Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 1 | # |
| 2 | # Module implementing queues |
| 3 | # |
| 4 | # multiprocessing/queues.py |
| 5 | # |
R. David Murray | 3fc969a | 2010-12-14 01:38:16 +0000 | [diff] [blame] | 6 | # Copyright (c) 2006-2008, R Oudkerk |
Richard Oudkerk | 3e268aa | 2012-04-30 12:13:55 +0100 | [diff] [blame^] | 7 | # Licensed to PSF under a Contributor Agreement. |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 8 | # |
| 9 | |
Jesse Noller | 14f3ae2 | 2009-03-31 03:37:07 +0000 | [diff] [blame] | 10 | __all__ = ['Queue', 'SimpleQueue', 'JoinableQueue'] |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 11 | |
| 12 | import sys |
| 13 | import os |
| 14 | import threading |
| 15 | import collections |
| 16 | import time |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 17 | import weakref |
Antoine Pitrou | dc19c24 | 2011-07-16 01:51:58 +0200 | [diff] [blame] | 18 | import errno |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 19 | |
| 20 | from queue import Empty, Full |
| 21 | import _multiprocessing |
Antoine Pitrou | bdb1cf1 | 2012-03-05 19:28:37 +0100 | [diff] [blame] | 22 | from multiprocessing.connection import Pipe |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 23 | from multiprocessing.synchronize import Lock, BoundedSemaphore, Semaphore, Condition |
| 24 | from multiprocessing.util import debug, info, Finalize, register_after_fork |
| 25 | from multiprocessing.forking import assert_spawning |
| 26 | |
| 27 | # |
| 28 | # Queue type using a pipe, buffer and thread |
| 29 | # |
| 30 | |
| 31 | class Queue(object): |
| 32 | |
| 33 | def __init__(self, maxsize=0): |
| 34 | if maxsize <= 0: |
| 35 | maxsize = _multiprocessing.SemLock.SEM_VALUE_MAX |
| 36 | self._maxsize = maxsize |
| 37 | self._reader, self._writer = Pipe(duplex=False) |
| 38 | self._rlock = Lock() |
| 39 | self._opid = os.getpid() |
| 40 | if sys.platform == 'win32': |
| 41 | self._wlock = None |
| 42 | else: |
| 43 | self._wlock = Lock() |
| 44 | self._sem = BoundedSemaphore(maxsize) |
Antoine Pitrou | dc19c24 | 2011-07-16 01:51:58 +0200 | [diff] [blame] | 45 | # For use by concurrent.futures |
| 46 | self._ignore_epipe = False |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 47 | |
| 48 | self._after_fork() |
| 49 | |
| 50 | if sys.platform != 'win32': |
| 51 | register_after_fork(self, Queue._after_fork) |
| 52 | |
| 53 | def __getstate__(self): |
| 54 | assert_spawning(self) |
Antoine Pitrou | fb96089 | 2011-07-20 02:01:39 +0200 | [diff] [blame] | 55 | return (self._ignore_epipe, self._maxsize, self._reader, self._writer, |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 56 | self._rlock, self._wlock, self._sem, self._opid) |
| 57 | |
| 58 | def __setstate__(self, state): |
Antoine Pitrou | fb96089 | 2011-07-20 02:01:39 +0200 | [diff] [blame] | 59 | (self._ignore_epipe, self._maxsize, self._reader, self._writer, |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 60 | self._rlock, self._wlock, self._sem, self._opid) = state |
| 61 | self._after_fork() |
| 62 | |
| 63 | def _after_fork(self): |
| 64 | debug('Queue._after_fork()') |
| 65 | self._notempty = threading.Condition(threading.Lock()) |
| 66 | self._buffer = collections.deque() |
| 67 | self._thread = None |
| 68 | self._jointhread = None |
| 69 | self._joincancelled = False |
| 70 | self._closed = False |
| 71 | self._close = None |
| 72 | self._send = self._writer.send |
| 73 | self._recv = self._reader.recv |
| 74 | self._poll = self._reader.poll |
| 75 | |
| 76 | def put(self, obj, block=True, timeout=None): |
