[Bugfix][Frontend] Fix missing `/metrics` endpoint (#6463)

tests/entrypoints/openai/test_basic.py

+from http import HTTPStatus
+
+import openai
+import pytest
+import requests
+
+from vllm.version import __version__ as VLLM_VERSION
+
+from ...utils import RemoteOpenAIServer
+
+MODEL_NAME = "HuggingFaceH4/zephyr-7b-beta"
+
+
+@pytest.fixture(scope="module")
+def server():
+    args = [
+        # use half precision for speed and memory savings in CI environment
+        "--dtype",
+        "bfloat16",
+        "--max-model-len",
+        "8192",
+        "--enforce-eager",
+        "--max-num-seqs",
+        "128",
+    ]
+
+    with RemoteOpenAIServer(MODEL_NAME, args) as remote_server:
+        yield remote_server
+
+
+@pytest.fixture(scope="module")
+def client(server):
+    return server.get_async_client()
+
+
+@pytest.mark.asyncio
+async def test_show_version(client: openai.AsyncOpenAI):
+    base_url = str(client.base_url)[:-3].strip("/")
+
+    response = requests.get(base_url + "/version")
+    response.raise_for_status()
+
+    assert response.json() == {"version": VLLM_VERSION}
+
+
+@pytest.mark.asyncio
+async def test_check_health(client: openai.AsyncOpenAI):
+    base_url = str(client.base_url)[:-3].strip("/")
+
+    response = requests.get(base_url + "/health")
+
+    assert response.status_code == HTTPStatus.OK
+
+
+@pytest.mark.asyncio
+async def test_log_metrics(client: openai.AsyncOpenAI):
+    base_url = str(client.base_url)[:-3].strip("/")
+
+    response = requests.get(base_url + "/metrics")
+
+    assert response.status_code == HTTPStatus.OK

vllm/entrypoints/openai/api_server.py

@@ -73,11 +73,13 @@ async def lifespan(app: fastapi.FastAPI):
 
 router = APIRouter()
 
-# Add prometheus asgi middleware to route /metrics requests
-route = Mount("/metrics", make_asgi_app())
-# Workaround for 307 Redirect for /metrics
-route.path_regex = re.compile('^/metrics(?P<path>.*)$')
-router.routes.append(route)
+
+def mount_metrics(app: fastapi.FastAPI):
+    # Add prometheus asgi middleware to route /metrics requests
+    metrics_route = Mount("/metrics", make_asgi_app())
+    # Workaround for 307 Redirect for /metrics
+    metrics_route.path_regex = re.compile('^/metrics(?P<path>.*)$')
+    app.routes.append(metrics_route)
 
 
 @router.get("/health")
@@ -167,6 +169,8 @@ def build_app(args):
     app.include_router(router)
     app.root_path = args.root_path
 
+    mount_metrics(app)
+
     app.add_middleware(
         CORSMiddleware,
         allow_origins=args.allowed_origins,