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# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import atexit
import queue
import threading
import weakref
class Threading:
@staticmethod
def event_object(*args, **kwargs):
return threading.Event(*args, **kwargs)
@staticmethod
def lock_object(*args, **kwargs):
return threading.Lock(*args, **kwargs)
@staticmethod
def rlock_object(*args, **kwargs):
return threading.RLock(*args, **kwargs)
@staticmethod
def condition_object(*args, **kwargs):
return threading.Condition(*args, **kwargs)
_to_be_cleaned = weakref.WeakKeyDictionary()
_dying = False
class _Stopping(Exception):
pass
class ThreadWorker(threading.Thread):
MAX_IDLE_FOR = 1
def __init__(self, executor, work_queue):
super().__init__()
self.work_queue = work_queue
self.should_stop = False
self.idle = False
self.daemon = True
# Ensure that when the owning executor gets cleaned up that these
# threads also get shutdown (if they were not already shutdown).
self.executor_ref = weakref.ref(executor, lambda _obj: self.stop())
@classmethod
def create_and_register(cls, executor, work_queue):
w = cls(executor, work_queue)
# Ensure that on shutdown, if threads still exist that we get
# around to cleaning them up and waiting for them to correctly stop.
#
# TODO(harlowja): use a weakrefset in the future, as we don't
# really care about the values...
_to_be_cleaned[w] = True
return w
def _is_dying(self):
if self.should_stop or _dying:
return True
executor = self.executor_ref()
if executor is None:
return True
# Avoid confusing the GC with cycles (since each executor
# references its known workers)...
del executor
return False
def _wait_for_work(self):
self.idle = True
work = None
while work is None:
try:
work = self.work_queue.get(True, self.MAX_IDLE_FOR)
except queue.Empty:
if self._is_dying():
raise _Stopping()
self.idle = False
return work
def stop(self):
self.should_stop = True
def run(self):
while not self._is_dying():
try:
work = self._wait_for_work()
except _Stopping:
return
try:
work.run()
finally:
# Mark task as done for queue.join() support
self.work_queue.task_done()
# Avoid any potential (self) references to the work item
# in tracebacks or similar...
del work
def _clean_up():
"""Ensure all threads that were created were destroyed cleanly."""
global _dying
_dying = True
threads_to_wait_for = []
while _to_be_cleaned:
worker, _work_val = _to_be_cleaned.popitem()
worker.stop()
threads_to_wait_for.append(worker)
while threads_to_wait_for:
worker = threads_to_wait_for.pop()
try:
worker.join()
finally:
del worker
atexit.register(_clean_up)
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