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from __future__ import annotations
import sys
import threading
from collections.abc import Awaitable, Callable, Generator
from concurrent.futures import FIRST_COMPLETED, Future, ThreadPoolExecutor, wait
from contextlib import AbstractContextManager, contextmanager
from inspect import isawaitable
from types import TracebackType
from typing import (
Any,
AsyncContextManager,
ContextManager,
Generic,
Iterable,
TypeVar,
cast,
overload,
)
from ._core import _eventloop
from ._core._eventloop import get_async_backend, get_cancelled_exc_class, threadlocals
from ._core._synchronization import Event
from ._core._tasks import CancelScope, create_task_group
from .abc import AsyncBackend
from .abc._tasks import TaskStatus
if sys.version_info >= (3, 11):
from typing import TypeVarTuple, Unpack
else:
from typing_extensions import TypeVarTuple, Unpack
T_Retval = TypeVar("T_Retval")
T_co = TypeVar("T_co", covariant=True)
PosArgsT = TypeVarTuple("PosArgsT")
def run(
func: Callable[[Unpack[PosArgsT]], Awaitable[T_Retval]], *args: Unpack[PosArgsT]
) -> T_Retval:
"""
Call a coroutine function from a worker thread.
:param func: a coroutine function
:param args: positional arguments for the callable
:return: the return value of the coroutine function
"""
try:
async_backend = threadlocals.current_async_backend
token = threadlocals.current_token
except AttributeError:
raise RuntimeError(
"This function can only be run from an AnyIO worker thread"
) from None
return async_backend.run_async_from_thread(func, args, token=token)
def run_sync(
func: Callable[[Unpack[PosArgsT]], T_Retval], *args: Unpack[PosArgsT]
) -> T_Retval:
"""
Call a function in the event loop thread from a worker thread.
:param func: a callable
:param args: positional arguments for the callable
:return: the return value of the callable
"""
try:
async_backend = threadlocals.current_async_backend
token = threadlocals.current_token
except AttributeError:
raise RuntimeError(
"This function can only be run from an AnyIO worker thread"
) from None
return async_backend.run_sync_from_thread(func, args, token=token)
class _BlockingAsyncContextManager(Generic[T_co], AbstractContextManager):
_enter_future: Future[T_co]
_exit_future: Future[bool | None]
_exit_event: Event
_exit_exc_info: tuple[
type[BaseException] | None, BaseException | None, TracebackType | None
] = (None, None, None)
def __init__(self, async_cm: AsyncContextManager[T_co], portal: BlockingPortal):
self._async_cm = async_cm
self._portal = portal
async def run_async_cm(self) -> bool | None:
try:
self._exit_event = Event()
value = await self._async_cm.__aenter__()
except BaseException as exc:
self._enter_future.set_exception(exc)
raise
else:
self._enter_future.set_result(value)
try:
# Wait for the sync context manager to exit.
# This next statement can raise `get_cancelled_exc_class()` if
# something went wrong in a task group in this async context
# manager.
await self._exit_event.wait()
finally:
# In case of cancellation, it could be that we end up here before
# `_BlockingAsyncContextManager.__exit__` is called, and an
# `_exit_exc_info` has been set.
result = await self._async_cm.__aexit__(*self._exit_exc_info)
return result
def __enter__(self) -> T_co:
self._enter_future = Future()
self._exit_future = self._portal.start_task_soon(self.run_async_cm)
return self._enter_future.result()
def __exit__(
self,
__exc_type: type[BaseException] | None,
__exc_value: BaseException | None,
__traceback: TracebackType | None,
) -> bool | None:
self._exit_exc_info = __exc_type, __exc_value, __traceback
self._portal.call(self._exit_event.set)
return self._exit_future.result()
class _BlockingPortalTaskStatus(TaskStatus):
def __init__(self, future: Future):
self._future = future
def started(self, value: object = None) -> None:
self._future.set_result(value)
class BlockingPortal:
"""An object that lets external threads run code in an asynchronous event loop."""
