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* bpo-30414: multiprocesing.Queue._feed do not break from main loop on exc Queue background running thread was not handling exceptions correctly. Any exception occurred inside thread (putting unpickable object) cause feeder to finish running. After that every message put into queue is silently ignored. * bpo-30414: multiprocesing.Queue._feed do not break from main loop on exc Queue background running thread was not handling exceptions correctly. Any exception occurred inside thread (putting unpickable object) cause feeder to finish running. After that every message put into queue is silently ignored.
354 lines
11 KiB
Python
354 lines
11 KiB
Python
#
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# Module implementing queues
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#
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# multiprocessing/queues.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__ = ['Queue', 'SimpleQueue', 'JoinableQueue']
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import sys
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import os
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import threading
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import collections
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import time
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import weakref
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import errno
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from queue import Empty, Full
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import _multiprocessing
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from . import connection
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from . import context
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_ForkingPickler = context.reduction.ForkingPickler
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from .util import debug, info, Finalize, register_after_fork, is_exiting
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#
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# Queue type using a pipe, buffer and thread
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#
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class Queue(object):
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def __init__(self, maxsize=0, *, ctx):
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if maxsize <= 0:
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# Can raise ImportError (see issues #3770 and #23400)
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from .synchronize import SEM_VALUE_MAX as maxsize
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self._maxsize = maxsize
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self._reader, self._writer = connection.Pipe(duplex=False)
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self._rlock = ctx.Lock()
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self._opid = os.getpid()
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if sys.platform == 'win32':
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self._wlock = None
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else:
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self._wlock = ctx.Lock()
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self._sem = ctx.BoundedSemaphore(maxsize)
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# For use by concurrent.futures
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self._ignore_epipe = False
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self._after_fork()
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if sys.platform != 'win32':
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register_after_fork(self, Queue._after_fork)
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def __getstate__(self):
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context.assert_spawning(self)
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return (self._ignore_epipe, self._maxsize, self._reader, self._writer,
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self._rlock, self._wlock, self._sem, self._opid)
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def __setstate__(self, state):
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(self._ignore_epipe, self._maxsize, self._reader, self._writer,
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self._rlock, self._wlock, self._sem, self._opid) = state
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self._after_fork()
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def _after_fork(self):
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debug('Queue._after_fork()')
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self._notempty = threading.Condition(threading.Lock())
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self._buffer = collections.deque()
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self._thread = None
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self._jointhread = None
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self._joincancelled = False
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self._closed = False
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self._close = None
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self._send_bytes = self._writer.send_bytes
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self._recv_bytes = self._reader.recv_bytes
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self._poll = self._reader.poll
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def put(self, obj, block=True, timeout=None):
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assert not self._closed
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if not self._sem.acquire(block, timeout):
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raise Full
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with self._notempty:
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if self._thread is None:
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self._start_thread()
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self._buffer.append(obj)
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self._notempty.notify()
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def get(self, block=True, timeout=None):
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if block and timeout is None:
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with self._rlock:
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res = self._recv_bytes()
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self._sem.release()
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else:
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if block:
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deadline = time.time() + timeout
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if not self._rlock.acquire(block, timeout):
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raise Empty
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try:
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if block:
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timeout = deadline - time.time()
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if timeout < 0 or not self._poll(timeout):
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raise Empty
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elif not self._poll():
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raise Empty
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res = self._recv_bytes()
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self._sem.release()
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finally:
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self._rlock.release()
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# unserialize the data after having released the lock
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return _ForkingPickler.loads(res)
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def qsize(self):
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# Raises NotImplementedError on Mac OSX because of broken sem_getvalue()
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return self._maxsize - self._sem._semlock._get_value()
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def empty(self):
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return not self._poll()
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def full(self):
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return self._sem._semlock._is_zero()
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def get_nowait(self):
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return self.get(False)
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def put_nowait(self, obj):
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return self.put(obj, False)
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def close(self):
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self._closed = True
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try:
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self._reader.close()
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finally:
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close = self._close
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if close:
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self._close = None
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close()
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def join_thread(self):
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debug('Queue.join_thread()')
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assert self._closed
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if self._jointhread:
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self._jointhread()
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def cancel_join_thread(self):
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debug('Queue.cancel_join_thread()')
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self._joincancelled = True
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try:
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self._jointhread.cancel()
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except AttributeError:
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pass
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def _start_thread(self):
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debug('Queue._start_thread()')
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# Start thread which transfers data from buffer to pipe
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self._buffer.clear()
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self._thread = threading.Thread(
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target=Queue._feed,
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args=(self._buffer, self._notempty, self._send_bytes,
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self._wlock, self._writer.close, self._ignore_epipe),
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name='QueueFeederThread'
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)
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self._thread.daemon = True
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debug('doing self._thread.start()')
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self._thread.start()
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debug('... done self._thread.start()')
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# On process exit we will wait for data to be flushed to pipe.
