Backport thread_name_prefix from upstream

CHANGES

@@ -1,3 +1,10 @@
+Unreleased
+==========
+
+- The ThreadPoolExecutor class constructor now accepts an optional ``thread_name_prefix``
+  argument to make it possible to customize the names of the threads created by the pool.
+  Upstream contribution by Gregory P. Smith in https://bugs.python.org/issue27664. 
+
 3.1.1
 =====
 

concurrent/futures/thread.py

@@ -5,6 +5,7 @@
 
 import atexit
 from concurrent.futures import _base
+import itertools
 import Queue as queue
 import threading
 import weakref
@@ -90,12 +91,17 @@ def _worker(executor_reference, work_queue):
 
 
 class ThreadPoolExecutor(_base.Executor):
-    def __init__(self, max_workers=None):
+
+    # 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=''):
         """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.
         """
         if max_workers is None:
             # Use this number because ThreadPoolExecutor is often
@@ -109,6 +115,8 @@ def __init__(self, max_workers=None):
         self._threads = set()
         self._shutdown = False
         self._shutdown_lock = threading.Lock()
+        self._thread_name_prefix = (thread_name_prefix or
+                                    ("ThreadPoolExecutor-%d" % self._counter()))
 
     def submit(self, fn, *args, **kwargs):
         with self._shutdown_lock:
@@ -130,8 +138,11 @@ def weakref_cb(_, q=self._work_queue):
             q.put(None)
         # 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,
+        num_threads = len(self._threads)
+        if num_threads < self._max_workers:
+            thread_name = '%s_%d' % (self._thread_name_prefix or self,
+                                     num_threads)
+            t = threading.Thread(name=thread_name, target=_worker,
                                  args=(weakref.ref(self, weakref_cb),
                                        self._work_queue))
             t.daemon = True

test_futures.py

@@ -29,7 +29,7 @@ def reap_threads(func):
     If threading is unavailable this function does nothing.
     """
     @functools.wraps(func)
-    def decorator(*args): 
+    def decorator(*args):
         key = test_support.threading_setup()
         try:
             return func(*args)
@@ -50,7 +50,7 @@ def _assert_python(expected_success, *args, **env_vars):
     # caller is responsible to pass the full environment.
     if env_vars.pop('__cleanenv', None):
         env = {}
-    env.update(env_vars) 
+    env.update(env_vars)
     cmd_line.extend(args)
     p = subprocess.Popen(cmd_line, stdin=subprocess.PIPE,
                          stdout=subprocess.PIPE, stderr=subprocess.PIPE,
@@ -78,7 +78,7 @@ def assert_python_ok(*args, **env_vars):
     return _assert_python(True, *args, **env_vars)
 
 
-def strip_python_stderr(stderr): 
+def strip_python_stderr(stderr):
     """Strip the stderr of a Python process from potential debug output
     emitted by the interpreter.
 
@@ -230,6 +230,29 @@ def test_del_shutdown(self):
         for t in threads:
             t.join()
 
+    def test_thread_names_assigned(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.assertRegexpMatches(t.name, r'^SpecialPool_[0-4]$')
+            t.join()
+
+    def test_thread_names_default(self):
+        executor = futures.ThreadPoolExecutor(max_workers=5)
+        executor.map(abs, range(-5, 5))
+        threads = executor._threads
+        del executor
+
+        for t in threads:
+            # Ensure that our default name is reasonably sane and unique when
+            # no thread_name_prefix was supplied.
+            self.assertRegexpMatches(t.name, r'ThreadPoolExecutor-\d+_[0-4]$')
+            t.join()
+
 
 class ProcessPoolShutdownTest(ProcessPoolMixin, ExecutorShutdownTest):
     def _prime_executor(self):