Retry calling the decorated function using an exponential backoff.

    http://www.saltycrane.com/blog/2009/11/trying-out-retry-decorator-python/
    original from: http://wiki.python.org/moin/PythonDecoratorLibrary#Retry

    :param target_exception: the exception to check. may be a tuple of
        exceptions to check
    :type target_exception: Exception or tuple
    :param tries: number of times to try (not retry) before giving up
    :type tries: int
    :param delay_s: initial delay between retries in seconds
    :type delay_s: int
    :param backoff: backoff multiplier e.g. value of 2 will double the delay
        each retry
    :type backoff: int

def retry(target_exception, tries=4, delay_s=1, backoff=2):
    """Retry calling the decorated function using an exponential backoff.

    http://www.saltycrane.com/blog/2009/11/trying-out-retry-decorator-python/
    original from: http://wiki.python.org/moin/PythonDecoratorLibrary#Retry

    :param target_exception: the exception to check. may be a tuple of
        exceptions to check
    :type target_exception: Exception or tuple
    :param tries: number of times to try (not retry) before giving up
    :type tries: int
    :param delay_s: initial delay between retries in seconds
    :type delay_s: int
    :param backoff: backoff multiplier e.g. value of 2 will double the delay
        each retry
    :type backoff: int
    """
    import time
    from functools import wraps

    def decorated_retry(f):
        @wraps(f)
        def f_retry(*args, **kwargs):
            mtries, mdelay = tries, delay_s
            while mtries > 1:
                try:
                    return f(*args, **kwargs)
                except target_exception as e:
                    logging.warning("Exception: %s, Retrying in %d seconds...", str(e), mdelay)
                    time.sleep(mdelay)
                    mtries -= 1
                    mdelay *= backoff
            return f(*args, **kwargs)

        return f_retry  # true decorator

    return decorated_retry