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v0.8.1
v0.8.1
https://github.com/python/cpython
Tip revision: 74f4bd53e03ded8408bcc2de67cf0f5a4ac5b1a1 authored by Barry Warsaw on 23 February 2012, 15:59:38 UTC
Bump some more copyright years (as per PEP 101), since this is the first
Bump some more copyright years (as per PEP 101), since this is the first
Tip revision: 74f4bd5
queues.py
#
# Module implementing queues
#
# multiprocessing/queues.py
#
# Copyright (c) 2006-2008, R Oudkerk --- see COPYING.txt
#
__all__ = ['Queue', 'SimpleQueue', 'JoinableQueue']
import sys
import os
import threading
import collections
import time
import atexit
import weakref
from Queue import Empty, Full
import _multiprocessing
from multiprocessing import Pipe
from multiprocessing.synchronize import Lock, BoundedSemaphore, Semaphore, Condition
from multiprocessing.util import debug, info, Finalize, register_after_fork
from multiprocessing.forking import assert_spawning
#
# Queue type using a pipe, buffer and thread
#
class Queue(object):
def __init__(self, maxsize=0):
if maxsize <= 0:
maxsize = _multiprocessing.SemLock.SEM_VALUE_MAX
self._maxsize = maxsize
self._reader, self._writer = Pipe(duplex=False)
self._rlock = Lock()
self._opid = os.getpid()
if sys.platform == 'win32':
self._wlock = None
else:
self._wlock = Lock()
self._sem = BoundedSemaphore(maxsize)
self._after_fork()
if sys.platform != 'win32':
register_after_fork(self, Queue._after_fork)
def __getstate__(self):
assert_spawning(self)
return (self._maxsize, self._reader, self._writer,
self._rlock, self._wlock, self._sem, self._opid)
def __setstate__(self, state):
(self._maxsize, self._reader, self._writer,
self._rlock, self._wlock, self._sem, self._opid) = state
self._after_fork()
def _after_fork(self):
debug('Queue._after_fork()')
self._notempty = threading.Condition(threading.Lock())
self._buffer = collections.deque()
self._thread = None
self._jointhread = None
self._joincancelled = False
self._closed = False
self._close = None
self._send = self._writer.send
self._recv = self._reader.recv
self._poll = self._reader.poll
def put(self, obj, block=True, timeout=None):
assert not self._closed
if not self._sem.acquire(block, timeout):
raise Full
self._notempty.acquire()
try:
if self._thread is None:
self._start_thread()
self._buffer.append(obj)
self._notempty.notify()
finally:
self._notempty.release()
def get(self, block=True, timeout=None):
if block and timeout is None:
self._rlock.acquire()
try:
res = self._recv()
self._sem.release()
return res
finally:
self._rlock.release()
else:
if block:
deadline = time.time() + timeout
if not self._rlock.acquire(block, timeout):
raise Empty
try:
if not self._poll(block and (deadline-time.time()) or 0.0):
raise Empty
res = self._recv()
self._sem.release()
return res
finally:
self._rlock.release()
def qsize(self):
# Raises NotImplementedError on Mac OSX because of broken sem_getvalue()
return self._maxsize - self._sem._semlock._get_value()
def empty(self):
return not self._poll()
def full(self):
return self._sem._semlock._is_zero()
def get_nowait(self):
return self.get(False)
def put_nowait(self, obj):
return self.put(obj, False)
def close(self):
self._closed = True
self._reader.close()
if self._close:
self._close()
def join_thread(self):
debug('Queue.join_thread()')
assert self._closed
if self._jointhread:
self._jointhread()
def cancel_join_thread(self):
debug('Queue.cancel_join_thread()')
self._joincancelled = True
try:
self._jointhread.cancel()
except AttributeError:
pass
def _start_thread(self):
debug('Queue._start_thread()')
# Start thread which transfers data from buffer to pipe
self._buffer.clear()
self._thread = threading.Thread(
target=Queue._feed,
args=(self._buffer, self._notempty, self._send,
self._wlock, self._writer.close),
name='QueueFeederThread'
)
self._thread.daemon = True
debug('doing self._thread.start()')
self._thread.start()
debug('... done self._thread.start()')
