bpo-39349: Add *cancel_futures* to Executor.shutdown() (GH-18057)

1 files changed, 14 insertions, 1 deletions

diff --git a/Lib/concurrent/futures/thread.py b/Lib/concurrent/futures/thread.py
index b89f8f24d4..be79161bf8 100644
--- a/Lib/concurrent/futures/thread.py
+++ b/Lib/concurrent/futures/thread.py
@@ -215,9 +215,22 @@ class ThreadPoolExecutor(_base.Executor):
                 if work_item is not None:
                     work_item.future.set_exception(BrokenThreadPool(self._broken))
 
-    def shutdown(self, wait=True):
+    def shutdown(self, wait=True, *, cancel_futures=False):
         with self._shutdown_lock:
             self._shutdown = True
+            if cancel_futures:
+                # Drain all work items from the queue, and then cancel their
+                # associated futures.
+                while True:
+                    try:
+                        work_item = self._work_queue.get_nowait()
+                    except queue.Empty:
+                        break
+                    if work_item is not None:
+                        work_item.future.cancel()
+
+            # Send a wake-up to prevent threads calling
+            # _work_queue.get(block=True) from permanently blocking.
             self._work_queue.put(None)
         if wait:
             for t in self._threads: