Fix flaky compute_world_size test on devservers and make pyre happy

Differential Revision: D71576534

Pull Request resolved: #1030

Author: kiukchung

torchx/examples/apps/compute_world_size/config/__init__.py

@@ -0,0 +1,5 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.

torchx/examples/apps/compute_world_size/module/test/util_test.py

@@ -26,8 +26,8 @@ def test_compute_world_size(self) -> None:
                     "rank": 0,
                     "world_size": 1,
                     "master_addr": "localhost",
-                    # ephemeral port range in linux
-                    "master_port": random.randint(32768, 60999),
+                    # specifying 0 as master_port makes TCPStore chose a free random port
+                    "master_port": 0,
                     "backend": "gloo",
                 }
             }