1#
2# Module implementing queues
3#
4# multiprocessing/queues.py
5#
6# Copyright (c) 2006-2008, R Oudkerk
7# All rights reserved.
8#
9# Redistribution and use in source and binary forms, with or without
10# modification, are permitted provided that the following conditions
11# are met:
12#
13# 1. Redistributions of source code must retain the above copyright
14#    notice, this list of conditions and the following disclaimer.
15# 2. Redistributions in binary form must reproduce the above copyright
16#    notice, this list of conditions and the following disclaimer in the
17#    documentation and/or other materials provided with the distribution.
18# 3. Neither the name of author nor the names of any contributors may be
19#    used to endorse or promote products derived from this software
20#    without specific prior written permission.
21#
22# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
23# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
26# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32# SUCH DAMAGE.
33#
34
35__all__ = ['Queue', 'SimpleQueue', 'JoinableQueue']
36
37import sys
38import os
39import threading
40import collections
41import time
42import atexit
43import weakref
44
45from Queue import Empty, Full
46import _multiprocessing
47from multiprocessing import Pipe
48from multiprocessing.synchronize import Lock, BoundedSemaphore, Semaphore, Condition
49from multiprocessing.util import debug, info, Finalize, register_after_fork
50from multiprocessing.forking import assert_spawning
51
52#
53# Queue type using a pipe, buffer and thread
54#
55
56class Queue(object):
57
58    def __init__(self, maxsize=0):
59        if maxsize <= 0:
60            maxsize = _multiprocessing.SemLock.SEM_VALUE_MAX
61        self._maxsize = maxsize
62        self._reader, self._writer = Pipe(duplex=False)
63        self._rlock = Lock()
64        self._opid = os.getpid()
65        if sys.platform == 'win32':
66            self._wlock = None
67        else:
68            self._wlock = Lock()
69        self._sem = BoundedSemaphore(maxsize)
70
71        self._after_fork()
72
73        if sys.platform != 'win32':
74            register_after_fork(self, Queue._after_fork)
75
76    def __getstate__(self):
77        assert_spawning(self)
78        return (self._maxsize, self._reader, self._writer,
79                self._rlock, self._wlock, self._sem, self._opid)
80
81    def __setstate__(self, state):
82        (self._maxsize, self._reader, self._writer,
83         self._rlock, self._wlock, self._sem, self._opid) = state
84        self._after_fork()
85
86    def _after_fork(self):
87        debug('Queue._after_fork()')
88        self._notempty = threading.Condition(threading.Lock())
89        self._buffer = collections.deque()
90        self._thread = None
91        self._jointhread = None
92        self._joincancelled = False
93        self._closed = False
94        self._close = None
95        self._send = self._writer.send
96        self._recv = self._reader.recv
97        self._poll = self._reader.poll
98
99    def put(self, obj, block=True, timeout=None):
100        assert not self._closed
101        if not self._sem.acquire(block, timeout):
102            raise Full
103
104        self._notempty.acquire()
105        try:
106            if self._thread is None:
107                self._start_thread()
108            self._buffer.append(obj)
109            self._notempty.notify()
110        finally:
111            self._notempty.release()
112
113    def get(self, block=True, timeout=None):
114        if block and timeout is None:
115            self._rlock.acquire()
116            try:
117                res = self._recv()
118                self._sem.release()
119                return res
120            finally:
121                self._rlock.release()
122
123        else:
124            if block:
125                deadline = time.time() + timeout
126            if not self._rlock.acquire(block, timeout):
127                raise Empty
128            try:
129                if block:
130                    timeout = deadline - time.time()
131                    if timeout < 0 or not self._poll(timeout):
132                        raise Empty
133                elif not self._poll():
134                    raise Empty
135                res = self._recv()
136                self._sem.release()
137                return res
138            finally:
139                self._rlock.release()
140
141    def qsize(self):
142        # Raises NotImplementedError on Mac OSX because of broken sem_getvalue()
143        return self._maxsize - self._sem._semlock._get_value()
144
145    def empty(self):
146        return not self._poll()
147
148    def full(self):
149        return self._sem._semlock._is_zero()
150
151    def get_nowait(self):
152        return self.get(False)
153
154    def put_nowait(self, obj):
155        return self.put(obj, False)
156
157    def close(self):
158        self._closed = True
159        self._reader.close()
160        if self._close:
161            self._close()
162
163    def join_thread(self):
164        debug('Queue.join_thread()')
165        assert self._closed
166        if self._jointhread:
167            self._jointhread()
168
169    def cancel_join_thread(self):
170        debug('Queue.cancel_join_thread()')
171        self._joincancelled = True
172        try:
173            self._jointhread.cancel()
174        except AttributeError:
175            pass
176
177    def _start_thread(self):
178        debug('Queue._start_thread()')
179
180        # Start thread which transfers data from buffer to pipe
181        self._buffer.clear()
182        self._thread = threading.Thread(
183            target=Queue._feed,
184            args=(self._buffer, self._notempty, self._send,
185                  self._wlock, self._writer.close),
186            name='QueueFeederThread'
187            )
188        self._thread.daemon = True
189
190        debug('doing self._thread.start()')
191        self._thread.start()
192        debug('... done self._thread.start()')
193
194        # On process exit we will wait for data to be flushed to pipe.
