Cannot reach load docs - openapi spec not found (swagger/redoc) when using root_path and no proxy

[adamcunnington]

First check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn't find it.
• I searched the FastAPI documentation, with the integrated search.
• I already searched in Google "How to X in FastAPI" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to FastAPI but to Pydantic.
• I already checked if it is not related to FastAPI but to Swagger UI.
• I already checked if it is not related to FastAPI but to ReDoc.
• After submitting this, I commit to one of:
  • Read open issues with questions until I find 2 issues where I can help someone and add a comment to help there.
  • I already hit the "watch" button in this repository to receive notifications and I commit to help at least 2 people that ask questions in the future.
  • Implement a Pull Request for a confirmed bug.

Example

Here's a self-contained, minimal, reproducible, example with my use case:

import fastapi


api = fastapi.FastAPI(root_path="/api")
router = fastapi.APIRouter()
api.include_router(router, prefix="/v1")

uvicorn main:api --reload --debug

Description

• Open the browser and call the endpoint /docs.
• It returns the swagger doc but with an error, "Not Found /api/openapi.json"
• I see in my terminal 2 requests, the second being a call from swagger.

INFO:     127.0.0.1:43074 - "GET /api/docs HTTP/1.1" 200 OK
INFO:     127.0.0.1:43074 - "GET /api/api/openapi.json HTTP/1.1" 404 Not Found

The docs pre-empts this problem here but doesn't suggest a fix beyond the assumption that the reason for root_path usage is that a proxy is involved. What about the normal use case of serving the api under some common prefix, without a proxy in front?

[adamcunnington]

@Kludex is aware

[Mause]

As you've found, root_path is specifically for when your api is being served behind a proxy. If you just want to prefix it, have it be a router mounted at a prefix

[adamcunnington]

Yarp, thanks. You can't set a prefix on the application's base router - maybe that can be changed?
For now, I am doing this:

import fastapi


api = fastapi.FastAPI()
api.router.prefix = "/api"
router = fastapi.APIRouter()
api.include_router(router, prefix="/v1")

[adamcunnington]

@Bluenix2 provided a fix for this in this PR; #2950

[ycd]

I don't see any bug to fix, this is the expected behaviour, this could be a feature request, that being said, i'm not sure the provided PR is going to be accepted though.

[tiangolo]

Thanks for the help here @Mause and @ycd ! 👏 🙇

Yep, this would be the right solution:

from fastapi import FastAPI, APIRouter

# Do not add path operations to the app directly
app = FastAPI()
# Add the top level path operations to the top_router
top_router = APIRouter(prefix="/api")
sub_router = APIRouter(prefix="/v1")
top_router.include_router(sub_router)
app.include_router(top_router)

It's quite a corner case, so it wouldn't really make much sense to have it as part of FastAPI itself at the top level and add another keyword argument.

---

If that solves the original problem, then you can close this issue ✔️

Sorry for the long delay! 🙈 I wanted to personally address each issue/PR and they piled up through time, but now I'm checking each one in order.

[github-actions]

Assuming the original need was handled, this will be automatically closed now. But feel free to add more comments or create new issues or PRs.