chore: import upstream snapshot with attribution

tests/utils/test_process_utils.py

@@ -0,0 +1,66 @@
+import os
+import uuid
+
+import pytest
+
+from mlflow.utils.os import is_windows
+from mlflow.utils.process import cache_return_value_per_process
+
+
+@cache_return_value_per_process
+def _gen_random_str1(v):
+    return str(v) + uuid.uuid4().hex
+
+
+@cache_return_value_per_process
+def _gen_random_str2(v):
+    return str(v) + uuid.uuid4().hex
+
+
+@cache_return_value_per_process
+def _gen_random_no_arg():
+    return uuid.uuid4().hex
+
+
+def test_cache_return_value_per_process():
+    path1 = _gen_random_str1(True)
+    path2 = _gen_random_str1(True)
+
+    assert path1 == path2
+
+    path3 = _gen_random_str1(False)
+    assert path3 != path2
+
+    no_arg_path1 = _gen_random_no_arg()
+    no_arg_path2 = _gen_random_no_arg()
+    assert no_arg_path1 == no_arg_path2
+
+    with pytest.raises(
+        ValueError,
+        match="The function decorated by `cache_return_value_per_process` is not allowed to be "
+        "called with key-word style arguments.",
+    ):
+        _gen_random_str1(v=True)
+
+    f2_path1 = _gen_random_str2(True)
+    f2_path2 = _gen_random_str2(False)
+
+    assert len({path1, path3, f2_path1, f2_path2}) == 4
+
+    # Skip the following block on Windows which doesn't support `os.fork`
+    if not is_windows():
+        # Use `os.fork()` to make parent and child processes share the same global variable
+        # `_per_process_value_cache_map`.
+        pid = os.fork()
+        if pid > 0:
+            # in parent process
+            child_pid = pid
+            # check child process exit with return value 0.
+            assert os.waitpid(child_pid, 0)[1] == 0
+        else:
+            # in forked out child process
+            child_path1 = _gen_random_str1(True)
+            child_path2 = _gen_random_str1(False)
+            test_pass = len({path1, path3, child_path1, child_path2}) == 4
+            # exit forked out child process with exit code representing testing pass or fail.
+            os._exit(0 if test_pass else 1)