mirror of https://github.com/python/cpython
756 lines
23 KiB
Python
756 lines
23 KiB
Python
#
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# Module providing the `Pool` class for managing a process pool
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#
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# multiprocessing/pool.py
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#
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# Copyright (c) 2006-2008, R Oudkerk
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# Licensed to PSF under a Contributor Agreement.
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#
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__all__ = ['Pool']
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#
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# Imports
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#
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import threading
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import queue
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import itertools
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import collections
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import time
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import traceback
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from multiprocessing import Process, cpu_count, TimeoutError
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from multiprocessing.util import Finalize, debug
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#
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# Constants representing the state of a pool
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#
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RUN = 0
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CLOSE = 1
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TERMINATE = 2
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#
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# Miscellaneous
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#
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job_counter = itertools.count()
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def mapstar(args):
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return list(map(*args))
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def starmapstar(args):
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return list(itertools.starmap(args[0], args[1]))
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#
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# Hack to embed stringification of remote traceback in local traceback
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#
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class RemoteTraceback(Exception):
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def __init__(self, tb):
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self.tb = tb
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def __str__(self):
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return self.tb
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class ExceptionWithTraceback:
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def __init__(self, exc, tb):
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tb = traceback.format_exception(type(exc), exc, tb)
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tb = ''.join(tb)
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self.exc = exc
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self.tb = '\n"""\n%s"""' % tb
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def __reduce__(self):
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return rebuild_exc, (self.exc, self.tb)
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def rebuild_exc(exc, tb):
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exc.__cause__ = RemoteTraceback(tb)
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return exc
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#
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# Code run by worker processes
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#
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class MaybeEncodingError(Exception):
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"""Wraps possible unpickleable errors, so they can be
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safely sent through the socket."""
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def __init__(self, exc, value):
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self.exc = repr(exc)
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self.value = repr(value)
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super(MaybeEncodingError, self).__init__(self.exc, self.value)
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def __str__(self):
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return "Error sending result: '%s'. Reason: '%s'" % (self.value,
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self.exc)
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def __repr__(self):
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return "<MaybeEncodingError: %s>" % str(self)
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def worker(inqueue, outqueue, initializer=None, initargs=(), maxtasks=None):
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assert maxtasks is None or (type(maxtasks) == int and maxtasks > 0)
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put = outqueue.put
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get = inqueue.get
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if hasattr(inqueue, '_writer'):
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inqueue._writer.close()
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outqueue._reader.close()
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if initializer is not None:
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initializer(*initargs)
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completed = 0
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while maxtasks is None or (maxtasks and completed < maxtasks):
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try:
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task = get()
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except (EOFError, OSError):
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debug('worker got EOFError or OSError -- exiting')
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break
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if task is None:
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debug('worker got sentinel -- exiting')
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break
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job, i, func, args, kwds = task
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try:
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result = (True, func(*args, **kwds))
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except Exception as e:
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e = ExceptionWithTraceback(e, e.__traceback__)
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result = (False, e)
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try:
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put((job, i, result))
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except Exception as e:
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wrapped = MaybeEncodingError(e, result[1])
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debug("Possible encoding error while sending result: %s" % (
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wrapped))
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put((job, i, (False, wrapped)))
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completed += 1
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debug('worker exiting after %d tasks' % completed)
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#
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# Class representing a process pool
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#
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class Pool(object):
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'''
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Class which supports an async version of applying functions to arguments.
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'''
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Process = Process
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def __init__(self, processes=None, initializer=None, initargs=(),
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maxtasksperchild=None):
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self._setup_queues()
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self._taskqueue = queue.Queue()
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self._cache = {}
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self._state = RUN
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self._maxtasksperchild = maxtasksperchild
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self._initializer = initializer
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self._initargs = initargs
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if processes is None:
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try:
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processes = cpu_count()
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except NotImplementedError:
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processes = 1
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if processes < 1:
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raise ValueError("Number of processes must be at least 1")
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if initializer is not None and not callable(initializer):
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raise TypeError('initializer must be a callable')
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self._processes = processes
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self._pool = []
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self._repopulate_pool()
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self._worker_handler = threading.Thread(
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target=Pool._handle_workers,
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args=(self, )
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)
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self._worker_handler.daemon = True
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self._worker_handler._state = RUN
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self._worker_handler.start()
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self._task_handler = threading.Thread(
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target=Pool._handle_tasks,
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args=(self._taskqueue, self._quick_put, self._outqueue, self._pool)
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)
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self._task_handler.daemon = True
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self._task_handler._state = RUN
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self._task_handler.start()
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self._result_handler = threading.Thread(
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target=Pool._handle_results,
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args=(self._outqueue, self._quick_get, self._cache)
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)
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self._result_handler.daemon = True
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self._result_handler._state = RUN
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self._result_handler.start()
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self._terminate = Finalize(
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self, self._terminate_pool,
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args=(self._taskqueue, self._inqueue, self._outqueue, self._pool,
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self._worker_handler, self._task_handler,
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self._result_handler, self._cache),
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exitpriority=15
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)
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def _join_exited_workers(self):
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"""Cleanup after any worker processes which have exited due to reaching
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their specified lifetime. Returns True if any workers were cleaned up.
