Current File : //lib/python3/dist-packages/zeroconf/_utils/asyncio.py
""" Multicast DNS Service Discovery for Python, v0.14-wmcbrine
Copyright 2003 Paul Scott-Murphy, 2014 William McBrine
This module provides a framework for the use of DNS Service Discovery
using IP multicast.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
USA
"""
import asyncio
import concurrent.futures
import contextlib
from typing import Any, Awaitable, Coroutine, Optional, Set
from .time import millis_to_seconds
from .._exceptions import EventLoopBlocked
from ..const import _LOADED_SYSTEM_TIMEOUT
# The combined timeouts should be lower than _CLOSE_TIMEOUT + _WAIT_FOR_LOOP_TASKS_TIMEOUT
_TASK_AWAIT_TIMEOUT = 1
_GET_ALL_TASKS_TIMEOUT = 3
_WAIT_FOR_LOOP_TASKS_TIMEOUT = 3 # Must be larger than _TASK_AWAIT_TIMEOUT
# Switch to asyncio.wait_for once https://bugs.python.org/issue39032 is fixed
async def wait_event_or_timeout(event: asyncio.Event, timeout: float) -> None:
"""Wait for an event or timeout."""
loop = asyncio.get_event_loop()
future = loop.create_future()
def _handle_timeout_or_wait_complete(*_: Any) -> None:
if not future.done():
future.set_result(None)
timer_handle = loop.call_later(timeout, _handle_timeout_or_wait_complete)
event_wait = loop.create_task(event.wait())
event_wait.add_done_callback(_handle_timeout_or_wait_complete)
try:
await future
finally:
timer_handle.cancel()
if not event_wait.done():
event_wait.cancel()
with contextlib.suppress(asyncio.CancelledError):
await event_wait
async def _async_get_all_tasks(loop: asyncio.AbstractEventLoop) -> Set[asyncio.Task]:
"""Return all tasks running."""
await asyncio.sleep(0) # flush out any call_soon_threadsafe
# If there are multiple event loops running, all_tasks is not
# safe EVEN WHEN CALLED FROM THE EVENTLOOP
# under PyPy so we have to try a few times.
for _ in range(3):
with contextlib.suppress(RuntimeError):
return asyncio.all_tasks(loop)
return set()
async def _wait_for_loop_tasks(wait_tasks: Set[asyncio.Task]) -> None:
"""Wait for the event loop thread we started to shutdown."""
await asyncio.wait(wait_tasks, timeout=_TASK_AWAIT_TIMEOUT)
async def await_awaitable(aw: Awaitable) -> None:
"""Wait on an awaitable and the task it returns."""
task = await aw
await task
def run_coro_with_timeout(aw: Coroutine, loop: asyncio.AbstractEventLoop, timeout: float) -> Any:
"""Run a coroutine with a timeout.
The timeout should only be used as a safeguard to prevent
the program from blocking forever. The timeout should
never be expected to be reached during normal operation.
While not expected during normal operations, the
function raises `EventLoopBlocked` if the coroutine takes
longer to complete than the timeout.
"""
try:
return asyncio.run_coroutine_threadsafe(aw, loop).result(
millis_to_seconds(timeout) + _LOADED_SYSTEM_TIMEOUT
)
except concurrent.futures.TimeoutError as ex:
raise EventLoopBlocked from ex
def shutdown_loop(loop: asyncio.AbstractEventLoop) -> None:
"""Wait for pending tasks and stop an event loop."""
pending_tasks = set(
asyncio.run_coroutine_threadsafe(_async_get_all_tasks(loop), loop).result(_GET_ALL_TASKS_TIMEOUT)
)
pending_tasks -= {task for task in pending_tasks if task.done()}
if pending_tasks:
asyncio.run_coroutine_threadsafe(_wait_for_loop_tasks(pending_tasks), loop).result(
_WAIT_FOR_LOOP_TASKS_TIMEOUT
)
loop.call_soon_threadsafe(loop.stop)
# Remove the call to _get_running_loop once we drop python 3.6 support
def get_running_loop() -> Optional[asyncio.AbstractEventLoop]:
"""Check if an event loop is already running."""
with contextlib.suppress(RuntimeError):
return asyncio.get_running_loop()
return None
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