230 lines
8.2 KiB
Python
230 lines
8.2 KiB
Python
import asyncio
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from datetime import datetime, timezone
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import logging
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class Terminator:
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pass
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class AsyncPool:
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def __init__(self,
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num_workers: int, worker_co,
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name: str, logger: logging.Logger,
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loop: asyncio.AbstractEventLoop = None,
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load_factor: int = 1, max_task_time: int = None,
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return_futures: bool = False, raise_on_join: bool = False
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):
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"""
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This class will create `num_workers` asyncio tasks to work against a queue of
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`num_workers * load_factor` items of back-pressure (IOW we will block after such
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number of items of work is in the queue). `worker_co` will be called
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against each item retrieved from the queue. If any exceptions are raised out of
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worker_co, self.exceptions will be set to True.
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:param loop: asyncio loop to use
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:param num_workers: number of async tasks which will pull from the internal queue
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:param name: name of the worker pool (used for logging)
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:param logger: logger to use
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:param worker_co: async coroutine to call when an item is retrieved from the queue
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:param load_factor: multiplier used for number of items in queue
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:param max_task_time: maximum time allowed for each task before a CancelledError is raised in the task.
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Set to None for no limit.
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:param return_futures: set to reture to return a future for each `push` (imposes CPU overhead)
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:param raise_on_join: raise on join if any exceptions have occurred, default is False
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:return: instance of AsyncWorkerPool
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"""
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self._loop = loop if loop else asyncio.get_event_loop()
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self._num_workers = num_workers
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self._logger = logger if logger else logging.getLogger(__name__)
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self._queue = asyncio.Queue(num_workers * load_factor)
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self._workers: dict[str, asyncio.Future] = {}
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self._exceptions = False
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self._max_task_time = max_task_time
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self._return_futures = return_futures
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self._raise_on_join = raise_on_join
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self._name = name
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self._worker_co = worker_co
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self._status: dict[str, dict | None] = {}
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async def _worker_loop(self, worker_id: str):
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while True:
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got_obj = False
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future = None
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try:
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item = await self._queue.get()
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got_obj = True
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if item.__class__ is Terminator:
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break
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future, args, kwargs = item
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self._status[worker_id] = {
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'started': self._time().isoformat(),
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'data': kwargs.get('entry', {'info': {}}).info.__dict__,
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}
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# the wait_for will cancel the task (task sees CancelledError) and raises a TimeoutError from here
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# so be wary of catching TimeoutErrors in this loop
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result = await asyncio.wait_for(self._worker_co(*args, **kwargs), timeout=self._max_task_time)
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if future:
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future.set_result(result)
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except (KeyboardInterrupt, MemoryError, SystemExit) as e:
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if future:
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future.set_exception(e)
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self._exceptions = True
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raise
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except BaseException as e:
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if isinstance(e, asyncio.exceptions.CancelledError):
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raise e
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self._exceptions = True
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if future:
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# don't log the failure when the client is receiving the future
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future.set_exception(e)
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else:
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self._logger.exception(f'Worker call failed. {str(e)}')
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finally:
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self._status[worker_id] = None
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if got_obj:
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self._queue.task_done()
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@property
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def exceptions(self):
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return self._exceptions
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def has_open_workers(self) -> bool:
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"""
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:return: True if there are open workers.
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"""
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return self.get_available_workers() > 0
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def get_available_workers(self) -> int:
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"""
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:return: number of available workers.
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"""
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return sum(1 for worker_status in self._status.values() if worker_status is None)
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def get_workers_status(self) -> dict[str, datetime | None]:
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"""
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:return: dictionary of worker status.
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"""
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return self._status
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async def __aenter__(self):
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self.start()
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return self
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async def __aexit__(self, exc_type, exc_val, exc_tb):
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await self.join()
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async def push(self, *args, **kwargs) -> asyncio.Future:
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"""
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Method to push work to `worker_co` passed initially to `__init__`.
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:param args: position arguments to be passed to `worker_co`
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:param kwargs: keyword arguments to be passed to `worker_co`
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:return: future of result.
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"""
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future = asyncio.futures.Future(loop=self._loop) if self._return_futures else None
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await self._queue.put((future, args, kwargs))
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self._logger.debug(f"'{self._name}' pool has received a new job. {args} {kwargs}")
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return future
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def start(self):
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""" Will start up worker pool and reset exception state """
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self._exceptions = False
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for worker_number in range(self._num_workers):
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worker_id = f"worker_{worker_number+1}"
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self._createWorker(worker_id)
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async def restart(self, worker_id: str, msg: str = None) -> bool:
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""" Will restart the worker pool """
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if worker_id not in self._workers:
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self._logger.warning(f'Worker {worker_id} does not exist.')
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return False
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try:
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self._workers[worker_id].cancel(msg)
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await self._workers[worker_id]
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except asyncio.exceptions.CancelledError as e:
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self._logger.warning(f'Worker {worker_id} restarted. {str(e)}')
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if worker_id in self._status:
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self._status.pop(worker_id)
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if worker_id in self._workers:
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self._workers.pop(worker_id)
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self._createWorker(worker_id)
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return True
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async def stop(self, worker_id: str, msg: str = None) -> bool:
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""" Will stop the worker """
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if worker_id not in self._workers:
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self._logger.warning(f'Worker {worker_id} does not exist.')
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return False
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if self._workers[worker_id].cancel(msg):
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try:
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await self._workers[worker_id]
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except asyncio.exceptions.CancelledError as e:
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self._logger.warning(f'Worker {worker_id} stopped. {str(e)}')
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if worker_id in self._status:
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self._status.pop(worker_id)
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if worker_id in self._workers:
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self._workers.pop(worker_id)
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return True
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async def join(self) -> None:
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# no-op if workers aren't running
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if len(self._workers) < 1:
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return
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self._logger.info(f'Joining {self._name}')
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# The Terminators will kick each worker from being blocked against the _queue.get() and allow
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# each one to exit.
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for _ in range(self._num_workers):
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await self._queue.put(Terminator())
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try:
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await asyncio.gather(*list(self._workers))
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self._workers = {}
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except:
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self._logger.exception(f'Exception joining {self._name}')
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raise
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finally:
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self._logger.info(f'Completed {self._name}')
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if self._exceptions and self._raise_on_join:
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raise Exception(f"Exception occurred in {self._name} pool")
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def _createWorker(self, worker_id: str) -> asyncio.Future:
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if worker_id in self._workers:
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self._logger.debug(f'Worker {worker_id} already exists.')
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return self._workers[worker_id]
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self._status[worker_id] = None
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self._workers[worker_id] = asyncio.ensure_future(
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coro_or_future=self._worker_loop(worker_id=worker_id),
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loop=self._loop
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)
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self._logger.debug(f'Created {worker_id}')
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return self._workers[worker_id]
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def _time(self) -> datetime:
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return datetime.now(tz=timezone.utc)
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