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Fix `asyncio`-task-sync and error propagation 

This fixes an previously undetected bug where if an
`.open_channel_from()` spawned task errored the error would not be
propagated to the `trio` side and instead would fail silently with
a console log error. What was most odd is that it only seems easy to
trigger when you put a slight task sleep before the error is raised
(:eyeroll:). This patch adds a few things to address this and just in
general improve iter-task lifetime syncing:

- add `LinkedTaskChannel._trio_exited: bool` a flag set from the `trio`
  side when the channel block exits.
- add a `wait_on_aio_task: bool` flag to `translate_aio_errors` which
  toggles whether to wait the `asyncio` task termination event on exit.
- cancel the `asyncio` task if the trio side has ended, when
  `._trio_exited == True`.
- always close the `trio` mem channel when the task exits such that
  the `asyncio` side can error on any next `.send()` call.
aio_error_propagation^2
Tyler Goodlet 2022-07-14 16:35:41 -04:00
parent 98de2fab31
commit 38d03858d7
2 changed files with 54 additions and 13 deletions
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2
tests/test_infected_asyncio.py
View File

@ -185,7 +185,7 @@ async def trio_ctx(
tractor.to_asyncio.run_task,
sleep_forever,
)
# await trio.sleep_forever()
await trio.sleep_forever()
@pytest.mark.parametrize(

65
tractor/to_asyncio.py
View File

@ -63,6 +63,7 @@ class LinkedTaskChannel(trio.abc.Channel):
_trio_cs: trio.CancelScope
_aio_task_complete: trio.Event
_trio_exited: bool = False
# set after ``asyncio.create_task()``
_aio_task: Optional[asyncio.Task] = None
@ -73,7 +74,13 @@ class LinkedTaskChannel(trio.abc.Channel):
await self._from_aio.aclose()
async def receive(self) -> Any:
async with translate_aio_errors(self):
async with translate_aio_errors(
self,
# XXX: obviously this will deadlock if an on-going stream is
# being procesed.
# wait_on_aio_task=False,
):
# TODO: do we need this to guarantee asyncio code get's
# cancelled in the case where the trio side somehow creates
@ -210,10 +217,8 @@ def _run_asyncio_task(
orig = result = id(coro)
try:
result = await coro
except GeneratorExit:
# no need to relay error
raise
except BaseException as aio_err:
log.exception('asyncio task errored')
chan._aio_err = aio_err
raise
@ -237,6 +242,7 @@ def _run_asyncio_task(
to_trio.close()
aio_task_complete.set()
log.runtime(f'`asyncio` task: {task.get_name()} is complete')
# start the asyncio task we submitted from trio
if not inspect.isawaitable(coro):
@ -296,6 +302,11 @@ def _run_asyncio_task(
f'infected task errorred:\n{msg}'
)
# XXX: alway cancel the scope on error
# in case the trio task is blocking
# on a checkpoint.
cancel_scope.cancel()
# raise any ``asyncio`` side error.
raise aio_err
@ -307,6 +318,7 @@ def _run_asyncio_task(
async def translate_aio_errors(
chan: LinkedTaskChannel,
wait_on_aio_task: bool = False,
) -> AsyncIterator[None]:
'''
@ -318,6 +330,7 @@ async def translate_aio_errors(
aio_err: Optional[BaseException] = None
# TODO: make thisi a channel method?
def maybe_raise_aio_err(
err: Optional[Exception] = None
) -> None:
@ -367,13 +380,30 @@ async def translate_aio_errors(
raise
finally:
# always cancel the ``asyncio`` task if we've made it this far
# and it's not done.
if not task.done() and aio_err:
if (
# NOTE: always cancel the ``asyncio`` task if we've made it
# this far and it's not done.
not task.done() and aio_err
# or the trio side has exited it's surrounding cancel scope
# indicating the lifetime of the ``asyncio``-side task
# should also be terminated.
or chan._trio_exited
):
log.runtime(
f'Cancelling `asyncio`-task: {chan._aio_taskget_name()}'
)
# assert not aio_err, 'WTF how did asyncio do this?!'
task.cancel()
# if any ``asyncio`` error was caught, raise it here inline
# Required to sync with the far end ``asyncio``-task to ensure
# any error is captured (via monkeypatching the
# ``channel._aio_err``) before calling ``maybe_raise_aio_err()``
# below!
if wait_on_aio_task:
await chan._aio_task_complete.wait()
# NOTE: if any ``asyncio`` error was caught, raise it here inline
# here in the ``trio`` task
maybe_raise_aio_err()
@ -398,7 +428,10 @@ async def run_task(
**kwargs,
)
with chan._from_aio:
async with translate_aio_errors(chan):
async with translate_aio_errors(
chan,
wait_on_aio_task=True,
):
# return single value that is the output from the
# ``asyncio`` function-as-task. Expect the mem chan api to
# do the job of handling cross-framework cancellations
@ -426,13 +459,21 @@ async def open_channel_from(
**kwargs,
)
async with chan._from_aio:
async with translate_aio_errors(chan):
async with translate_aio_errors(
chan,
wait_on_aio_task=True,
):
# sync to a "started()"-like first delivered value from the
# ``asyncio`` task.
first = await chan.receive()
# deliver stream handle upward
yield first, chan
try:
with chan._trio_cs:
yield first, chan
finally:
chan._trio_exited = True
chan._to_trio.close()
def run_as_asyncio_guest(
@ -482,7 +523,7 @@ def run_as_asyncio_guest(
main_outcome.unwrap()
else:
trio_done_fut.set_result(main_outcome)
print(f"trio_main finished: {main_outcome!r}")
log.runtime(f"trio_main finished: {main_outcome!r}")
# start the infection: run trio on the asyncio loop in "guest mode"
log.info(f"Infecting asyncio process with {trio_main}")