def __new__(cls) -> BlockingPortal:
return get_async_backend().create_blocking_portal()
def __init__(self) -> None:
self._event_loop_thread_id: int | None = threading.get_ident()
self._stop_event = Event()
self._task_group = create_task_group()
self._cancelled_exc_class = get_cancelled_exc_class()
async def __aenter__(self) -> BlockingPortal:
await self._task_group.__aenter__()
return self
async def __aexit__(
self,
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
) -> bool | None:
await self.stop()
return await self._task_group.__aexit__(exc_type, exc_val, exc_tb)
def _check_running(self) -> None:
if self._event_loop_thread_id is None:
raise RuntimeError("This portal is not running")
if self._event_loop_thread_id == threading.get_ident():
raise RuntimeError(
"This method cannot be called from the event loop thread"
)
async def sleep_until_stopped(self) -> None:
"""Sleep until :meth:`stop` is called."""
await self._stop_event.wait()
async def stop(self, cancel_remaining: bool = False) -> None:
"""
Signal the portal to shut down.
This marks the portal as no longer accepting new calls and exits from
:meth:`sleep_until_stopped`.
:param cancel_remaining: ``True`` to cancel all the remaining tasks, ``False``
to let them finish before returning
"""
self._event_loop_thread_id = None
self._stop_event.set()
if cancel_remaining:
self._task_group.cancel_scope.cancel()
async def _call_func(
self,
func: Callable[[Unpack[PosArgsT]], Awaitable[T_Retval] | T_Retval],
args: tuple[Unpack[PosArgsT]],
kwargs: dict[str, Any],
future: Future[T_Retval],
) -> None:
def callback(f: Future[T_Retval]) -> None:
if f.cancelled() and self._event_loop_thread_id not in (
None,
threading.get_ident(),
):
self.call(scope.cancel)
try:
retval_or_awaitable = func(*args, **kwargs)
if isawaitable(retval_or_awaitable):
with CancelScope() as scope:
if future.cancelled():
scope.cancel()
else:
future.add_done_callback(callback)
retval = await retval_or_awaitable
else:
retval = retval_or_awaitable
except self._cancelled_exc_class:
future.cancel()
future.set_running_or_notify_cancel()
except BaseException as exc:
if not future.cancelled():
future.set_exception(exc)
# Let base exceptions fall through
if not isinstance(exc, Exception):
raise
else:
if not future.cancelled():
future.set_result(retval)
finally:
scope = None # type: ignore[assignment]
def _spawn_task_from_thread(
self,
func: Callable[[Unpack[PosArgsT]], Awaitable[T_Retval] | T_Retval],
args: tuple[Unpack[PosArgsT]],
kwargs: dict[str, Any],
name: object,
future: Future[T_Retval],
) -> None:
"""
Spawn a new task using the given callable.
Implementors must ensure that the future is resolved when the task finishes.
:param func: a callable
:param args: positional arguments to be passed to the callable
:param kwargs: keyword arguments to be passed to the callable
:param name: name of the task (will be coerced to a string if not ``None``)
:param future: a future that will resolve to the return value of the callable,
or the exception raised during its execution
"""
raise NotImplementedError
@overload
def call(
self,
func: Callable[[Unpack[PosArgsT]], Awaitable[T_Retval]],
*args: Unpack[PosArgsT],
) -> T_Retval:
...
@overload
def call(
self, func: Callable[[Unpack[PosArgsT]], T_Retval], *args: Unpack[PosArgsT]
) -> T_Retval:
...
def call(
self,
func: Callable[[Unpack[PosArgsT]], Awaitable[T_Retval] | T_Retval],
*args: Unpack[PosArgsT],
) -> T_Retval:
"""
Call the given function in the event loop thread.
If the callable returns a coroutine object, it is awaited on.
:param func: any callable
:raises RuntimeError: if the portal is not running or if this method is called
from within the event loop thread
"""
return cast(T_Retval, self.start_task_soon(func, *args).result())
@overload
def start_task_soon(
self,
func: Callable[[Unpack[PosArgsT]], Awaitable[T_Retval]],
*args: Unpack[PosArgsT],
name: object = None,
) -> Future[T_Retval]:
...
@overload
def start_task_soon(
self,
func: Callable[[Unpack[PosArgsT]], T_Retval],
*args: Unpack[PosArgsT],
name: object = None,
) -> Future[T_Retval]:
...
def start_task_soon(
self,
func: Callable[[Unpack[PosArgsT]], Awaitable[T_Retval] | T_Retval],
*args: Unpack[PosArgsT],
name: object = None,
) -> Future[T_Retval]:
"""
Start a task in the portal's task group.
