| # |
| # Module implementing queues |
| # |
| # multiprocessing/queues.py |
| # |
| # Copyright (c) 2006-2008, R Oudkerk |
| # Licensed to PSF under a Contributor Agreement. |
| # |
| |
| __all__ = ['Queue', 'SimpleQueue', 'JoinableQueue'] |
| |
| import sys |
| import os |
| import threading |
| import collections |
| import time |
| import types |
| import weakref |
| import errno |
| |
| from queue import Empty, Full |
| |
| import _multiprocessing |
| |
| from . import connection |
| from . import context |
| _ForkingPickler = context.reduction.ForkingPickler |
| |
| from .util import debug, info, Finalize, register_after_fork, is_exiting |
| |
| # |
| # Queue type using a pipe, buffer and thread |
| # |
| |
| class Queue(object): |
| |
| def __init__(self, maxsize=0, *, ctx): |
| if maxsize <= 0: |
| # Can raise ImportError (see issues #3770 and #23400) |
| from .synchronize import SEM_VALUE_MAX as maxsize |
| self._maxsize = maxsize |
| self._reader, self._writer = connection.Pipe(duplex=False) |
| self._rlock = ctx.Lock() |
| self._opid = os.getpid() |
| if sys.platform == 'win32': |
| self._wlock = None |
| else: |
| self._wlock = ctx.Lock() |
| self._sem = ctx.BoundedSemaphore(maxsize) |
| # For use by concurrent.futures |
| self._ignore_epipe = False |
| self._reset() |
| |
| if sys.platform != 'win32': |
| register_after_fork(self, Queue._after_fork) |
| |
| def __getstate__(self): |
| context.assert_spawning(self) |
| return (self._ignore_epipe, self._maxsize, self._reader, self._writer, |
| self._rlock, self._wlock, self._sem, self._opid) |
| |
| def __setstate__(self, state): |
| (self._ignore_epipe, self._maxsize, self._reader, self._writer, |
| self._rlock, self._wlock, self._sem, self._opid) = state |
| self._reset() |
| |
| def _after_fork(self): |
| debug('Queue._after_fork()') |
| self._reset(after_fork=True) |
| |
| def _reset(self, after_fork=False): |
| if after_fork: |
| self._notempty._at_fork_reinit() |
| else: |
| 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_bytes = self._writer.send_bytes |
| self._recv_bytes = self._reader.recv_bytes |
| self._poll = self._reader.poll |
| |
| def put(self, obj, block=True, timeout=None): |
| if self._closed: |
| raise ValueError(f"Queue {self!r} is closed") |
| if not self._sem.acquire(block, timeout): |
| raise Full |
| |
| with self._notempty: |
| if self._thread is None: |
| self._start_thread() |
| self._buffer.append(obj) |
| self._notempty.notify() |
| |
| def get(self, block=True, timeout=None): |
| if self._closed: |
| raise ValueError(f"Queue {self!r} is closed") |
| if block and timeout is None: |
| with self._rlock: |
| res = self._recv_bytes() |
| self._sem.release() |
| else: |
| if block: |
| deadline = time.monotonic() + timeout |
| if not self._rlock.acquire(block, timeout): |
| raise Empty |
| try: |
| if block: |
| timeout = deadline - time.monotonic() |
| if not self._poll(timeout): |
| raise Empty |
| elif not self._poll(): |
| raise Empty |
| res = self._recv_bytes() |
| self._sem.release() |
| finally: |
| self._rlock.release() |
| # unserialize the data after having released the lock |
| return _ForkingPickler.loads(res) |
| |
| 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 |
| try: |
| self._reader.close() |
| finally: |
| close = self._close |
| if close: |
| self._close = None |
| close() |
| |
| def join_thread(self): |
| debug('Queue.join_thread()') |
| assert self._closed, "Queue {0!r} not closed".format(self) |
| 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_bytes, |
| self._wlock, self._writer.close, self._ignore_epipe, |
| self._on_queue_feeder_error, self._sem), |
| name='QueueFeederThread' |
| ) |
| self._thread.daemon = True |
| |
| debug('doing self._thread.start()') |
| self._thread.start() |
| debug('... done self._thread.start()') |
| |
| if not self._joincancelled: |
| 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') |
| with notempty: |
| buffer.append(_sentinel) |
| notempty.notify() |
| |
| @staticmethod |
| def _feed(buffer, notempty, send_bytes, writelock, close, ignore_epipe, |
| onerror, queue_sem): |
| debug('starting thread to feed data to pipe') |
| 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 |
| |
| while 1: |
| try: |
| 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 |
| |
| # serialize the data before acquiring the lock |
| obj = _ForkingPickler.dumps(obj) |
| if wacquire is None: |
| send_bytes(obj) |
| else: |
| wacquire() |
| try: |
| send_bytes(obj) |
| finally: |
| wrelease() |
| except IndexError: |
| pass |
| except Exception as e: |
| if ignore_epipe and getattr(e, 'errno', 0) == errno.EPIPE: |
| return |
| # 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. |
| if is_exiting(): |
| info('error in queue thread: %s', e) |
| return |
| else: |
| # Since the object has not been sent in the queue, we need |
| # to decrease the size of the queue. The error acts as |
| # if the object had been silently removed from the queue |
| # and this step is necessary to have a properly working |
| # queue. |
| queue_sem.release() |
| onerror(e, obj) |
| |
| @staticmethod |
| def _on_queue_feeder_error(e, obj): |
| """ |
| Private API hook called when feeding data in the background thread |
| raises an exception. For overriding by concurrent.futures. |
| """ |
| import traceback |
| traceback.print_exc() |
| |
| |
| _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, *, ctx): |
| Queue.__init__(self, maxsize, ctx=ctx) |
| self._unfinished_tasks = ctx.Semaphore(0) |
| self._cond = ctx.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): |
| if self._closed: |
| raise ValueError(f"Queue {self!r} is closed") |
| if not self._sem.acquire(block, timeout): |
| raise Full |
| |
| with self._notempty, self._cond: |
| if self._thread is None: |
| self._start_thread() |
| self._buffer.append(obj) |
| self._unfinished_tasks.release() |
| self._notempty.notify() |
| |
| def task_done(self): |
| with self._cond: |
| 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() |
| |
| def join(self): |
| with self._cond: |
| if not self._unfinished_tasks._semlock._is_zero(): |
| self._cond.wait() |
| |
| # |
| # Simplified Queue type -- really just a locked pipe |
| # |
| |
| class SimpleQueue(object): |
| |
| def __init__(self, *, ctx): |
| self._reader, self._writer = connection.Pipe(duplex=False) |
| self._rlock = ctx.Lock() |
| self._poll = self._reader.poll |
| if sys.platform == 'win32': |
| self._wlock = None |
| else: |
| self._wlock = ctx.Lock() |
| |
| def close(self): |
| self._reader.close() |
| self._writer.close() |
| |
| def empty(self): |
| return not self._poll() |
| |
| def __getstate__(self): |
| context.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._poll = self._reader.poll |
| |
| def get(self): |
| with self._rlock: |
| res = self._reader.recv_bytes() |
| # unserialize the data after having released the lock |
| return _ForkingPickler.loads(res) |
| |
| def put(self, obj): |
| # serialize the data before acquiring the lock |
| obj = _ForkingPickler.dumps(obj) |
| if self._wlock is None: |
| # writes to a message oriented win32 pipe are atomic |
| self._writer.send_bytes(obj) |
| else: |
| with self._wlock: |
| self._writer.send_bytes(obj) |
| |
| __class_getitem__ = classmethod(types.GenericAlias) |
