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# This file is part of Pebble.
# Copyright (c) 2013-2025, Matteo Cafasso
# Pebble 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 3 of the License, or (at your option) any later version.
# Pebble 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 Pebble. If not, see <http://www.gnu.org/licenses/>.
import time
import multiprocessing
from itertools import count
from typing import Callable
from concurrent.futures import Future
from pebble.common import ResultStatus, execute, launch_thread, CONSTS
from pebble.pool.base_pool import iter_chunks, run_initializer
from pebble.pool.base_pool import PoolStatus, MapFuture, map_results
from pebble.pool.base_pool import PoolContext, BasePool, Task, TaskPayload
class ThreadPool(BasePool):
"""Allows to schedule jobs within a Pool of Threads.
max_workers is an integer representing the amount of desired process workers
managed by the pool.
If max_tasks is a number greater than zero,
each worker will be restarted after performing an equal amount of tasks.
initializer must be callable, if passed, it will be called
every time a worker is started, receiving initargs as arguments.
"""
def __init__(self, max_workers: int = multiprocessing.cpu_count(),
max_tasks: int = 0,
initializer: Callable = None,
initargs: list = ()):
super().__init__(max_workers, max_tasks, initializer, initargs)
self._pool_manager = PoolManager(self._context)
self._pool_manager_loop = None
def _start_pool(self):
with self._context.status_mutex:
if self._context.status == PoolStatus.CREATED:
self._pool_manager.start()
self._pool_manager_loop = launch_thread(
None, pool_manager_loop, True, self._pool_manager)
self._context.status = PoolStatus.RUNNING
def _stop_pool(self):
if self._pool_manager_loop is not None:
self._pool_manager_loop.join()
self._pool_manager.stop()
def schedule(self, function, args=(), kwargs={}) -> Future:
"""Schedules *function* to be run the Pool.
*args* and *kwargs* will be forwareded to the scheduled function
respectively as arguments and keyword arguments.
A *concurrent.futures.Future* object is returned.
"""
self._check_pool_status()
future = Future()
payload = TaskPayload(function, args, kwargs)
task = Task(next(self._task_counter), future, None, payload)
self._context.task_queue.put(task)
return future
def submit(self, function: Callable, *args, **kwargs) -> Future:
"""This function is provided for compatibility with
`asyncio.loop.run_in_executor`.
For scheduling jobs within the pool use `schedule` instead.
"""
return self.schedule(function, args=args, kwargs=kwargs)
def map(self, function: Callable, *iterables, **kwargs) -> MapFuture:
"""Returns an iterator equivalent to map(function, iterables).
*chunksize* controls the size of the chunks the iterable will
be broken into before being passed to the function. If None
the size will be controlled by the Pool.
"""
self._check_pool_status()
timeout = kwargs.get('timeout')
chunksize = kwargs.get('chunksize', 1)
if chunksize < 1:
raise ValueError("chunksize must be >= 1")
futures = [self.schedule(process_chunk, args=(function, chunk))
for chunk in iter_chunks(zip(*iterables), chunksize)]
return map_results(MapFuture(futures), timeout)
def pool_manager_loop(pool_manager: 'PoolManager'):
context = pool_manager.context
while context.alive:
pool_manager.update_status()
time.sleep(CONSTS.sleep_unit)
class PoolManager:
def __init__(self, context: PoolContext):
self.workers = []
self.context = context
def start(self):
self.create_workers()
def stop(self):
for worker in self.workers:
self.context.task_queue.put(None)
for worker in tuple(self.workers):
self.join_worker(worker)
def update_status(self):
expired = self.inspect_workers()
for worker in expired:
self.join_worker(worker)
self.create_workers()
def inspect_workers(self) -> tuple:
return tuple(w for w in self.workers if not w.is_alive())
def create_workers(self):
for _ in range(self.context.workers - len(self.workers)):
worker = launch_thread(None, worker_thread, True, self.context)
self.workers.append(worker)
def join_worker(self, worker):
worker.join()
self.workers.remove(worker)
def worker_thread(context: PoolContext):
"""The worker thread routines."""
queue = context.task_queue
parameters = context.worker_parameters
if parameters.initializer is not None:
if not run_initializer(parameters.initializer, parameters.initargs):
context.status = PoolStatus.ERROR
return
for task in get_next_task(context, parameters.max_tasks):
execute_next_task(task)
queue.task_done()
def get_next_task(context: PoolContext, max_tasks: int):
counter = count()
queue = context.task_queue
while context.alive and (max_tasks == 0 or next(counter) < max_tasks):
task = queue.get()
if task is not None:
if task.future.cancelled():
task.set_running_or_notify_cancel()
queue.task_done()
else:
yield task
def execute_next_task(task: Task):
payload = task.payload
task.timestamp = time.time()
task.set_running_or_notify_cancel()
result = execute(payload.function, *payload.args, **payload.kwargs)
if result.status == ResultStatus.SUCCESS:
task.future.set_result(result.value)
else:
task.future.set_exception(result.value)
def process_chunk(function: Callable, chunk: list) -> list:
"""Processes a chunk of the iterable passed to map dealing with errors."""
return [execute(function, *args) for args in chunk]
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