The task will be run inside a cancel scope which can be cancelled by cancelling
the returned future.
:param func: the target function
:param args: positional arguments passed to ``func``
:param name: name of the task (will be coerced to a string if not ``None``)
:return: a future that resolves with the return value of the callable if the
task completes successfully, or with the exception raised in the task
:raises RuntimeError: if the portal is not running or if this method is called
from within the event loop thread
:rtype: concurrent.futures.Future[T_Retval]
.. versionadded:: 3.0
"""
self._check_running()
f: Future[T_Retval] = Future()
self._spawn_task_from_thread(func, args, {}, name, f)
return f
def start_task(
self,
func: Callable[..., Awaitable[T_Retval]],
*args: object,
name: object = None,
) -> tuple[Future[T_Retval], Any]:
"""
Start a task in the portal's task group and wait until it signals for readiness.
This method works the same way as :meth:`.abc.TaskGroup.start`.
:param func: the target function
:param args: positional arguments passed to ``func``
:param name: name of the task (will be coerced to a string if not ``None``)
:return: a tuple of (future, task_status_value) where the ``task_status_value``
is the value passed to ``task_status.started()`` from within the target
function
:rtype: tuple[concurrent.futures.Future[T_Retval], Any]
.. versionadded:: 3.0
"""
def task_done(future: Future[T_Retval]) -> None:
if not task_status_future.done():
if future.cancelled():
task_status_future.cancel()
elif future.exception():
task_status_future.set_exception(future.exception())
else:
exc = RuntimeError(
"Task exited without calling task_status.started()"
)
task_status_future.set_exception(exc)
self._check_running()
task_status_future: Future = Future()
task_status = _BlockingPortalTaskStatus(task_status_future)
f: Future = Future()
f.add_done_callback(task_done)
self._spawn_task_from_thread(func, args, {"task_status": task_status}, name, f)
return f, task_status_future.result()
def wrap_async_context_manager(
self, cm: AsyncContextManager[T_co]
) -> ContextManager[T_co]:
"""
Wrap an async context manager as a synchronous context manager via this portal.
Spawns a task that will call both ``__aenter__()`` and ``__aexit__()``, stopping
in the middle until the synchronous context manager exits.
:param cm: an asynchronous context manager
:return: a synchronous context manager
.. versionadded:: 2.1
"""
return _BlockingAsyncContextManager(cm, self)
@contextmanager
def start_blocking_portal(
backend: str = "asyncio", backend_options: dict[str, Any] | None = None
) -> Generator[BlockingPortal, Any, None]:
"""
Start a new event loop in a new thread and run a blocking portal in its main task.
The parameters are the same as for :func:`~anyio.run`.
:param backend: name of the backend
:param backend_options: backend options
:return: a context manager that yields a blocking portal
.. versionchanged:: 3.0
Usage as a context manager is now required.
"""
async def run_portal() -> None:
async with BlockingPortal() as portal_:
if future.set_running_or_notify_cancel():
future.set_result(portal_)
await portal_.sleep_until_stopped()
future: Future[BlockingPortal] = Future()
with ThreadPoolExecutor(1) as executor:
run_future = executor.submit(
_eventloop.run, # type: ignore[arg-type]
run_portal,
backend=backend,
backend_options=backend_options,
)
try:
wait(
cast(Iterable[Future], [run_future, future]),
return_when=FIRST_COMPLETED,
)
except BaseException:
future.cancel()
run_future.cancel()
raise
if future.done():
portal = future.result()
cancel_remaining_tasks = False
try:
yield portal
except BaseException:
cancel_remaining_tasks = True
raise
finally:
try:
portal.call(portal.stop, cancel_remaining_tasks)
except RuntimeError:
pass
run_future.result()
def check_cancelled() -> None:
"""
Check if the cancel scope of the host task's running the current worker thread has
been cancelled.
If the host task's current cancel scope has indeed been cancelled, the
backend-specific cancellation exception will be raised.
:raises RuntimeError: if the current thread was not spawned by
:func:`.to_thread.run_sync`
"""
try:
async_backend: AsyncBackend = threadlocals.current_async_backend
except AttributeError:
raise RuntimeError(
"This function can only be run from an AnyIO worker thread"
) from None
async_backend.check_cancelled()
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