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"""
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cleaned = False
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for i in reversed(range(len(self._pool))):
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worker = self._pool[i]
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if worker.exitcode is not None:
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# worker exited
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debug('cleaning up worker %d' % i)
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worker.join()
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cleaned = True
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del self._pool[i]
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return cleaned
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def _repopulate_pool(self):
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"""Bring the number of pool processes up to the specified number,
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for use after reaping workers which have exited.
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"""
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for i in range(self._processes - len(self._pool)):
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w = self.Process(target=worker,
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args=(self._inqueue, self._outqueue,
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self._initializer,
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self._initargs, self._maxtasksperchild)
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)
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self._pool.append(w)
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w.name = w.name.replace('Process', 'PoolWorker')
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w.daemon = True
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w.start()
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debug('added worker')
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def _maintain_pool(self):
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"""Clean up any exited workers and start replacements for them.
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"""
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if self._join_exited_workers():
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self._repopulate_pool()
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def _setup_queues(self):
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from .queues import SimpleQueue
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self._inqueue = SimpleQueue()
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self._outqueue = SimpleQueue()
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self._quick_put = self._inqueue._writer.send
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self._quick_get = self._outqueue._reader.recv
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def apply(self, func, args=(), kwds={}):
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'''
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Equivalent of `func(*args, **kwds)`.
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'''
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assert self._state == RUN
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return self.apply_async(func, args, kwds).get()
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def map(self, func, iterable, chunksize=None):
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'''
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Apply `func` to each element in `iterable`, collecting the results
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in a list that is returned.
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'''
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return self._map_async(func, iterable, mapstar, chunksize).get()
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def starmap(self, func, iterable, chunksize=None):
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'''
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Like `map()` method but the elements of the `iterable` are expected to
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be iterables as well and will be unpacked as arguments. Hence
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`func` and (a, b) becomes func(a, b).
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'''
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return self._map_async(func, iterable, starmapstar, chunksize).get()
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def starmap_async(self, func, iterable, chunksize=None, callback=None,
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error_callback=None):
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'''
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Asynchronous version of `starmap()` method.
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'''
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return self._map_async(func, iterable, starmapstar, chunksize,
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callback, error_callback)
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def imap(self, func, iterable, chunksize=1):
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'''
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Equivalent of `map()` -- can be MUCH slower than `Pool.map()`.
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'''
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if self._state != RUN:
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raise ValueError("Pool not running")
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if chunksize == 1:
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result = IMapIterator(self._cache)
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self._taskqueue.put((((result._job, i, func, (x,), {})
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for i, x in enumerate(iterable)), result._set_length))
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return result
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else:
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assert chunksize > 1
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task_batches = Pool._get_tasks(func, iterable, chunksize)
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result = IMapIterator(self._cache)
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self._taskqueue.put((((result._job, i, mapstar, (x,), {})
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for i, x in enumerate(task_batches)), result._set_length))
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return (item for chunk in result for item in chunk)
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def imap_unordered(self, func, iterable, chunksize=1):
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'''
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Like `imap()` method but ordering of results is arbitrary.
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'''
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if self._state != RUN:
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raise ValueError("Pool not running")
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if chunksize == 1:
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result = IMapUnorderedIterator(self._cache)
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self._taskqueue.put((((result._job, i, func, (x,), {})
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for i, x in enumerate(iterable)), result._set_length))
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return result
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else:
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assert chunksize > 1
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task_batches = Pool._get_tasks(func, iterable, chunksize)
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result = IMapUnorderedIterator(self._cache)
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self._taskqueue.put((((result._job, i, mapstar, (x,), {})
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for i, x in enumerate(task_batches)), result._set_length))
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return (item for chunk in result for item in chunk)
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def apply_async(self, func, args=(), kwds={}, callback=None,
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error_callback=None):
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'''
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Asynchronous version of `apply()` method.
