[Frontend] add add_request_id middleware (#9594)

Signed-off-by: cjackal <44624812+cjackal@users.noreply.github.com>

vllm/entrypoints/openai/api_server.py

@@ -7,6 +7,7 @@ import re
 import signal
 import socket
 import tempfile
+import uuid
 from argparse import Namespace
 from contextlib import asynccontextmanager
 from functools import partial
@@ -475,6 +476,13 @@ def build_app(args: Namespace) -> FastAPI:
                                     status_code=401)
             return await call_next(request)
 
+    @app.middleware("http")
+    async def add_request_id(request: Request, call_next):
+        request_id = request.headers.get("X-Request-Id") or uuid.uuid4().hex
+        response = await call_next(request)
+        response.headers["X-Request-Id"] = request_id
+        return response
+
     for middleware in args.middleware:
         module_path, object_name = middleware.rsplit(".", 1)
         imported = getattr(importlib.import_module(module_path), object_name)