Name Python threads. (#2767)

python/ray/import_thread.py

@@ -35,7 +35,7 @@ class ImportThread(object):
 
     def start(self):
         """Start the import thread."""
-        t = threading.Thread(target=self._run)
+        t = threading.Thread(target=self._run, name="ray_import_thread")
         # Making the thread a daemon causes it to exit
         # when the main thread exits.
         t.daemon = True

python/ray/profiling.py

@@ -87,7 +87,9 @@ class Profiler(object):
         self.lock = threading.Lock()
 
     def start_flush_thread(self):
-        t = threading.Thread(target=self._periodically_flush_profile_events)
+        t = threading.Thread(
+            target=self._periodically_flush_profile_events,
+            name="ray_push_profiling_information")
         # Making the thread a daemon causes it to exit when the main thread
         # exits.
         t.daemon = True

python/ray/worker.py

@@ -2259,10 +2259,15 @@ def connect(info,
     # scheduler for new error messages.
     if mode == SCRIPT_MODE:
         if not worker.use_raylet:
-            t = threading.Thread(target=print_error_messages, args=(worker, ))
+            t = threading.Thread(
+                target=print_error_messages,
+                name="ray_print_error_messages",
+                args=(worker, ))
         else:
             t = threading.Thread(
-                target=print_error_messages_raylet, args=(worker, ))
+                target=print_error_messages_raylet,
+                name="ray_print_error_messages",
+                args=(worker, ))
         # Making the thread a daemon causes it to exit when the main thread
         # exits.
         t.daemon = True