python · aeros · Sep 24, 2019 · Sep 24, 2019 · Sep 24, 2019 · Sep 24, 2019
@@ -167,13 +167,20 @@ Running and stopping the loop
 
    .. versionadded:: 3.6
 
-.. coroutinemethod:: loop.shutdown_default_executor()
+.. coroutinemethod:: loop.shutdown_default_executor(timeout=None)
 
    Schedule the closure of the default executor and wait for it to join all of
    the threads in the :class:`ThreadPoolExecutor`. After calling this method, a
    :exc:`RuntimeError` will be raised if :meth:`loop.run_in_executor` is called
    while using the default executor.
 
+   The *timeout* parameter specifies the amount of time the threadpool will
+   be given to finish joining. The default value is ``None``, which means the
+   threadpool will be given an indefinite amount of time.
+
+   If the timeout duration is reached, a warning is emitted and threadpool is
+   terminated without waiting for its threads to finish joining.
+
    Note that there is no need to call this function when
    :func:`asyncio.run` is used.
 

@@ -227,6 +227,10 @@ Running an asyncio Program
     the end.  It should be used as a main entry point for asyncio
     programs, and should ideally only be called once.
 
+    The threadpool is given a timeout duration of 5 minutes to join its threads.
+    If the threadpool hasn't finishing joining within that duration, a warning is
+    emitted and the threadpool is closed.
+
     Example::
 
         async def main():

@@ -549,8 +549,13 @@ async def shutdown_asyncgens(self):
                     'asyncgen': agen
                 })
 
-    async def shutdown_default_executor(self):
-        """Schedule the shutdown of the default executor."""
+    async def shutdown_default_executor(self, timeout=None):
+        """Schedule the shutdown of the default executor.
+
+        The timeout parameter specifies the amount of time the threadpool will
+        be given to finish joining. The default value is None, which means
+        that the threadpool will be given an indefinite amount of time.
+        """
         self._executor_shutdown_called = True
         if self._default_executor is None:
             return
@@ -560,7 +565,13 @@ async def shutdown_default_executor(self):
         try:
             await future
         finally:
-            thread.join()
+            thread.join(timeout)
+
+        if thread.is_alive():
+            warnings.warn("The ThreadPoolExecutor did not finishing joining "
+                             f"its threads within {timeout} seconds.",
+                             RuntimeWarning, stacklevel=2)
+            self._default_executor.shutdown(wait=False)
 
     def _do_shutdown(self, future):
         try:

@@ -5,12 +5,16 @@
 from . import tasks
 
 
+# Default timeout for joining the threads in the threadpool
+THREAD_JOIN_TIMEOUT = 300
+
+
 def run(main, *, debug=False):
     """Execute the coroutine and return the result.
 
     This function runs the passed coroutine, taking care of
-    managing the asyncio event loop and finalizing asynchronous
-    generators.
+    managing the asyncio event loop, finalizing asynchronous
+    generators, and closing the threadpool.
 
     This function cannot be called when another asyncio event loop is
     running in the same thread.
@@ -21,6 +25,9 @@ def run(main, *, debug=False):
     It should be used as a main entry point for asyncio programs, and should
     ideally only be called once.
 
+    The threadpool is given a timeout duration of 5 minutes. If its threads
+    haven't finishing joining within that duration, the threadpool is terminated.
+
     Example:
 
         async def main():
@@ -45,7 +52,8 @@ async def main():
         try:
             _cancel_all_tasks(loop)
             loop.run_until_complete(loop.shutdown_asyncgens())
-            loop.run_until_complete(loop.shutdown_default_executor())
+            loop.run_until_complete(
+                loop.shutdown_default_executor(timeout=THREAD_JOIN_TIMEOUT))
         finally:
             events.set_event_loop(None)
             loop.close()

diff --git a/Misc/NEWS.d/next/Library/2019-09-25-00-37-51.bpo-38267.X9Jb5V.rst b/Misc/NEWS.d/next/Library/2019-09-25-00-37-51.bpo-38267.X9Jb5V.rst
@@ -0,0 +1 @@
+Add *timeout* parameter to :meth:`asyncio.loop.shutdown_default_executor`.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Add timeout parameter to :meth:`asyncio.loop.shutdown_default_executor`.