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'''
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if self._state != RUN:
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raise ValueError("Pool not running")
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result = ApplyResult(self._cache, callback, error_callback)
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self._taskqueue.put(([(result._job, None, func, args, kwds)], None))
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return result
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def map_async(self, func, iterable, chunksize=None, callback=None,
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error_callback=None):
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'''
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Asynchronous version of `map()` method.
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'''
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return self._map_async(func, iterable, mapstar, chunksize, callback,
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error_callback)
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def _map_async(self, func, iterable, mapper, chunksize=None, callback=None,
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error_callback=None):
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'''
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Helper function to implement map, starmap and their async counterparts.
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'''
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if self._state != RUN:
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raise ValueError("Pool not running")
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if not hasattr(iterable, '__len__'):
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iterable = list(iterable)
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if chunksize is None:
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chunksize, extra = divmod(len(iterable), len(self._pool) * 4)
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if extra:
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chunksize += 1
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if len(iterable) == 0:
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chunksize = 0
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task_batches = Pool._get_tasks(func, iterable, chunksize)
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result = MapResult(self._cache, chunksize, len(iterable), callback,
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error_callback=error_callback)
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self._taskqueue.put((((result._job, i, mapper, (x,), {})
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for i, x in enumerate(task_batches)), None))
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return result
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@staticmethod
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def _handle_workers(pool):
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thread = threading.current_thread()
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# Keep maintaining workers until the cache gets drained, unless the pool
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# is terminated.
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while thread._state == RUN or (pool._cache and thread._state != TERMINATE):
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pool._maintain_pool()
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time.sleep(0.1)
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# send sentinel to stop workers
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pool._taskqueue.put(None)
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debug('worker handler exiting')
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@staticmethod
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def _handle_tasks(taskqueue, put, outqueue, pool):
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thread = threading.current_thread()
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for taskseq, set_length in iter(taskqueue.get, None):
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i = -1
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for i, task in enumerate(taskseq):
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if thread._state:
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debug('task handler found thread._state != RUN')
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break
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try:
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put(task)
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except OSError:
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debug('could not put task on queue')
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break
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else:
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if set_length:
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debug('doing set_length()')
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set_length(i+1)
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continue
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break
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else:
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debug('task handler got sentinel')
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try:
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# tell result handler to finish when cache is empty
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debug('task handler sending sentinel to result handler')
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outqueue.put(None)
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# tell workers there is no more work
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debug('task handler sending sentinel to workers')
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for p in pool:
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put(None)
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except OSError:
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debug('task handler got OSError when sending sentinels')
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debug('task handler exiting')
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@staticmethod
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def _handle_results(outqueue, get, cache):
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thread = threading.current_thread()
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while 1:
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try:
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task = get()
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except (OSError, EOFError):
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debug('result handler got EOFError/OSError -- exiting')
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return
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if thread._state:
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assert thread._state == TERMINATE
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debug('result handler found thread._state=TERMINATE')
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break
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if task is None:
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debug('result handler got sentinel')
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break
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job, i, obj = task
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try:
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cache[job]._set(i, obj)
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except KeyError:
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pass
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while cache and thread._state != TERMINATE:
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try:
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task = get()
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except (OSError, EOFError):
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debug('result handler got EOFError/OSError -- exiting')
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return
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if task is None:
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debug('result handler ignoring extra sentinel')
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continue
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job, i, obj = task
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try:
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cache[job]._set(i, obj)
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except KeyError:
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pass
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if hasattr(outqueue, '_reader'):
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debug('ensuring that outqueue is not full')
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# If we don't make room available in outqueue then
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# attempts to add the sentinel (None) to outqueue may
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# block. There is guaranteed to be no more than 2 sentinels.
