fixing stress test failure (#164353)

Summary: This diff fixes a stress test failure by adding a new binary echo4.py and modifying the existing echo1.py binary. The changes are made in both fbcode and xplat directories. The api_test.py file is updated to use the new echo4.py binary, and the BUCK file is updated to include the new binary.

Test Plan:
```
buck test -j 18 'fbcode//mode/opt' fbcode//caffe2/test/distributed/elastic/multiprocessing:api_test -- --exact 'caffe2/test/distributed/elastic/multiprocessing:api_test - test_binary_redirect_and_tee (api_test.StartProcessesListAsBinaryTest)' --run-disabled --stress-runs 20 --record-results
```

```
buck test -j 18 'fbcode//mode/opt' fbcode//caffe2/test/distributed/elastic/multiprocessing:api_test -- --exact 'caffe2/test/distributed/elastic/multiprocessing:api_test - test_binary (api_test.StartProcessesListAsBinaryTest)' --run-disabled --stress-runs 20 --record-results
```

https://www.internalfb.com/intern/testinfra/testrun/17732923648474906

https://www.internalfb.com/intern/testinfra/testrun/15481123834815653

Differential Revision: D83623694

Pull Request resolved: https://github.com/pytorch/pytorch/pull/164353
Approved by: https://github.com/d4l3k

test/distributed/elastic/multiprocessing/api_test.py

@@ -559,7 +559,7 @@ if not (TEST_WITH_DEV_DBG_ASAN or IS_WINDOWS or IS_MACOS):
             FAIL = 138
             pc = start_processes(
                 name="echo",
-                entrypoint=bin("echo1.py"),
+                entrypoint=bin("echo4.py"),
                 args={0: ("--exitcode", FAIL, "foo"), 1: ("--exitcode", 0, "bar")},
                 envs={0: {"RANK": "0"}, 1: {"RANK": "1"}},
                 logs_specs=DefaultLogsSpecs(

test/distributed/elastic/multiprocessing/bin/echo1.py

@@ -9,7 +9,6 @@
 import argparse
 import os
 import sys
-import time
 
 
 if __name__ == "__main__":
@@ -24,6 +23,5 @@ if __name__ == "__main__":
         print(f"exit {exitcode} from {rank}", file=sys.stderr)
         sys.exit(exitcode)
     else:
-        time.sleep(1000)
         print(f"{args.msg} stdout from {rank}")
         print(f"{args.msg} stderr from {rank}", file=sys.stderr)

test/distributed/elastic/multiprocessing/bin/echo4.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python3
+
+# Copyright (c) Facebook, Inc. and its 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.
+
+import argparse
+import os
+import sys
+import time
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="test binary, exits with exitcode")
+    parser.add_argument("--exitcode", type=int, default=0)
+    parser.add_argument("msg", type=str)
+    args = parser.parse_args()
+
+    rank = int(os.environ["RANK"])
+    exitcode = args.exitcode
+    if exitcode != 0:
+        print(f"exit {exitcode} from {rank}", file=sys.stderr)
+        sys.exit(exitcode)
+    else:
+        time.sleep(1000)
+        print(f"{args.msg} stdout from {rank}")
+        print(f"{args.msg} stderr from {rank}", file=sys.stderr)