tractor/tests/test_cancellation.py

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"""
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
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@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.
"""
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args, errtype = args_err
async def main():
async with tractor.open_nursery() as nursery:
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portal = await nursery.run_in_actor('errorer', assert_err, **args)
# get result(s) from main task
try:
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await portal.result()
except tractor.RemoteActorError as err:
assert err.type == errtype
print("Look Maa that actor failed hard, hehh")
raise
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else:
assert 0, "Remote error was not raised?"
with pytest.raises(tractor.RemoteActorError):
# also raises
tractor.run(main, arbiter_addr=arb_addr)
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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):
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"""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()
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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
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@pytest.mark.parametrize(
'num_actors_and_errs',
[
(1, tractor.RemoteActorError, AssertionError),
(2, tractor.MultiError, AssertionError)
],
ids=['one_actor', 'two_actors'],
)
@tractor_test
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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.
"""
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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__],
))
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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`
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except first_err as err:
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if isinstance(err, tractor.MultiError):
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assert len(err.exceptions) == num
for exc in err.exceptions:
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if isinstance(exc, tractor.RemoteActorError):
assert exc.type == err_type
else:
assert isinstance(exc, trio.Cancelled)
elif isinstance(err, tractor.RemoteActorError):
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assert err.type == err_type
assert n.cancelled is True
assert not n._children
else:
pytest.fail("Should have gotten a remote assertion error?")