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tractor/tests/test_cancellation.py

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Python

"""
Cancellation and error propagation
"""
from itertools import repeat
import pytest
import trio
import tractor
from conftest import tractor_test
async def assert_err():
assert 0
@pytest.mark.parametrize(
'args_err',
[
# expected to be thrown in assert_err
({}, AssertionError),
# argument mismatch raised in _invoke()
({'unexpected': 10}, TypeError)
],
ids=['no_args', 'unexpected_args'],
)
def test_remote_error(arb_addr, args_err):
"""Verify an error raised in a subactor that is propagated
to the parent nursery, contains underlying builtin erorr type
infot and causes cancellation and reraising.
"""
args, errtype = args_err
async def main():
async with tractor.open_nursery() as nursery:
portal = await nursery.run_in_actor('errorer', assert_err, **args)
# get result(s) from main task
try:
await portal.result()
except tractor.RemoteActorError as err:
assert err.type == errtype
print("Look Maa that actor failed hard, hehh")
raise
else:
assert 0, "Remote error was not raised?"
with pytest.raises(tractor.RemoteActorError):
# also raises
tractor.run(main, arbiter_addr=arb_addr)
def test_multierror(arb_addr):
"""Verify we raise a ``trio.MultiError`` out of a nursery where
more then one actor errors.
"""
async def main():
async with tractor.open_nursery() as nursery:
await nursery.run_in_actor('errorer1', assert_err)
portal2 = await nursery.run_in_actor('errorer2', assert_err)
# get result(s) from main task
try:
await portal2.result()
except tractor.RemoteActorError as err:
assert err.type == AssertionError
print("Look Maa that first actor failed hard, hehh")
raise
# here we should get a `trio.MultiError` containing exceptions
# from both subactors
with pytest.raises(trio.MultiError):
tractor.run(main, arbiter_addr=arb_addr)
def do_nothing():
pass
def test_cancel_single_subactor(arb_addr):
"""Ensure a ``ActorNursery.start_actor()`` spawned subactor
cancels when the nursery is cancelled.
"""
async def spawn_actor():
"""Spawn an actor that blocks indefinitely.
"""
async with tractor.open_nursery() as nursery:
portal = await nursery.start_actor(
'nothin', rpc_module_paths=[__name__],
)
assert (await portal.run(__name__, 'do_nothing')) is None
# would hang otherwise
await nursery.cancel()
tractor.run(spawn_actor, arbiter_addr=arb_addr)
async def stream_forever():
for i in repeat("I can see these little future bubble things"):
# each yielded value is sent over the ``Channel`` to the
# parent actor
yield i
await trio.sleep(0.01)
@tractor_test
async def test_cancel_infinite_streamer():
# stream for at most 1 seconds
with trio.move_on_after(1) as cancel_scope:
async with tractor.open_nursery() as n:
portal = await n.start_actor(
f'donny',
rpc_module_paths=[__name__],
)
# this async for loop streams values from the above
# async generator running in a separate process
async for letter in await portal.run(__name__, 'stream_forever'):
print(letter)
# we support trio's cancellation system
assert cancel_scope.cancelled_caught
assert n.cancelled
@pytest.mark.parametrize(
'num_actors_and_errs',
[
(1, tractor.RemoteActorError, AssertionError),
(2, tractor.MultiError, AssertionError)
],
ids=['one_actor', 'two_actors'],
)
@tractor_test
async def test_some_cancels_all(num_actors_and_errs):
"""Verify one failed actor causes all others in the nursery
to be cancelled just like in trio.
This is the first and only supervisory strategy at the moment.
"""
num, first_err, err_type = num_actors_and_errs
try:
async with tractor.open_nursery() as n:
real_actors = []
for i in range(3):
real_actors.append(await n.start_actor(
f'actor_{i}',
rpc_module_paths=[__name__],
))
for i in range(num):
# start one actor that will fail immediately
await n.run_in_actor(f'extra_{i}', assert_err)
# should error here with a ``RemoteActorError`` or
# ``MultiError`` containing an ``AssertionError`
except first_err as err:
if isinstance(err, tractor.MultiError):
assert len(err.exceptions) == num
for exc in err.exceptions:
if isinstance(exc, tractor.RemoteActorError):
assert exc.type == err_type
else:
assert isinstance(exc, trio.Cancelled)
elif isinstance(err, tractor.RemoteActorError):
assert err.type == err_type
assert n.cancelled is True
assert not n._children
else:
pytest.fail("Should have gotten a remote assertion error?")