bpo-21423: Add an initializer argument to {Process,Thread}PoolExecutor (#4241)
* bpo-21423: Add an initializer argument to {Process,Thread}PoolExecutor
* Fix docstring
diff --git a/Lib/concurrent/futures/thread.py b/Lib/concurrent/futures/thread.py
index 0b5d537..2e7100b 100644
--- a/Lib/concurrent/futures/thread.py
+++ b/Lib/concurrent/futures/thread.py
@@ -41,6 +41,7 @@
atexit.register(_python_exit)
+
class _WorkItem(object):
def __init__(self, future, fn, args, kwargs):
self.future = future
@@ -61,7 +62,17 @@
else:
self.future.set_result(result)
-def _worker(executor_reference, work_queue):
+
+def _worker(executor_reference, work_queue, initializer, initargs):
+ if initializer is not None:
+ try:
+ initializer(*initargs)
+ except BaseException:
+ _base.LOGGER.critical('Exception in initializer:', exc_info=True)
+ executor = executor_reference()
+ if executor is not None:
+ executor._initializer_failed()
+ return
try:
while True:
work_item = work_queue.get(block=True)
@@ -83,18 +94,28 @@
except BaseException:
_base.LOGGER.critical('Exception in worker', exc_info=True)
+
+class BrokenThreadPool(_base.BrokenExecutor):
+ """
+ Raised when a worker thread in a ThreadPoolExecutor failed initializing.
+ """
+
+
class ThreadPoolExecutor(_base.Executor):
# Used to assign unique thread names when thread_name_prefix is not supplied.
_counter = itertools.count().__next__
- def __init__(self, max_workers=None, thread_name_prefix=''):
+ def __init__(self, max_workers=None, thread_name_prefix='',
+ initializer=None, initargs=()):
"""Initializes a new ThreadPoolExecutor instance.
Args:
max_workers: The maximum number of threads that can be used to
execute the given calls.
thread_name_prefix: An optional name prefix to give our threads.
+ initializer: An callable used to initialize worker threads.
+ initargs: A tuple of arguments to pass to the initializer.
"""
if max_workers is None:
# Use this number because ThreadPoolExecutor is often
@@ -103,16 +124,25 @@
if max_workers <= 0:
raise ValueError("max_workers must be greater than 0")
+ if initializer is not None and not callable(initializer):
+ raise TypeError("initializer must be a callable")
+
self._max_workers = max_workers
self._work_queue = queue.Queue()
self._threads = set()
+ self._broken = False
self._shutdown = False
self._shutdown_lock = threading.Lock()
self._thread_name_prefix = (thread_name_prefix or
("ThreadPoolExecutor-%d" % self._counter()))
+ self._initializer = initializer
+ self._initargs = initargs
def submit(self, fn, *args, **kwargs):
with self._shutdown_lock:
+ if self._broken:
+ raise BrokenThreadPool(self._broken)
+
if self._shutdown:
raise RuntimeError('cannot schedule new futures after shutdown')
@@ -137,12 +167,27 @@
num_threads)
t = threading.Thread(name=thread_name, target=_worker,
args=(weakref.ref(self, weakref_cb),
- self._work_queue))
+ self._work_queue,
+ self._initializer,
+ self._initargs))
t.daemon = True
t.start()
self._threads.add(t)
_threads_queues[t] = self._work_queue
+ def _initializer_failed(self):
+ with self._shutdown_lock:
+ self._broken = ('A thread initializer failed, the thread pool '
+ 'is not usable anymore')
+ # Drain work queue and mark pending futures failed
+ while True:
+ try:
+ work_item = self._work_queue.get_nowait()
+ except queue.Empty:
+ break
+ if work_item is not None:
+ work_item.future.set_exception(BrokenThreadPool(self._broken))
+
def shutdown(self, wait=True):
with self._shutdown_lock:
self._shutdown = True