times = times
        self.interval = interval
        self.is_exponential = exponential_interval
        self.inject_attempts = inject_attempts

    def __call__(self, func, *args, **kwargs):
        @wraps(func)
        def wrap(*args, **kwargs):
            try_after = 0
            elapsed = 0
            while True:
                elapsed += 1
                gevent.sleep(try_after)
                try:
                    if self.inject_attempts:
                        kwargs.update({'attempts': elapsed})
                    retval = func(*args, **kwargs)
                    break
                except Exception as e:
                    if self.times > elapsed:
                        if self.is_exponential:
                            try_after = self.interval ** elapsed
                        else:
                            try_after = self.interval
                    else:
                        ret = 'failed after %s %s' % (elapsed, 'try' if elapsed <= 1 else 'tries')
                        ex = RuntimeError(ret)
                        six.raise_from(e, ex)
            return retval
        return wrap


@DoRetry(3, 3, inject_attempts=False)
def function_fails_forever(**kwargs):
    func_name = 'function_fails_forever'
    counter = kwargs.get('attempts', 0)
    print('attempting %s' % func_name)
    if counter < 3:
        raise Exception("counter has not met particaular criteria")
    return "%s ~ retries successful after %s times" % (func_name, counter)


@DoRetry(3, 3)
def function_succeeds_after_retries(**kwargs):
    func_name = 'function_succeeds_after_retries'
    counter = kwargs.get('attempts', 0)
    print ('%s ~ attempt %s' % (func_name, counter))
    if counter < 3:
        raise Exception("counter has not met particaular criteria")
    return "%s ~ retries successful after %s times" % (func_name, counter)


if __name__ == '__main__':
    g1 = gevent.spawn(function_fails_forever)
    g2 = gevent.spawn(function_succeeds_after_retries)
    threads = [g1, g2]
    gevent.joinall(threads)
    print('function_fails_forever returned :: %s' % (g1.value))
    print('function_succeeds_after_retries returned :: %s' % (g2.value))