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#
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# However, if this process created the queue then all
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# processes which use the queue will be descendants of this
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# process. Therefore waiting for the queue to be flushed
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# is pointless once all the child processes have been joined.
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created_by_this_process = (self._opid == os.getpid())
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if not self._joincancelled and not created_by_this_process:
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self._jointhread = Finalize(
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self._thread, Queue._finalize_join,
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[weakref.ref(self._thread)],
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exitpriority=-5
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)
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# Send sentinel to the thread queue object when garbage collected
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self._close = Finalize(
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self, Queue._finalize_close,
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[self._buffer, self._notempty],
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exitpriority=10
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)
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@staticmethod
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def _finalize_join(twr):
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debug('joining queue thread')
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thread = twr()
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if thread is not None:
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thread.join()
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debug('... queue thread joined')
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else:
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debug('... queue thread already dead')
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@staticmethod
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def _finalize_close(buffer, notempty):
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debug('telling queue thread to quit')
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with notempty:
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buffer.append(_sentinel)
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notempty.notify()
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@staticmethod
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def _feed(buffer, notempty, send_bytes, writelock, close, ignore_epipe):
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debug('starting thread to feed data to pipe')
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nacquire = notempty.acquire
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nrelease = notempty.release
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nwait = notempty.wait
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bpopleft = buffer.popleft
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sentinel = _sentinel
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if sys.platform != 'win32':
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wacquire = writelock.acquire
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wrelease = writelock.release
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else:
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wacquire = None
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while 1:
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try:
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nacquire()
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try:
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if not buffer:
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nwait()
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finally:
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nrelease()
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try:
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while 1:
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obj = bpopleft()
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if obj is sentinel:
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debug('feeder thread got sentinel -- exiting')
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close()
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return
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# serialize the data before acquiring the lock
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obj = _ForkingPickler.dumps(obj)
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if wacquire is None:
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send_bytes(obj)
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else:
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wacquire()
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try:
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send_bytes(obj)
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finally:
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wrelease()
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except IndexError:
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pass
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except Exception as e:
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if ignore_epipe and getattr(e, 'errno', 0) == errno.EPIPE:
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return
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# Since this runs in a daemon thread the resources it uses
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# may be become unusable while the process is cleaning up.
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# We ignore errors which happen after the process has
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# started to cleanup.
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if is_exiting():
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info('error in queue thread: %s', e)
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return
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else:
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import traceback
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traceback.print_exc()
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_sentinel = object()
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#
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# A queue type which also supports join() and task_done() methods
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#
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# Note that if you do not call task_done() for each finished task then
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# eventually the counter's semaphore may overflow causing Bad Things
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# to happen.
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#
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class JoinableQueue(Queue):
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def __init__(self, maxsize=0, *, ctx):
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Queue.__init__(self, maxsize, ctx=ctx)
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self._unfinished_tasks = ctx.Semaphore(0)
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self._cond = ctx.Condition()
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def __getstate__(self):
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return Queue.__getstate__(self) + (self._cond, self._unfinished_tasks)
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def __setstate__(self, state):
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Queue.__setstate__(self, state[:-2])
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self._cond, self._unfinished_tasks = state[-2:]
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def put(self, obj, block=True, timeout=None):
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assert not self._closed
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if not self._sem.acquire(block, timeout):
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raise Full
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with self._notempty, self._cond:
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if self._thread is None:
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self._start_thread()
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self._buffer.append(obj)
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self._unfinished_tasks.release()
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self._notempty.notify()
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def task_done(self):
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with self._cond:
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if not self._unfinished_tasks.acquire(False):
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raise ValueError('task_done() called too many times')
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if self._unfinished_tasks._semlock._is_zero():
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self._cond.notify_all()
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def join(self):
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with self._cond:
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if not self._unfinished_tasks._semlock._is_zero():
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self._cond.wait()
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#
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# Simplified Queue type -- really just a locked pipe
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#
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class SimpleQueue(object):
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def __init__(self, *, ctx):
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self._reader, self._writer = connection.Pipe(duplex=False)
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self._rlock = ctx.Lock()
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self._poll = self._reader.poll
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if sys.platform == 'win32':
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self._wlock = None
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else:
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self._wlock = ctx.Lock()
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def empty(self):
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return not self._poll()
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def __getstate__(self):
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context.assert_spawning(self)
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return (self._reader, self._writer, self._rlock, self._wlock)
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def __setstate__(self, state):
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(self._reader, self._writer, self._rlock, self._wlock) = state
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self._poll = self._reader.poll
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def get(self):
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with self._rlock:
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res = self._reader.recv_bytes()
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# unserialize the data after having released the lock
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return _ForkingPickler.loads(res)
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def put(self, obj):
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# serialize the data before acquiring the lock
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obj = _ForkingPickler.dumps(obj)
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if self._wlock is None:
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# writes to a message oriented win32 pipe are atomic
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self._writer.send_bytes(obj)
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else:
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with self._wlock:
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self._writer.send_bytes(obj)
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