add prometheus metrics endpoints via helper package (#4436)

* add prometheus metrics endpoints via helper package

* model server specific requirements

* mark as public endpoint

---------

Co-authored-by: Richard Kuo (Onyx) <[email protected]>

Author: rkuo-danswer

backend/model_server/main.py

@@ -9,6 +9,7 @@
 import torch
 import uvicorn
 from fastapi import FastAPI
+from prometheus_fastapi_instrumentator import Instrumentator
 from sentry_sdk.integrations.fastapi import FastApiIntegration
 from sentry_sdk.integrations.starlette import StarletteIntegration
 from transformers import logging as transformer_logging  # type:ignore
@@ -127,6 +128,9 @@ def get_model_app() -> FastAPI:
 
     add_onyx_request_id_middleware(application, request_id_prefix, logger)
 
+    # Initialize and instrument the app
+    Instrumentator().instrument(application).expose(application)
+
     return application
 
 

backend/onyx/main.py

@@ -17,6 +17,7 @@
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import JSONResponse
 from httpx_oauth.clients.google import GoogleOAuth2
+from prometheus_fastapi_instrumentator import Instrumentator
 from sentry_sdk.integrations.fastapi import FastApiIntegration
 from sentry_sdk.integrations.starlette import StarletteIntegration
 from sqlalchemy.orm import Session
@@ -435,6 +436,9 @@ def get_application() -> FastAPI:
     # Ensure all routes have auth enabled or are explicitly marked as public
     check_router_auth(application)
 
+    # Initialize and instrument the app
+    Instrumentator().instrument(application).expose(application)
+
     return application
 
 

backend/onyx/server/auth_check.py

@@ -49,6 +49,7 @@
     ("/auth/oauth/callback", {"GET"}),
     # anonymous user on cloud
     ("/tenants/anonymous-user", {"POST"}),
+    ("/metrics", {"GET"}),  # added by prometheus_fastapi_instrumentator
 ]
 
 

backend/requirements/default.txt

@@ -96,3 +96,4 @@ mistune==0.8.4
 sentry-sdk==2.14.0
 prometheus_client==0.21.0
 fastapi-limiter==0.1.6
+prometheus_fastapi_instrumentator==7.1.0

backend/requirements/model_server.txt

@@ -15,4 +15,5 @@ uvicorn==0.21.1
 voyageai==0.2.3
 litellm==1.61.16
 sentry-sdk[fastapi,celery,starlette]==2.14.0
-aioboto3==13.4.0
+aioboto3==13.4.0
+prometheus_fastapi_instrumentator==7.1.0