121 lines
3.9 KiB
Python
121 lines
3.9 KiB
Python
# Copyright 2009 Brian Quinlan. All Rights Reserved.
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# Licensed to PSF under a Contributor Agreement.
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#
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# Copyright (C) 2013 Google Inc.
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# Changes to this file are licensed under the same terms as the original file
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# (the Python Software Foundation License).
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from __future__ import with_statement
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import threading
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import weakref
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import sys
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from concurrent.futures import _base
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try:
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import queue
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except ImportError:
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import Queue as queue
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# This file provides an UnsafeThreadPoolExecutor, which operates exactly like
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# the upstream Python version of ThreadPoolExecutor with one exception: it
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# doesn't wait for worker threads to finish before shutting down the Python
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# interpreter.
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#
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# This is dangerous for many workloads, but fine for some (like when threads
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# only send network requests). The YCM workload is one of those workloads where
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# it's safe (the aforementioned network requests case).
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class _WorkItem(object):
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def __init__(self, future, fn, args, kwargs):
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self.future = future
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self.fn = fn
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self.args = args
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self.kwargs = kwargs
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def run(self):
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if not self.future.set_running_or_notify_cancel():
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return
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try:
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result = self.fn(*self.args, **self.kwargs)
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except BaseException:
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e = sys.exc_info()[1]
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self.future.set_exception(e)
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else:
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self.future.set_result(result)
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def _worker(executor_reference, work_queue):
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try:
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while True:
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work_item = work_queue.get(block=True)
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if work_item is not None:
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work_item.run()
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continue
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executor = executor_reference()
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# Exit if:
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# - The executor that owns the worker has been collected OR
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# - The executor that owns the worker has been shutdown.
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if executor is None or executor._shutdown:
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# Notice other workers
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work_queue.put(None)
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return
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del executor
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except BaseException:
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_base.LOGGER.critical('Exception in worker', exc_info=True)
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class UnsafeThreadPoolExecutor(_base.Executor):
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def __init__(self, max_workers):
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"""Initializes a new ThreadPoolExecutor instance.
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Args:
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max_workers: The maximum number of threads that can be used to
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execute the given calls.
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"""
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self._max_workers = max_workers
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self._work_queue = queue.Queue()
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self._threads = set()
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self._shutdown = False
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self._shutdown_lock = threading.Lock()
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def submit(self, fn, *args, **kwargs):
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with self._shutdown_lock:
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if self._shutdown:
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raise RuntimeError('cannot schedule new futures after shutdown')
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f = _base.Future()
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w = _WorkItem(f, fn, args, kwargs)
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self._work_queue.put(w)
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self._adjust_thread_count()
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return f
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submit.__doc__ = _base.Executor.submit.__doc__
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def _adjust_thread_count(self):
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# When the executor gets lost, the weakref callback will wake up
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# the worker threads.
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def weakref_cb(_, q=self._work_queue):
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q.put(None)
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# TODO(bquinlan): Should avoid creating new threads if there are more
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# idle threads than items in the work queue.
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if len(self._threads) < self._max_workers:
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t = threading.Thread(target=_worker,
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args=(weakref.ref(self, weakref_cb),
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self._work_queue))
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t.daemon = True
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t.start()
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self._threads.add(t)
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def shutdown(self, wait=True):
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with self._shutdown_lock:
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self._shutdown = True
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self._work_queue.put(None)
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if wait:
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for t in self._threads:
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t.join()
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shutdown.__doc__ = _base.Executor.shutdown.__doc__
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