| 77 | assert not self._closed |
| 78 | if not self._sem.acquire(block, timeout): |
| 79 | raise Full |
| 80 | |
| 81 | self._notempty.acquire() |
| 82 | try: |
| 83 | if self._thread is None: |
| 84 | self._start_thread() |
| 85 | self._buffer.append(obj) |
| 86 | self._notempty.notify() |
| 87 | finally: |
| 88 | self._notempty.release() |
| 89 | |
| 90 | def get(self, block=True, timeout=None): |
| 91 | if block and timeout is None: |
| 92 | self._rlock.acquire() |
| 93 | try: |
| 94 | res = self._recv() |
| 95 | self._sem.release() |
| 96 | return res |
| 97 | finally: |
| 98 | self._rlock.release() |
| 99 | |
| 100 | else: |
| 101 | if block: |
| 102 | deadline = time.time() + timeout |
| 103 | if not self._rlock.acquire(block, timeout): |
| 104 | raise Empty |
| 105 | try: |
Antoine Pitrou | a365113 | 2011-11-10 00:37:09 +0100 | [diff] [blame] | 106 | if block: |
| 107 | timeout = deadline - time.time() |
| 108 | if timeout < 0 or not self._poll(timeout): |
| 109 | raise Empty |
| 110 | elif not self._poll(): |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 111 | raise Empty |
| 112 | res = self._recv() |
| 113 | self._sem.release() |
| 114 | return res |
| 115 | finally: |
| 116 | self._rlock.release() |
| 117 | |
| 118 | def qsize(self): |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 119 | # Raises NotImplementedError on Mac OSX because of broken sem_getvalue() |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 120 | return self._maxsize - self._sem._semlock._get_value() |
| 121 | |
| 122 | def empty(self): |
| 123 | return not self._poll() |
| 124 | |
| 125 | def full(self): |
| 126 | return self._sem._semlock._is_zero() |
| 127 | |
| 128 | def get_nowait(self): |
| 129 | return self.get(False) |
| 130 | |
| 131 | def put_nowait(self, obj): |
| 132 | return self.put(obj, False) |
| 133 | |
| 134 | def close(self): |
| 135 | self._closed = True |
| 136 | self._reader.close() |
| 137 | if self._close: |
| 138 | self._close() |
| 139 | |
| 140 | def join_thread(self): |
| 141 | debug('Queue.join_thread()') |
| 142 | assert self._closed |
| 143 | if self._jointhread: |
| 144 | self._jointhread() |
| 145 | |
| 146 | def cancel_join_thread(self): |
| 147 | debug('Queue.cancel_join_thread()') |
| 148 | self._joincancelled = True |
| 149 | try: |
| 150 | self._jointhread.cancel() |
| 151 | except AttributeError: |
| 152 | pass |
| 153 | |
| 154 | def _start_thread(self): |
| 155 | debug('Queue._start_thread()') |
| 156 | |
| 157 | # Start thread which transfers data from buffer to pipe |
| 158 | self._buffer.clear() |
| 159 | self._thread = threading.Thread( |
| 160 | target=Queue._feed, |
| 161 | args=(self._buffer, self._notempty, self._send, |
Antoine Pitrou | dc19c24 | 2011-07-16 01:51:58 +0200 | [diff] [blame] | 162 | self._wlock, self._writer.close, self._ignore_epipe), |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 163 | name='QueueFeederThread' |
| 164 | ) |
Benjamin Peterson | 7275370 | 2008-08-18 18:09:21 +0000 | [diff] [blame] | 165 | self._thread.daemon = True |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 166 | |
| 167 | debug('doing self._thread.start()') |
| 168 | self._thread.start() |
| 169 | debug('... done self._thread.start()') |
| 170 | |
| 171 | # On process exit we will wait for data to be flushed to pipe. |
| 172 | # |
| 173 | # However, if this process created the queue then all |
| 174 | # processes which use the queue will be descendants of this |
| 175 | # process. Therefore waiting for the queue to be flushed |
| 176 | # is pointless once all the child processes have been joined. |
