Transactions not propagating from middleware

[tekumara]

Transactions are not propagating from middleware to the route in FastAPI applications using newer versions of uvicorn or uvloop. This results in the name of the middleware appearing in APM (eg: WebTransaction/Function/main:CanonicalLogMiddleware) rather than the route, and no tracing of the route itself.

The issue is present when using uvicorn>0.35.0 or uvloop>0.21.0. Possibly relevant changes are:

• uvicorn 0.36.0 Support custom IOLOOPs Kludex/uvicorn#2435
• uvloop 0.22.0 Fix build for Python 3.14 MagicStack/uvloop#638

A full repro is available at https://github.com/tekumara/newrelic-bug

[Newrelic-Boomi]

https://new-relic.atlassian.net/browse/NR-488558

[tekumara]

Last known good versions, where transactions are propagated:

uvicorn==0.35.0 uvloop==0.21.0

All of these version combinations fail to propagate the transaction:

uvicorn==0.35.0 uvloop==0.22.1

uvicorn==0.36.0 uvloop==0.21.0

uvicorn==0.38.0 uvloop==0.22.1

[TimPansino]

The issue is in uvicorn compatibility, they've changed to using asyncio.run(loop_factory=). This gap in support was recently discovered on our end, we've got a proposed fix already in #1576