trythatagain

This provides decorators for super simple function/method call retries when an exception is raised.

Installation

pip install trythatagain

Examples

Here's a simple use case: querying the AWS API, knowing you might hit API limits.

from trythatagain import retry

@retry
def find_ebs_volumes(unattached=True, no_snapshots=True):
    ...

try:
    find_ebs_volumes()
except CaughtException as e:
    print('Failed to list EBS volumes')
    print(e.caught_exception)

This will retry calling func three times. If was not successful in calling the function without an exception, it will re-raise the exception as CaughtException, with the original exception available at the attribute caught_exception.

Retry as many times as times as necessary:

from trythatagain import retry

@retry(retries=5)
def try_five_times():
    raise Exception('This always fails')

@retry(retries=0)
def retry_forever():
    raise Exception('Terrible waste of CPU cycles')

Raise immediately on specific exceptions:

@retry(raise_for=ValueError)
def update_cache():
    ...

Suppress re-raising exceptions:

@retry(reraise=False)
def reload_user_data():
    ...

There's also exponential and linear backoff retries things like cooling down after hitting API limits. In fact, AWS recommends exponential backoff to deal with API limits.

# waits 1 second, then 4, then 9, etc.
@retry_exp_backoff(unit=MILLISECONDS)
def update_instance_tags():
    ...

@retry_linear_backoff(unit=SECONDS)
def scrape_url():
    ...

Custom wait functions are also possible:

def fixed(i, unit):
    time.sleep(5 * unit)

@retry(wait_func=fixed, unit=MILLISECONDS)
def func():
    ...