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###############################################################################
# Queue and SimpleQueue implementation for loky
#
# authors: Thomas Moreau, Olivier Grisel
#
# based on multiprocessing/queues.py (16/02/2017)
# * Add some custom reducers for the Queues/SimpleQueue to tweak the
# pickling process. (overload Queue._feed/SimpleQueue.put)
#
import os
import sys
import errno
import weakref
import threading
from multiprocessing import util
from multiprocessing.queues import (
Full,
Queue as mp_Queue,
SimpleQueue as mp_SimpleQueue,
_sentinel,
)
from multiprocessing.context import assert_spawning
from .reduction import dumps
__all__ = ["Queue", "SimpleQueue", "Full"]
class Queue(mp_Queue):
def __init__(self, maxsize=0, reducers=None, ctx=None):
super().__init__(maxsize=maxsize, ctx=ctx)
self._reducers = reducers
# Use custom queue set/get state to be able to reduce the custom reducers
def __getstate__(self):
assert_spawning(self)
return (
self._ignore_epipe,
self._maxsize,
self._reader,
self._writer,
self._reducers,
self._rlock,
self._wlock,
self._sem,
self._opid,
)
def __setstate__(self, state):
(
self._ignore_epipe,
self._maxsize,
self._reader,
self._writer,
self._reducers,
self._rlock,
self._wlock,
self._sem,
self._opid,
) = state
if sys.version_info >= (3, 9):
self._reset()
else:
self._after_fork()
# Overload _start_thread to correctly call our custom _feed
def _start_thread(self):
util.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._reducers,
self._ignore_epipe,
self._on_queue_feeder_error,
self._sem,
),
name="QueueFeederThread",
)
self._thread.daemon = True
util.debug("doing self._thread.start()")
self._thread.start()
util.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 = util.Finalize(
self._thread,
Queue._finalize_join,
[weakref.ref(self._thread)],
exitpriority=-5,
)
# Send sentinel to the thread queue object when garbage collected
self._close = util.Finalize(
self,
Queue._finalize_close,
[self._buffer, self._notempty],
exitpriority=10,
)
# Overload the _feed methods to use our custom pickling strategy.
@staticmethod
def _feed(
buffer,
notempty,
send_bytes,
writelock,
close,
reducers,
ignore_epipe,
onerror,
queue_sem,
):
util.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 True:
try:
nacquire()
try:
if not buffer:
nwait()
finally:
nrelease()
try:
while True:
obj = bpopleft()
if obj is sentinel:
util.debug("feeder thread got sentinel -- exiting")
close()
return
# serialize the data before acquiring the lock
obj_ = dumps(obj, reducers=reducers)
if wacquire is None:
send_bytes(obj_)
else:
wacquire()
try:
send_bytes(obj_)
finally:
wrelease()
# Remove references early to avoid leaking memory
del obj, obj_
except IndexError:
pass
except BaseException 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 util.is_exiting():
util.info(f"error in queue thread: {e}")
return
else:
queue_sem.release()
onerror(e, obj)
def _on_queue_feeder_error(self, 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()
class SimpleQueue(mp_SimpleQueue):
def __init__(self, reducers=None, ctx=None):
super().__init__(ctx=ctx)
# Add possiblity to use custom reducers
self._reducers = reducers
def close(self):
self._reader.close()
self._writer.close()
# Use custom queue set/get state to be able to reduce the custom reducers
def __getstate__(self):
assert_spawning(self)
return (
self._reader,
self._writer,
self._reducers,
self._rlock,
self._wlock,
)
def __setstate__(self, state):
(
self._reader,
self._writer,
self._reducers,
self._rlock,
self._wlock,
) = state
# Overload put to use our customizable reducer
def put(self, obj):
# serialize the data before acquiring the lock
obj = dumps(obj, reducers=self._reducers)
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)
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