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try:
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for i in range(10):
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if not outqueue._reader.poll():
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break
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get()
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except (OSError, EOFError):
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pass
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debug('result handler exiting: len(cache)=%s, thread._state=%s',
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len(cache), thread._state)
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@staticmethod
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def _get_tasks(func, it, size):
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it = iter(it)
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while 1:
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x = tuple(itertools.islice(it, size))
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if not x:
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return
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yield (func, x)
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def __reduce__(self):
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raise NotImplementedError(
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'pool objects cannot be passed between processes or pickled'
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)
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def close(self):
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debug('closing pool')
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if self._state == RUN:
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self._state = CLOSE
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self._worker_handler._state = CLOSE
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def terminate(self):
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debug('terminating pool')
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self._state = TERMINATE
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self._worker_handler._state = TERMINATE
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self._terminate()
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def join(self):
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debug('joining pool')
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assert self._state in (CLOSE, TERMINATE)
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self._worker_handler.join()
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self._task_handler.join()
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self._result_handler.join()
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for p in self._pool:
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p.join()
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@staticmethod
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def _help_stuff_finish(inqueue, task_handler, size):
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# task_handler may be blocked trying to put items on inqueue
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debug('removing tasks from inqueue until task handler finished')
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inqueue._rlock.acquire()
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while task_handler.is_alive() and inqueue._reader.poll():
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inqueue._reader.recv()
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time.sleep(0)
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@classmethod
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def _terminate_pool(cls, taskqueue, inqueue, outqueue, pool,
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worker_handler, task_handler, result_handler, cache):
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# this is guaranteed to only be called once
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debug('finalizing pool')
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worker_handler._state = TERMINATE
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task_handler._state = TERMINATE
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debug('helping task handler/workers to finish')
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cls._help_stuff_finish(inqueue, task_handler, len(pool))
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assert result_handler.is_alive() or len(cache) == 0
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result_handler._state = TERMINATE
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outqueue.put(None) # sentinel
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# We must wait for the worker handler to exit before terminating
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# workers because we don't want workers to be restarted behind our back.
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debug('joining worker handler')
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if threading.current_thread() is not worker_handler:
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worker_handler.join()
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# Terminate workers which haven't already finished.
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if pool and hasattr(pool[0], 'terminate'):
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debug('terminating workers')
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for p in pool:
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if p.exitcode is None:
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p.terminate()
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debug('joining task handler')
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if threading.current_thread() is not task_handler:
