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asyncio cancel all tasks on first task's exception
import asyncio
import logging
from typing import List
def _ignore_task_exception(task: asyncio.Future, logger: logging.Logger):
# noinspection PyBroadException
try:
task.result()
except BaseException:
# These may be things like boto 404s
pass
# logger.info("Ignoring exception", exc_info=sys.exc_info())
async def _wait_task_cancellations(cancelled_tasks: List[asyncio.Task], logger: logging.Logger, loop: asyncio.BaseEventLoop=None, log_cancellation: bool=False, log_exceptions: bool=True):
if not len(cancelled_tasks):
return
# now wait for cancelled tasks to finish and log exceptions encountered
done_futures, _ = await asyncio.wait(cancelled_tasks, loop=loop)
for fut in done_futures:
try:
fut.result()
except asyncio.CancelledError:
if log_cancellation:
logger.exception('Task was cancelled')
except:
if log_exceptions:
logger.exception("Task raised unexpected exception during cancellation")
async def gather_cancel_on_raise(*tasks: Union[asyncio.Task, Coroutine, asyncio.Future], loop: asyncio.BaseEventLoop=None, logger: logging.Logger):
"""
Similar to asyncio.gather, however if any gathering future raises, will
immediately cancel any unfinished tasks. This method is useful if `return_exceptions` is set to
True (default) with the `asyncio.gather` call.
The default asyncio.gather on first task exception will allow the pending tasks to continue and raise
said exception. This leaves unparented tasks.
:param tasks: tasks to pass to `asyncio.gather`
:param loop: loop to pass to `asyncio.gather`
:param logger: logger to use
:return: result of `asyncio.gather`
"""
loop = loop or asyncio.get_event_loop()
tasks: List[asyncio.Future] = [asyncio.ensure_future(task, loop=loop) for task in tasks]
gfut = asyncio.gather(*tasks, loop=loop)
try:
return await gfut
except BaseException as e:
outer_cancelled = isinstance(e, asyncio.CancelledError)
# first cancel all the unfinished tasks
cancelled_tasks = []
# We're reaching into the internals of gather to avoid having to re-implement gather
# We have a unittest to ensure this works correctly going forward
for task in tasks:
if not task.done():
task.cancel()
cancelled_tasks.append(task)
elif task.cancelled() or task.exception():
_ignore_task_exception(task, logger)
await _wait_task_cancellations(cancelled_tasks, logger, loop, not outer_cancelled)
# re-raise outer exception
raise
@thehesiod
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thehesiod commented Feb 1, 2021

@mvolfik cool thanks for tip, updated above

@guishake
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guishake commented Oct 29, 2021

Thanks for this code ! 👍

@artemonsh
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artemonsh commented May 5, 2022

Thanks a lot! Works as expected.
For others: you may want to add
from typing import List, Union, Coroutine

@thehesiod
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thehesiod commented May 5, 2022

👍

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