137 lines
4.9 KiB
Python
137 lines
4.9 KiB
Python
""" Multicast DNS Service Discovery for Python, v0.14-wmcbrine
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Copyright 2003 Paul Scott-Murphy, 2014 William McBrine
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This module provides a framework for the use of DNS Service Discovery
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using IP multicast.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
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USA
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"""
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import asyncio
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import concurrent.futures
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import contextlib
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import sys
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from typing import Any, Awaitable, Coroutine, Optional, Set
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if sys.version_info[:2] < (3, 11):
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from async_timeout import timeout as asyncio_timeout
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else:
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from asyncio import timeout as asyncio_timeout
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from .._exceptions import EventLoopBlocked
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from ..const import _LOADED_SYSTEM_TIMEOUT
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from .time import millis_to_seconds
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# The combined timeouts should be lower than _CLOSE_TIMEOUT + _WAIT_FOR_LOOP_TASKS_TIMEOUT
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_TASK_AWAIT_TIMEOUT = 1
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_GET_ALL_TASKS_TIMEOUT = 3
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_WAIT_FOR_LOOP_TASKS_TIMEOUT = 3 # Must be larger than _TASK_AWAIT_TIMEOUT
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def _set_future_none_if_not_done(fut: asyncio.Future) -> None:
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"""Set a future to None if it is not done."""
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if not fut.done(): # pragma: no branch
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fut.set_result(None)
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def _resolve_all_futures_to_none(futures: Set[asyncio.Future]) -> None:
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"""Resolve all futures to None."""
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for fut in futures:
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_set_future_none_if_not_done(fut)
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futures.clear()
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async def wait_for_future_set_or_timeout(
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loop: asyncio.AbstractEventLoop, future_set: Set[asyncio.Future], timeout: float
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) -> None:
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"""Wait for a future or timeout (in milliseconds)."""
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future = loop.create_future()
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future_set.add(future)
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handle = loop.call_later(millis_to_seconds(timeout), _set_future_none_if_not_done, future)
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try:
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await future
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finally:
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handle.cancel()
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future_set.discard(future)
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async def wait_event_or_timeout(event: asyncio.Event, timeout: float) -> None:
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"""Wait for an event or timeout."""
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with contextlib.suppress(asyncio.TimeoutError):
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async with asyncio_timeout(timeout):
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await event.wait()
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async def _async_get_all_tasks(loop: asyncio.AbstractEventLoop) -> Set[asyncio.Task]:
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"""Return all tasks running."""
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await asyncio.sleep(0) # flush out any call_soon_threadsafe
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# If there are multiple event loops running, all_tasks is not
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# safe EVEN WHEN CALLED FROM THE EVENTLOOP
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# under PyPy so we have to try a few times.
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for _ in range(3):
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with contextlib.suppress(RuntimeError):
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return asyncio.all_tasks(loop)
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return set()
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async def _wait_for_loop_tasks(wait_tasks: Set[asyncio.Task]) -> None:
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"""Wait for the event loop thread we started to shutdown."""
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await asyncio.wait(wait_tasks, timeout=_TASK_AWAIT_TIMEOUT)
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async def await_awaitable(aw: Awaitable) -> None:
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"""Wait on an awaitable and the task it returns."""
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task = await aw
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await task
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def run_coro_with_timeout(aw: Coroutine, loop: asyncio.AbstractEventLoop, timeout: float) -> Any:
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"""Run a coroutine with a timeout.
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The timeout should only be used as a safeguard to prevent
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the program from blocking forever. The timeout should
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never be expected to be reached during normal operation.
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While not expected during normal operations, the
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function raises `EventLoopBlocked` if the coroutine takes
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longer to complete than the timeout.
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"""
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try:
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return asyncio.run_coroutine_threadsafe(aw, loop).result(
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millis_to_seconds(timeout) + _LOADED_SYSTEM_TIMEOUT
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)
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except concurrent.futures.TimeoutError as ex:
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raise EventLoopBlocked from ex
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def shutdown_loop(loop: asyncio.AbstractEventLoop) -> None:
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"""Wait for pending tasks and stop an event loop."""
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pending_tasks = set(
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asyncio.run_coroutine_threadsafe(_async_get_all_tasks(loop), loop).result(_GET_ALL_TASKS_TIMEOUT)
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)
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pending_tasks -= {task for task in pending_tasks if task.done()}
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if pending_tasks:
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asyncio.run_coroutine_threadsafe(_wait_for_loop_tasks(pending_tasks), loop).result(
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_WAIT_FOR_LOOP_TASKS_TIMEOUT
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)
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loop.call_soon_threadsafe(loop.stop)
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def get_running_loop() -> Optional[asyncio.AbstractEventLoop]:
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"""Check if an event loop is already running."""
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with contextlib.suppress(RuntimeError):
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return asyncio.get_running_loop()
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return None
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