195        if not self._joincancelled:
196            self._jointhread = Finalize(
197                self._thread, Queue._finalize_join,
198                [weakref.ref(self._thread)],
199                exitpriority=-5
200                )
201
202        # Send sentinel to the thread queue object when garbage collected
203        self._close = Finalize(
204            self, Queue._finalize_close,
205            [self._buffer, self._notempty],
206            exitpriority=10
207            )
208
209    @staticmethod
210    def _finalize_join(twr):
211        debug('joining queue thread')
212        thread = twr()
213        if thread is not None:
214            thread.join()
215            debug('... queue thread joined')
216        else:
217            debug('... queue thread already dead')
218
219    @staticmethod
220    def _finalize_close(buffer, notempty):
221        debug('telling queue thread to quit')
222        notempty.acquire()
223        try:
224            buffer.append(_sentinel)
225            notempty.notify()
226        finally:
227            notempty.release()
228
229    @staticmethod
230    def _feed(buffer, notempty, send, writelock, close):
231        debug('starting thread to feed data to pipe')
232        from .util import is_exiting
233
234        nacquire = notempty.acquire
235        nrelease = notempty.release
236        nwait = notempty.wait
237        bpopleft = buffer.popleft
238        sentinel = _sentinel
239        if sys.platform != 'win32':
240            wacquire = writelock.acquire
241            wrelease = writelock.release
242        else:
243            wacquire = None
244
245        try:
246            while 1:
247                nacquire()
248                try:
249                    if not buffer:
250                        nwait()
251                finally:
252                    nrelease()
253                try:
254                    while 1:
255                        obj = bpopleft()
256                        if obj is sentinel:
257                            debug('feeder thread got sentinel -- exiting')
258                            close()
259                            return
260
261                        if wacquire is None:
262                            send(obj)
263                        else:
264                            wacquire()
265                            try:
266                                send(obj)
267                            finally:
268                                wrelease()
269                except IndexError:
270                    pass
271        except Exception, e:
272            # Since this runs in a daemon thread the resources it uses
273            # may be become unusable while the process is cleaning up.
274            # We ignore errors which happen after the process has
275            # started to cleanup.
276            try:
277                if is_exiting():
278                    info('error in queue thread: %s', e)
279                else:
280                    import traceback
281                    traceback.print_exc()
282            except Exception:
283                pass
284
285_sentinel = object()
286
287#
288# A queue type which also supports join() and task_done() methods
289#
290# Note that if you do not call task_done() for each finished task then
291# eventually the counter's semaphore may overflow causing Bad Things
292# to happen.
293#
294
295class JoinableQueue(Queue):
296
297    def __init__(self, maxsize=0):
298        Queue.__init__(self, maxsize)
299        self._unfinished_tasks = Semaphore(0)
300        self._cond = Condition()
301
302    def __getstate__(self):
303        return Queue.__getstate__(self) + (self._cond, self._unfinished_tasks)
304
305    def __setstate__(self, state):
306        Queue.__setstate__(self, state[:-2])
307        self._cond, self._unfinished_tasks = state[-2:]
308
309    def put(self, obj, block=True, timeout=None):
310        assert not self._closed
311        if not self._sem.acquire(block, timeout):
312            raise Full
313
314        self._notempty.acquire()
315        self._cond.acquire()
316        try:
317            if self._thread is None:
318                self._start_thread()
319            self._buffer.append(obj)
320            self._unfinished_tasks.release()
321            self._notempty.notify()
322        finally:
323            self._cond.release()
324            self._notempty.release()
325
326    def task_done(self):
327        self._cond.acquire()
328        try:
329            if not self._unfinished_tasks.acquire(False):
330                raise ValueError('task_done() called too many times')
331            if self._unfinished_tasks._semlock._is_zero():
332                self._cond.notify_all()
333        finally:
334            self._cond.release()
335
336    def join(self):
337        self._cond.acquire()
338        try:
339            if not self._unfinished_tasks._semlock._is_zero():
340                self._cond.wait()
341        finally:
342            self._cond.release()
343
344#
345# Simplified Queue type -- really just a locked pipe
346#
347
348class SimpleQueue(object):
349
350    def __init__(self):
351        self._reader, self._writer = Pipe(duplex=False)
352        self._rlock = Lock()
353        if sys.platform == 'win32':
354            self._wlock = None
355        else:
356            self._wlock = Lock()
357        self._make_methods()
358
359    def empty(self):
360        return not self._reader.poll()
361
362    def __getstate__(self):
363        assert_spawning(self)
364        return (self._reader, self._writer, self._rlock, self._wlock)
365
366    def __setstate__(self, state):
367        (self._reader, self._writer, self._rlock, self._wlock) = state
368        self._make_methods()
369
370    def _make_methods(self):
371        recv = self._reader.recv
372        racquire, rrelease = self._rlock.acquire, self._rlock.release
373        def get():
374            racquire()
375            try:
376                return recv()
377            finally:
378                rrelease()
379        self.get = get
380
381        if self._wlock is None:
382            # writes to a message oriented win32 pipe are atomic
383            self.put = self._writer.send
384        else:
385            send = self._writer.send
386            wacquire, wrelease = self._wlock.acquire, self._wlock.release
387            def put(obj):
388                wacquire()
389                try:
390                    return send(obj)
391                finally:
392                    wrelease()
393            self.put = put
394