# HG changeset patch
# User Augie Fackler <augie@google.com>
# Date 1470061908 14400
#      Mon Aug 01 10:31:48 2016 -0400
# Node ID 62e0918e62454d03a337b9de7288f235dd1a5b17
# Parent  6c2e2de5ab8e8276b6daea3c601c89024bc9fa20
concurrent.futures.ThreadPoolExecutor: add support for naming threads

This is sometimes useful when binaries contain many thread pools, as
it's now possible to figure out what category of thread is stuck.

diff --git a/Lib/concurrent/futures/thread.py b/Lib/concurrent/futures/thread.py
--- a/Lib/concurrent/futures/thread.py
+++ b/Lib/concurrent/futures/thread.py
@@ -81,7 +81,7 @@ def _worker(executor_reference, work_que
         _base.LOGGER.critical('Exception in worker', exc_info=True)
 
 class ThreadPoolExecutor(_base.Executor):
-    def __init__(self, max_workers=None):
+    def __init__(self, max_workers=None, thread_name_prefix=None):
         """Initializes a new ThreadPoolExecutor instance.
 
         Args:
@@ -100,6 +100,7 @@ class ThreadPoolExecutor(_base.Executor)
         self._threads = set()
         self._shutdown = False
         self._shutdown_lock = threading.Lock()
+        self._thread_name_prefix = thread_name_prefix
 
     def submit(self, fn, *args, **kwargs):
         with self._shutdown_lock:
@@ -122,7 +123,11 @@ class ThreadPoolExecutor(_base.Executor)
         # TODO(bquinlan): Should avoid creating new threads if there are more
         # idle threads than items in the work queue.
         if len(self._threads) < self._max_workers:
-            t = threading.Thread(target=_worker,
+            if self._thread_name_prefix:
+                name = self._thread_name_prefix + '_%d' % len(self._threads)
+            else:
+                name = None
+            t = threading.Thread(name=name, target=_worker,
                                  args=(weakref.ref(self, weakref_cb),
                                        self._work_queue))
             t.daemon = True
diff --git a/Lib/test/test_concurrent_futures.py b/Lib/test/test_concurrent_futures.py
--- a/Lib/test/test_concurrent_futures.py
+++ b/Lib/test/test_concurrent_futures.py
@@ -154,6 +154,17 @@ class ThreadPoolShutdownTest(ThreadPoolM
         for t in threads:
             t.join()
 
+    def test_thread_names(self):
+        executor = futures.ThreadPoolExecutor(
+            max_workers=5, thread_name_prefix='SpecialPool')
+        executor.map(abs, range(-5, 5))
+        threads = executor._threads
+        del executor
+
+        for t in threads:
+            self.assertRegex(t.name, '^SpecialPool_[0-4]$')
+            t.join()
+
 
 class ProcessPoolShutdownTest(ProcessPoolMixin, ExecutorShutdownTest, unittest.TestCase):
     def _prime_executor(self):