| 177 | created_by_this_process = (self._opid == os.getpid()) |
| 178 | if not self._joincancelled and not created_by_this_process: |
| 179 | self._jointhread = Finalize( |
| 180 | self._thread, Queue._finalize_join, |
| 181 | [weakref.ref(self._thread)], |
| 182 | exitpriority=-5 |
| 183 | ) |
| 184 | |
| 185 | # Send sentinel to the thread queue object when garbage collected |
| 186 | self._close = Finalize( |
| 187 | self, Queue._finalize_close, |
| 188 | [self._buffer, self._notempty], |
| 189 | exitpriority=10 |
| 190 | ) |
| 191 | |
| 192 | @staticmethod |
| 193 | def _finalize_join(twr): |
| 194 | debug('joining queue thread') |
| 195 | thread = twr() |
| 196 | if thread is not None: |
| 197 | thread.join() |
| 198 | debug('... queue thread joined') |
| 199 | else: |
| 200 | debug('... queue thread already dead') |
| 201 | |
| 202 | @staticmethod |
| 203 | def _finalize_close(buffer, notempty): |
| 204 | debug('telling queue thread to quit') |
| 205 | notempty.acquire() |
| 206 | try: |
| 207 | buffer.append(_sentinel) |
| 208 | notempty.notify() |
| 209 | finally: |
| 210 | notempty.release() |
| 211 | |
| 212 | @staticmethod |
Antoine Pitrou | dc19c24 | 2011-07-16 01:51:58 +0200 | [diff] [blame] | 213 | def _feed(buffer, notempty, send, writelock, close, ignore_epipe): |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 214 | debug('starting thread to feed data to pipe') |
| 215 | from .util import is_exiting |
| 216 | |
| 217 | nacquire = notempty.acquire |
| 218 | nrelease = notempty.release |
| 219 | nwait = notempty.wait |
| 220 | bpopleft = buffer.popleft |
| 221 | sentinel = _sentinel |
| 222 | if sys.platform != 'win32': |
| 223 | wacquire = writelock.acquire |
| 224 | wrelease = writelock.release |
| 225 | else: |
| 226 | wacquire = None |
| 227 | |
| 228 | try: |
| 229 | while 1: |
| 230 | nacquire() |
| 231 | try: |
| 232 | if not buffer: |
| 233 | nwait() |
| 234 | finally: |
| 235 | nrelease() |
| 236 | try: |
| 237 | while 1: |
| 238 | obj = bpopleft() |
| 239 | if obj is sentinel: |
| 240 | debug('feeder thread got sentinel -- exiting') |
| 241 | close() |
| 242 | return |
| 243 | |
| 244 | if wacquire is None: |
| 245 | send(obj) |
| 246 | else: |
| 247 | wacquire() |
| 248 | try: |
| 249 | send(obj) |
| 250 | finally: |
| 251 | wrelease() |
| 252 | except IndexError: |
| 253 | pass |
| 254 | except Exception as e: |
Antoine Pitrou | dc19c24 | 2011-07-16 01:51:58 +0200 | [diff] [blame] | 255 | if ignore_epipe and getattr(e, 'errno', 0) == errno.EPIPE: |
| 256 | return |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 257 | # Since this runs in a daemon thread the resources it uses |
| 258 | # may be become unusable while the process is cleaning up. |
| 259 | # We ignore errors which happen after the process has |
| 260 | # started to cleanup. |
| 261 | try: |
| 262 | if is_exiting(): |
| 263 | info('error in queue thread: %s', e) |
| 264 | else: |
| 265 | import traceback |
| 266 | traceback.print_exc() |
| 267 | except Exception: |
| 268 | pass |
| 269 | |
| 270 | _sentinel = object() |
| 271 | |
| 272 | # |
| 273 | # A queue type which also supports join() and task_done() methods |
| 274 | # |
| 275 | # Note that if you do not call task_done() for each finished task then |
| 276 | # eventually the counter's semaphore may overflow causing Bad Things |
| 277 | # to happen. |
| 278 | # |
| 279 | |
| 280 | class JoinableQueue(Queue): |
| 281 | |
| 282 | def __init__(self, maxsize=0): |
| 283 | Queue.__init__(self, maxsize) |
| 284 | self._unfinished_tasks = Semaphore(0) |
| 285 | self._cond = Condition() |
| 286 | |
| 287 | def __getstate__(self): |
| 288 | return Queue.__getstate__(self) + (self._cond, self._unfinished_tasks) |
| 289 | |
| 290 | def __setstate__(self, state): |
| 291 | Queue.__setstate__(self, state[:-2]) |
| 292 | self._cond, self._unfinished_tasks = state[-2:] |
| 293 | |
Benjamin Peterson | 8719ad5 | 2009-09-11 22:24:02 +0000 | [diff] [blame] | 294 | def put(self, obj, block=True, timeout=None): |
| 295 | assert not self._closed |
| 296 | if not self._sem.acquire(block, timeout): |
| 297 | raise Full |
| 298 | |
| 299 | self._notempty.acquire() |
| 300 | self._cond.acquire() |
| 301 | try: |
| 302 | if self._thread is None: |
| 303 | self._start_thread() |
| 304 | self._buffer.append(obj) |
| 305 | self._unfinished_tasks.release() |
| 306 | self._notempty.notify() |
| 307 | finally: |
| 308 | self._cond.release() |
| 309 | self._notempty.release() |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 310 | |
| 311 | def task_done(self): |
| 312 | self._cond.acquire() |
| 313 | try: |
| 314 | if not self._unfinished_tasks.acquire(False): |
| 315 | raise ValueError('task_done() called too many times') |
| 316 | if self._unfinished_tasks._semlock._is_zero(): |
| 317 | self._cond.notify_all() |
| 318 | finally: |
| 319 | self._cond.release() |
| 320 | |
| 321 | def join(self): |
| 322 | self._cond.acquire() |
| 323 | try: |
| 324 | if not self._unfinished_tasks._semlock._is_zero(): |
| 325 | self._cond.wait() |
| 326 | finally: |
| 327 | self._cond.release() |
| 328 | |
| 329 | # |
| 330 | # Simplified Queue type -- really just a locked pipe |
| 331 | # |
| 332 | |
| 333 | class SimpleQueue(object): |
| 334 | |
| 335 | def __init__(self): |
| 336 | self._reader, self._writer = Pipe(duplex=False) |
| 337 | self._rlock = Lock() |
Antoine Pitrou | bdb1cf1 | 2012-03-05 19:28:37 +0100 | [diff] [blame] | 338 | self._poll = self._reader.poll |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 339 | if sys.platform == 'win32': |
| 340 | self._wlock = None |
| 341 | else: |
| 342 | self._wlock = Lock() |
| 343 | self._make_methods() |
| 344 | |
| 345 | def empty(self): |
Antoine Pitrou | bdb1cf1 | 2012-03-05 19:28:37 +0100 | [diff] [blame] | 346 | return not self._poll() |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 347 | |
| 348 | def __getstate__(self): |
| 349 | assert_spawning(self) |
| 350 | return (self._reader, self._writer, self._rlock, self._wlock) |
| 351 | |
| 352 | def __setstate__(self, state): |
| 353 | (self._reader, self._writer, self._rlock, self._wlock) = state |
| 354 | self._make_methods() |
| 355 | |
| 356 | def _make_methods(self): |
| 357 | recv = self._reader.recv |
| 358 | racquire, rrelease = self._rlock.acquire, self._rlock.release |
Antoine Pitrou | bdb1cf1 | 2012-03-05 19:28:37 +0100 | [diff] [blame] | 359 | def get(): |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 360 | racquire() |
| 361 | try: |
Antoine Pitrou | bdb1cf1 | 2012-03-05 19:28:37 +0100 | [diff] [blame] | 362 | return recv() |
Benjamin Peterson | e711caf | 2008-06-11 16:44:04 +0000 | [diff] [blame] | 363 | finally: |
| 364 | rrelease() |
| 365 | self.get = get |
| 366 | |
| 367 | if self._wlock is None: |
| 368 | # writes to a message oriented win32 pipe are atomic |
| 369 | self.put = self._writer.send |
| 370 | else: |
| 371 | send = self._writer.send |
| 372 | wacquire, wrelease = self._wlock.acquire, self._wlock.release |
| 373 | def put(obj): |
| 374 | wacquire() |
| 375 | try: |
| 376 | return send(obj) |
| 377 | finally: |
| 378 | wrelease() |
| 379 | self.put = put |