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task_handler.join()
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debug('joining result handler')
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if threading.current_thread() is not result_handler:
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result_handler.join()
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if pool and hasattr(pool[0], 'terminate'):
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debug('joining pool workers')
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for p in pool:
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if p.is_alive():
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# worker has not yet exited
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debug('cleaning up worker %d' % p.pid)
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p.join()
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def __enter__(self):
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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self.terminate()
|
|
|
|
#
|
|
# Class whose instances are returned by `Pool.apply_async()`
|
|
#
|
|
|
|
class ApplyResult(object):
|
|
|
|
def __init__(self, cache, callback, error_callback):
|
|
self._event = threading.Event()
|
|
self._job = next(job_counter)
|
|
self._cache = cache
|
|
self._callback = callback
|
|
self._error_callback = error_callback
|
|
cache[self._job] = self
|
|
|
|
def ready(self):
|
|
return self._event.is_set()
|
|
|
|
def successful(self):
|
|
assert self.ready()
|
|
return self._success
|
|
|
|
def wait(self, timeout=None):
|
|
self._event.wait(timeout)
|
|
|
|
def get(self, timeout=None):
|
|
self.wait(timeout)
|
|
if not self.ready():
|
|
raise TimeoutError
|
|
if self._success:
|
|
return self._value
|
|
else:
|
|
raise self._value
|
|
|
|
def _set(self, i, obj):
|
|
self._success, self._value = obj
|
|
if self._callback and self._success:
|
|
self._callback(self._value)
|
|
if self._error_callback and not self._success:
|
|
self._error_callback(self._value)
|
|
self._event.set()
|
|
del self._cache[self._job]
|
|
|
|
AsyncResult = ApplyResult # create alias -- see #17805
|
|
|
|
#
|
|
# Class whose instances are returned by `Pool.map_async()`
|
|
#
|
|
|
|
class MapResult(ApplyResult):
|
|
|
|
def __init__(self, cache, chunksize, length, callback, error_callback):
|
|
ApplyResult.__init__(self, cache, callback,
|
|
error_callback=error_callback)
|
|
self._success = True
|
|
self._value = [None] * length
|
|
self._chunksize = chunksize
|
|
if chunksize <= 0:
|
|
self._number_left = 0
|
|
self._event.set()
|
|
del cache[self._job]
|
|
else:
|
|
self._number_left = length//chunksize + bool(length % chunksize)
|
|
|
|
def _set(self, i, success_result):
|
|
success, result = success_result
|
|
if success:
|
|
self._value[i*self._chunksize:(i+1)*self._chunksize] = result
|
|
self._number_left -= 1
|
|
if self._number_left == 0:
|
|
if self._callback:
|
|
self._callback(self._value)
|
|
del self._cache[self._job]
|
|
self._event.set()
|
|
else:
|
|
self._success = False
|
|
self._value = result
|
|
if self._error_callback:
|
|
self._error_callback(self._value)
|
|
del self._cache[self._job]
|
|
self._event.set()
|
|
|
|
#
|
|
# Class whose instances are returned by `Pool.imap()`
|
|
#
|
|
|
|
class IMapIterator(object):
|
|
|
|
def __init__(self, cache):
|
|
self._cond = threading.Condition(threading.Lock())
|
|
self._job = next(job_counter)
|
|
self._cache = cache
|
|
self._items = collections.deque()
|
|
self._index = 0
|
|
self._length = None
|
|
self._unsorted = {}
|
|
cache[self._job] = self
|
|
|
|
def __iter__(self):
|
|
return self
|
|
|
|
def next(self, timeout=None):
|
|
self._cond.acquire()
|
|
try:
|
|
try:
|
|
item = self._items.popleft()
|
|
except IndexError:
|
|
if self._index == self._length:
|
|
raise StopIteration
|
|
self._cond.wait(timeout)
|
|
try:
|
|
item = self._items.popleft()
|
|
except IndexError:
|
|
if self._index == self._length:
|
|
raise StopIteration
|
|
raise TimeoutError
|
|
finally:
|
|
self._cond.release()
|
|
|
|
success, value = item
|
|
if success:
|
|
return value
|
|
raise value
|
|
|
|
__next__ = next # XXX
|
|
|
|
def _set(self, i, obj):
|
|
self._cond.acquire()
|
|
try:
|
|
if self._index == i:
|
|
self._items.append(obj)
|
|
self._index += 1
|
|
while self._index in self._unsorted:
|
|
obj = self._unsorted.pop(self._index)
|
|
self._items.append(obj)
|
|
self._index += 1
|
|
self._cond.notify()
|
|
else:
|
|
self._unsorted[i] = obj
|
|
|
|
if self._index == self._length:
|
|
del self._cache[self._job]
|
|
finally:
|
|
self._cond.release()
|
|
|
|
def _set_length(self, length):
|
|
self._cond.acquire()
|
|
try:
|
|
self._length = length
|
|
if self._index == self._length:
|
|
self._cond.notify()
|
|
del self._cache[self._job]
|
|
finally:
|
|
self._cond.release()
|
|
|
|
#
|
|
# Class whose instances are returned by `Pool.imap_unordered()`
|
|
#
|
|
|
|
class IMapUnorderedIterator(IMapIterator):
|
|
|
|
def _set(self, i, obj):
|
|
self._cond.acquire()
|
|
try:
|
|
self._items.append(obj)
|
|
self._index += 1
|
|
self._cond.notify()
|
|
if self._index == self._length:
|
|
del self._cache[self._job]
|
|
finally:
|
|
self._cond.release()
|
|
|
|
#
|
|
#
|
|
#
|
|
|
|
class ThreadPool(Pool):
|
|
|
|
from .dummy import Process
|
|
|
|
def __init__(self, processes=None, initializer=None, initargs=()):
|
|
Pool.__init__(self, processes, initializer, initargs)
|
|
|
|
def _setup_queues(self):
|
|
self._inqueue = queue.Queue()
|
|
self._outqueue = queue.Queue()
|
|
self._quick_put = self._inqueue.put
|
|
self._quick_get = self._outqueue.get
|
|
|
|
@staticmethod
|
|
def _help_stuff_finish(inqueue, task_handler, size):
|
|
# put sentinels at head of inqueue to make workers finish
|
|
inqueue.not_empty.acquire()
|
|
try:
|
|
inqueue.queue.clear()
|
|
inqueue.queue.extend([None] * size)
|
|
inqueue.not_empty.notify_all()
|
|
finally:
|
|
inqueue.not_empty.release()
|