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Diffstat (limited to 'src/buildstream/_platform/multiprocessing.py')
| -rw-r--r-- | src/buildstream/_platform/multiprocessing.py | 108 |
1 files changed, 0 insertions, 108 deletions
diff --git a/src/buildstream/_platform/multiprocessing.py b/src/buildstream/_platform/multiprocessing.py deleted file mode 100644 index c036651e7..000000000 --- a/src/buildstream/_platform/multiprocessing.py +++ /dev/null @@ -1,108 +0,0 @@ -# -# Copyright (C) 2019 Bloomberg Finance LP -# -# This program is free software; you can redistribute it and/or -# modify it under the terms of the GNU Lesser General Public -# License as published by the Free Software Foundation; either -# version 2 of the License, or (at your option) any later version. -# -# This library is distributed in the hope that it will be useful, -# but WITHOUT ANY WARRANTY; without even the implied warranty of -# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU -# Lesser General Public License for more details. -# -# You should have received a copy of the GNU Lesser General Public -# License along with this library. If not, see <http://www.gnu.org/licenses/>. -# - -import multiprocessing - - -# QueueManager() -# -# This abstracts our choice of creating picklable or non-picklable Queues. -# -# Note that when choosing the 'spawn' or 'forkserver' methods of starting -# processes with the `multiprocessing` standard library module, we must use -# only picklable type as parameters to jobs. -# -class QueueManager: - def make_queue_wrapper(self): - return _PlainQueueWrapper(multiprocessing.Queue()) - - -# PicklableQueueManager() -# -# A QueueManager that creates pickable types. -# -# Note that the requirement of being picklable adds extra runtime burden, as we -# must create and maintain a `SyncManager` process that will create and manage -# the real objects. -# -class PicklableQueueManager(QueueManager): - def __init__(self): - super().__init__() - self._manager = None - - def make_queue_wrapper(self): - # Only SyncManager Queues are picklable, so we must make those. Avoid - # creating multiple expensive SyncManagers, by keeping this one around. - if self._manager is None: - self._manager = multiprocessing.Manager() - return _SyncManagerQueueWrapper(self._manager.Queue()) - - -# QueueWrapper() -# -# This abstracts our choice of using picklable or non-picklable Queues. -# -class QueueWrapper: - pass - - -class _PlainQueueWrapper(QueueWrapper): - def __init__(self, queue): - super().__init__() - self.queue = queue - - def set_potential_callback_on_queue_event(self, event_loop, callback): - # Warning: Platform specific code up ahead - # - # The multiprocessing.Queue object does not tell us how - # to receive io events in the receiving process, so we - # need to sneak in and get its file descriptor. - # - # The _reader member of the Queue is currently private - # but well known, perhaps it will become public: - # - # http://bugs.python.org/issue3831 - # - event_loop.add_reader(self.queue._reader.fileno(), callback) - - def clear_potential_callback_on_queue_event(self, event_loop): - event_loop.remove_reader(self.queue._reader.fileno()) - - def close(self): - self.queue.close() - - -class _SyncManagerQueueWrapper(QueueWrapper): - def __init__(self, queue): - super().__init__() - self.queue = queue - - def set_potential_callback_on_queue_event(self, event_loop, callback): - # We can't easily support these callbacks for Queues managed by a - # SyncManager, so don't support them for now. In later work we should - # be able to support them with threading. - pass - - def clear_potential_callback_on_queue_event(self, event_loop): - pass - - def close(self): - # SyncManager queue proxies do not have a `close()` method, they rely - # on a callback on garbage collection to release resources. For our - # purposes the queue is invalid after closing, so it's ok to release it - # here. - self.queue = None |