# WorQ - Python task queue
#
# Copyright (c) 2012 Daniel Miller
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
import logging
from threading import Event, Thread
from uuid import uuid4
from worq.task import TaskSpace
log = logging.getLogger(__name__)
[docs]class WorkerPool(object):
"""Multi-thread worker pool
:param broker: Queue broker instance.
:param workers: Number of workers in the pool.
:param thread_factory: A factory function that creates a new thread
object. This should have the same signature as
``threading.Thread`` and should return a thread object.
"""
def __init__(self, broker, workers=1, thread_factory=Thread):
self.broker = broker
self.workers = workers
self.thread_factory = thread_factory
self.threads = []
self.stop_event = Event()
ts = TaskSpace(__name__)
ts.task(lambda:None, 'noop')
broker.expose(ts, replace=True)
[docs] def start(self, timeout=1):
"""Start worker threads.
:param timeout: The number of seconds to wait for a task before
checking if the pool has been asked to stop.
"""
self.stop_event.clear()
for ident in range(self.workers):
args = (ident, self.broker, timeout, self.stop_event)
thread = self.thread_factory(target=worker, args=args)
thread.start()
self.threads.append(thread)
[docs] def stop(self, use_sentinel=False, join=True):
"""Stop the worker pool
:param use_sentinel: Enqueue a no-op task for each worker if true.
This will result in a more responsive shutdown if there are no
other worker pools consuming tasks from the broker.
:param join: Join each thread afer sending the stop signal.
"""
if self.stop_event.is_set():
return
self.stop_event.set()
if use_sentinel:
q = self.broker.queue(__name__)
for thread in self.threads:
if thread.is_alive():
q.noop()
if join:
self.join()
[docs] def join(self):
"""Wait for all threads to stop (call ``stop(join=False)`` first)"""
for thread in self.threads:
thread.join()
def worker(ident, broker, timeout, stop_event):
try:
while not stop_event.is_set():
task = broker.next_task(timeout=timeout)
if task is not None:
broker.invoke(task)
except:
log.error('worker %s crashed', ident, exc_info=True)