Support retry on failed tasks

[imranariffin]

Retry failed task if specified in task definition or in task call

import asyncio

from aiotaskq.task import task


class SomeException(Exception):
    pass


class SomeOtherException(Exception):
    pass


@task(retry=(3, SomeException))
def some_task_1():
    raise SomeException


@task()
def some_task_2():
    raise SomeException


async def apply_tasks():
    # Will be retried 3 times, as specified in task definition
    try:
        await some_task_1.apply_async()
    except SomeException as e:
        assert e.aiotaskq.retries == 3

    # Will be retried 2 times, as specified in task call (retry configuration from task
    # definition has been overridden)
    try:
        await some_task_1.retry((1, SomeException)).apply_async()
    except SomeException as e:
        assert e.aiotaskq.retries == 2

    # Will NOT be retried (retry configuration from task definition is overridden)
    try:
        await some_task_1.retry((1, SomeOtherException)).apply_async()
    except SomeException as e:
        assert e.aiotaskq.retries == 0
    except SomeOtherException as e:
        assert False, "Should not reach here"

    # Will be retried 1 time, as specified in task call
    try:
        await some_task_2.retry((1, SomeException)).apply_async()
    except SomeException as e:
        assert e.aiotaskq.retries == 1


if __name__ == "__main__":
    asyncio.run(apply_tasks())