Reloadable

Reruns a function upon failure

Reloadable

The function my_func will run indefinitely until it stops raising exceptions, which will never happen in this case.

from reloadable import reloadable

@reloadable()
def my_func():
    raise Exception('Oops')

This module is useful when we want to run something forever, like a code that connects to a queue en fetches messages. Eventually it may disconnect and raise an error trying to fetch a message, so reloadable can retry connecting.

@reloadable()
def get_message():
    conn = Queue(host='...', password='...')

    while True:
        message = conn.fetch_message()
        # probably process message afterwards...

You can config a callback function that receives an exception, which will be called if it occurs.

def shit_happens(exception):
    logger.exception(exception)

@reloadable(exception_callback=shit_happens)
def dont_stop():
    raise Exception('Deal with it')

You can also wait some time before the next respawn

@reloadable(sleep_time=7)  # wait 7 seconds before running `get_message` after a failure
def get_message():
    # some code...

You can always stop reloadable with a KeyboardInterrupt exception (usually triggered by ^C, but not necessarily).

Another option is to configure the stop condition exception.

@reloadable(stop_condition_exception=ValueError)
def i_will_stop():
    raise ValueError('something went wrong')

Or you can define it globally, which will be used if local stop condition wasn’t defined

from reloadable import reloadable, configure

configure(stop_condition_exception=KeyError)

@reloadable()
def i_will_stop():
    raise KeyError('...')

You may also want to limit the number of times that the decorator should try rerun the function. If the function is called max_reloads times without a success, it raises the last error.

from reloadable import reloadable

@reloadable(max_reloads=2)
def a_func():
    raise KeyError('...')

Alternatively you can disable the reloadable decorator via configuration, which is useful during unittests.

from reloadable import configure, reloadable

configure(enabled=False)

@reloadable()  # When disabled, it does nothing
def i_am_free():
    return '\o/'

Retry on Error

The @retry_on_error decorator is useful when you want to retry something on error, but return the result once the decorated function finishes it’s execution with success.

import requests
from reloadable.decorators import retry_on_error


@retry_on_error(max_reloads=3)
def my_request():
    response = requests.get("https://www.sieve.com.br")

    # raises an error for 4xx and 5xx status codes
    response.raise_for_status()

    return response.content