name : async_helpers.py # Copyright 2019 Canonical, Ltd. # # This program is free software: you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, version 3. # # This program 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 General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program. If not, see <http://www.gnu.org/licenses/>. import asyncio import concurrent.futures import logging log = logging.getLogger("subiquitycore.async_helpers") def _done(fut): try: fut.result() except asyncio.CancelledError: pass def schedule_task(coro, propagate_errors=True): loop = asyncio.get_event_loop() if asyncio.iscoroutine(coro): task = asyncio.Task(coro) else: task = coro if propagate_errors: task.add_done_callback(_done) loop.call_soon(asyncio.ensure_future, task) return task async def run_in_thread(func, *args): loop = asyncio.get_event_loop() try: return await loop.run_in_executor(None, func, *args) except concurrent.futures.CancelledError: raise asyncio.CancelledError class SingleInstanceTask: def __init__(self, func, propagate_errors=True): self.func = func self.propagate_errors = propagate_errors self.task = None async def _start(self, old): if old is not None: old.cancel() try: await old except BaseException: pass schedule_task(self.task, self.propagate_errors) async def start(self, *args, **kw): await self.start_sync(*args, **kw) return self.task def start_sync(self, *args, **kw): old = self.task coro = self.func(*args, **kw) if asyncio.iscoroutine(coro): self.task = asyncio.Task(coro) else: self.task = coro return schedule_task(self._start(old)) async def wait(self): while True: try: return await self.task except asyncio.CancelledError: pass