# On process exit we will wait for data to be flushed to pipe.
#
# However, if this process created the queue then all
# processes which use the queue will be descendants of this
# process. Therefore waiting for the queue to be flushed
# is pointless once all the child processes have been joined.
created_by_this_process = (self._opid == os.getpid())
if not self._joincancelled and not created_by_this_process:
self._jointhread = Finalize(
self._thread, Queue._finalize_join,
[weakref.ref(self._thread)],
exitpriority=-5
)
# Send sentinel to the thread queue object when garbage collected
self._close = Finalize(
self, Queue._finalize_close,
[self._buffer, self._notempty],
exitpriority=10
)
@staticmethod
def _finalize_join(twr):
debug('joining queue thread')
thread = twr()
if thread is not None:
thread.join()
debug('... queue thread joined')
else:
debug('... queue thread already dead')
@staticmethod
def _finalize_close(buffer, notempty):
debug('telling queue thread to quit')
notempty.acquire()
try:
buffer.append(_sentinel)
notempty.notify()
finally:
notempty.release()
@staticmethod
def _feed(buffer, notempty, send, writelock, close):
debug('starting thread to feed data to pipe')
from .util import is_exiting
nacquire = notempty.acquire
nrelease = notempty.release
nwait = notempty.wait
bpopleft = buffer.popleft
sentinel = _sentinel
if sys.platform != 'win32':
wacquire = writelock.acquire
wrelease = writelock.release
else:
wacquire = None
try:
while 1:
nacquire()
try:
if not buffer:
nwait()
finally:
nrelease()
try:
while 1:
obj = bpopleft()
if obj is sentinel:
debug('feeder thread got sentinel -- exiting')
close()
return
if wacquire is None:
send(obj)
else:
wacquire()
try:
send(obj)
finally:
wrelease()
except IndexError:
pass
except Exception, e:
# Since this runs in a daemon thread the resources it uses
# may be become unusable while the process is cleaning up.
# We ignore errors which happen after the process has
# started to cleanup.
try:
if is_exiting():
info('error in queue thread: %s', e)
else:
import traceback
traceback.print_exc()
except Exception:
pass
_sentinel = object()
#
# A queue type which also supports join() and task_done() methods
#
# Note that if you do not call task_done() for each finished task then
# eventually the counter's semaphore may overflow causing Bad Things
# to happen.
#
class JoinableQueue(Queue):
def __init__(self, maxsize=0):
Queue.__init__(self, maxsize)
self._unfinished_tasks = Semaphore(0)
self._cond = Condition()
def __getstate__(self):
return Queue.__getstate__(self) + (self._cond, self._unfinished_tasks)
def __setstate__(self, state):
Queue.__setstate__(self, state[:-2])
self._cond, self._unfinished_tasks = state[-2:]
def put(self, obj, block=True, timeout=None):
assert not self._closed
if not self._sem.acquire(block, timeout):
raise Full
self._notempty.acquire()
self._cond.acquire()
try:
if self._thread is None:
self._start_thread()
self._buffer.append(obj)
self._unfinished_tasks.release()
self._notempty.notify()
finally:
self._cond.release()
self._notempty.release()
def task_done(self):
self._cond.acquire()
try:
if not self._unfinished_tasks.acquire(False):
raise ValueError('task_done() called too many times')
if self._unfinished_tasks._semlock._is_zero():
self._cond.notify_all()
finally:
self._cond.release()
def join(self):
self._cond.acquire()
try:
if not self._unfinished_tasks._semlock._is_zero():
self._cond.wait()
finally:
self._cond.release()
#
# Simplified Queue type -- really just a locked pipe
#
class SimpleQueue(object):
def __init__(self):
self._reader, self._writer = Pipe(duplex=False)
self._rlock = Lock()
if sys.platform == 'win32':
self._wlock = None
else:
self._wlock = Lock()
self._make_methods()
def empty(self):
return not self._reader.poll()
def __getstate__(self):
assert_spawning(self)
return (self._reader, self._writer, self._rlock, self._wlock)
def __setstate__(self, state):
(self._reader, self._writer, self._rlock, self._wlock) = state
self._make_methods()
def _make_methods(self):
recv = self._reader.recv
racquire, rrelease = self._rlock.acquire, self._rlock.release
def get():
racquire()
try:
return recv()
finally:
rrelease()
self.get = get
if self._wlock is None:
# writes to a message oriented win32 pipe are atomic
self.put = self._writer.send
else:
send = self._writer.send
wacquire, wrelease = self._wlock.acquire, self._wlock.release
def put(obj):
wacquire()
try:
return send(obj)
finally:
wrelease()
self.put = put