Describe your environment

OS: macOS
Python version: 3.12.7
Package version: v0.51b0

What happened?

When instrumenting a FastAPI/Starlette app which uses Host-based routing (ref: https://www.starlette.io/routing/#host-based-routing), the instrument fails with the following error:

  File "/Users/fvoron/Development/polar/server/.venv/lib/python3.12/site-packages/opentelemetry/instrumentation/fastapi/__init__.py", line 427, in _get_route_details
    route = starlette_route.path
            ^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Host' object has no attribute 'path'

Steps to Reproduce

Create the following Starlette app:

# app.py
from opentelemetry.instrumentation.starlette import StarletteInstrumentor
from starlette import applications
from starlette.routing import Host, Router

app = applications.Starlette(
    routes=[
        Host("127.0.0.1", Router()),
    ]
)
StarletteInstrumentor.instrument_app(app)

Run it:

uvicorn app:app

Make an HTTP request:

curl http://127.0.0.1:8000

Expected Result

The request should be processed without error.

Actual Result

The request triggers an exception.

Additional context

A similar issue was reported and recently fixed on Sentry: getsentry/sentry-python#2631

The fix involved to fallback to the scope path when the path attribute was not directly available on the route object: https://github.com/getsentry/sentry-python/pull/4157/files

Would you like to implement a fix?

Yes