Generate _ModelInfo properties file when loading to improve loading speed (#23558)

Signed-off-by: Manoel Marques <manoel.marques@ibm.com>
Signed-off-by: Manoel Marques <manoelmrqs@gmail.com>
Co-authored-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>
Co-authored-by: Luka Govedič <ProExpertProg@users.noreply.github.com>

vllm/model_executor/model_loader/weight_utils.py

@@ -11,6 +11,7 @@ import tempfile
 import time
 from collections import defaultdict
 from collections.abc import Generator
+from contextlib import contextmanager
 from pathlib import Path
 from typing import Any, Callable, Optional, Union
 
@@ -98,6 +99,49 @@ def get_lock(model_name_or_path: Union[str, Path],
     return lock
 
 
+@contextmanager
+def atomic_writer(filepath: Union[str, Path],
+                  mode: str = 'w',
+                  encoding: Optional[str] = None):
+    """
+    Context manager that provides an atomic file writing routine.
+
+    The context manager writes to a temporary file and, if successful,
+    atomically replaces the original file.
+
+    Args:
+        filepath (str or Path): The path to the file to write.
+        mode (str): The file mode for the temporary file (e.g., 'w', 'wb').
+        encoding (str): The encoding for text mode.
+
+    Yields:
+        file object: A handle to the temporary file.
+    """
+    # Create a temporary file in the same directory as the target file
+    # to ensure it's on the same filesystem for an atomic replace.
+    temp_dir = os.path.dirname(filepath)
+    temp_fd, temp_path = tempfile.mkstemp(dir=temp_dir)
+
+    try:
+        # Open the temporary file for writing
+        with os.fdopen(temp_fd, mode=mode, encoding=encoding) as temp_file:
+            yield temp_file
+
+        # If the 'with' block completes successfully,
+        # perform the atomic replace.
+        os.replace(temp_path, filepath)
+
+    except Exception:
+        logger.exception(
+            "Error during atomic write. Original file '%s' not modified",
+            filepath)
+        raise
+    finally:
+        # Clean up the temporary file if it still exists.
+        if os.path.exists(temp_path):
+            os.remove(temp_path)
+
+
 def maybe_download_from_modelscope(
         model: str,
         revision: Optional[str] = None,