77 lines
2.2 KiB
Python
77 lines
2.2 KiB
Python
from multiprocessing import Process, Queue
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from collections import namedtuple
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import logging
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import multiprocessing
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import time
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import sys
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import traceback
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logger = multiprocessing.log_to_stderr()
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logger.setLevel(logging.INFO)
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class QueueProcess(object):
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""" Helper class which invokes a worker in a process to produce
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data for one (or more) queues.
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"""
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def __init__(self, get_producer, chunk_size, max_size, args, finished=None):
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self._get_producer = get_producer
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self._queues = []
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self._chunk_size = chunk_size
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self._max_size = max_size
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self._args = args or []
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self._finished = finished
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def create_queue(self):
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""" Adds a multiprocessing queue to the list of queues. Any queues added
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will have the data produced appended.
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"""
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queue = Queue(self._max_size / self._chunk_size)
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self._queues.append(queue)
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return queue
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@staticmethod
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def run_process(target, args, finished=None):
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def _target(tar, arg, fin):
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try:
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tar(*args)
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finally:
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if fin:
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fin()
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Process(target=_target, args=(target, args, finished)).start()
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def run(self):
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# Important! gipc is used here because normal multiprocessing does not work
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# correctly with gevent when we sleep.
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args = (self._get_producer, self._queues, self._chunk_size, self._args)
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QueueProcess.run_process(_run, args, finished=self._finished)
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QueueResult = namedtuple('QueueResult', ['data', 'exception'])
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def _run(get_producer, queues, chunk_size, args):
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producer = get_producer(*args)
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while True:
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try:
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result = QueueResult(producer(chunk_size) or None, None)
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except Exception as ex:
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message = '%s\n%s' % (ex.message, "".join(traceback.format_exception(*sys.exc_info())))
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result = QueueResult(None, Exception(message))
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for queue in queues:
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try:
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queue.put(result, block=True)
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except Exception as ex:
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logger.exception('Exception writing to queue.')
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return
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# Terminate the producer loop if the data produced is empty or an exception occurred.
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if result.data is None or result.exception is not None:
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break
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# Important! This allows the thread that writes the queue data to the pipe
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# to do so. Otherwise, this hangs.
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time.sleep(0)
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