[Bugfix] Fix 307 Redirect for `/metrics` (#4523)

vllm/engine/metrics.py

@@ -119,7 +119,7 @@ class Metrics:
             buckets=[1, 2, 5, 10, 20],
         )
         self.counter_request_success = Counter(
-            name="vllm:request_success",
+            name="vllm:request_success_total",
             documentation="Count of successfully processed requests.",
             labelnames=labelnames + [Metrics.labelname_finish_reason])
 

vllm/entrypoints/openai/api_server.py

@@ -2,6 +2,7 @@ import asyncio
 import importlib
 import inspect
 import os
+import re
 from contextlib import asynccontextmanager
 from http import HTTPStatus
 
@@ -12,6 +13,7 @@ from fastapi.exceptions import RequestValidationError
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import JSONResponse, Response, StreamingResponse
 from prometheus_client import make_asgi_app
+from starlette.routing import Mount
 
 import vllm
 from vllm.engine.arg_utils import AsyncEngineArgs
@@ -55,8 +57,10 @@ def parse_args():
 
 
 # Add prometheus asgi middleware to route /metrics requests
-metrics_app = make_asgi_app()
-app.mount("/metrics", metrics_app)
+route = Mount("/metrics", make_asgi_app())
+# Workaround for 307 Redirect for /metrics
+route.path_regex = re.compile('^/metrics(?P<path>.*)$')
+app.routes.append(route)
 
 
 @app.exception_handler(RequestValidationError)