"Behind a Proxy" changed behaviour in the new version 0.109.0

[neugeeug]

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Example Code

uvicorn rest.main:server --host 0.0.0.0 --port 8080 --reload --root-path /proxy

server = FastAPI()

# separate spec at /v1/docs
server.mount("/v1", app_v1)
# separate spec at /v2/docs
server.mount("/v2", app_v2)

#where app_v1, app_v2 is like below
app_v1 = FastAPI(openapi_tags=tags_metadata, title="Pet store")

Description

When I run the uvicorn with the --root-path option for the above setup, the server is expecting that I include the defined root path in every request e.g:
http://localhost:8080/v2/docs is not working (404)
http://localhost:8080/proxy/v2/docs is working

IN version 0.108.0 It works as described here https://fastapi.tiangolo.com/advanced/behind-a-proxy/

Operating System

Linux

Operating System Details

No response

FastAPI Version

0.109.0

Pydantic Version

2.5.3

Python Version

3.11.5

Additional Context

No response

[abramjstamper]

I updated yesterday to 0.109.0 and ran into the same issue today.

uvicorn app:main --host 0.0.0.0 --port 80 --root-path "/test"

router = APIRouter(prefix="/test")
@router.get("/")
async def test():
    return "will 404"

@router.get("/test123")
async def test():
    return "will 404"

router_alt = APIRouter()
@router.get("/test")
async def test():
    return "will 404"

app = FastAPI()
app.include_router(router)
app.include_router(router_alt)

Even though the requests aren't working correctly, they render correctly in the swagger docs. It seems anything that has the same leading characters as --root-path fails. Setting path_prefix instead of --root-path doesn't seem to make any difference either.

I believe this regression was introduced in starlette v0.35.0 with this PR.

[mawiegand]

I also had an issue with it as described here: #10798 (comment)

[andy-5]

I have exactly the same issue with 0.109.0 (and starlette 0.35.1). It seems --root-path together with sub-applications is broken.

To reproduce, i used the simple example from https://fastapi.tiangolo.com/advanced/sub-applications/ and started it with

uvicorn main:app --root-path /api/v1

as explained in https://fastapi.tiangolo.com/advanced/behind-a-proxy/ .

Accessing http://127.0.0.1:9999/api/v1/subapi/sub through the example Traefik setup, or directly accessing http://127.0.0.1:8000/subapi/sub results in 404.

It works fine with FastAPI 0.108.0.

[tiangolo]

Thank you! Indeed, this is an issue, it's because recently Starlette was updated to more strictly follow the ASGI specification, and now, since versions 0.34.0 and 0.35.0 it is more correct, nevertheless, Uvicorn needs the same/equivalent change.

Uvicorn has an ongoing PR here: #10978

Once that is taken and there's a new release including it, that will be solved. As a temporary workaround, you can pin FastAPI to a previous version (that depended on a previous version of Starlette), or you might try Hypercorn.

I created an issue to track this here: #10978

[neugeeug]

Thank you !