Nesting FastAPI instances doesn't work very well about fastapi

[tiangolo]

There's something similar (but not the same) to handle those cases: APIRouter.

It also allows having the routes in different files. And it allows including routers with path prefixes that apply to all of them.

It wasn't properly documented, but it is now: https://fastapi.tiangolo.com/tutorial/bigger-applications/

E.g. a file at app/routers/users.py with:

from fastapi import APIRouter

router = APIRouter()


@router.get("/users/", tags=["users"])
async def read_users():
    return [{"username": "Foo"}, {"username": "Bar"}]

And a file at app/main.py with:

from fastapi import FastAPI

from .routers.users import router

app = FastAPI()

app.include_router(router)

It doesn't "mount" the route, but clones its routes. And the OpenAPI schema (and docs) end up together.

Does that work for your use case?

[kkinder]

Hey, thanks for the code example and suggestion.

Unfortunately it doesn't ft what I have in mind. The idea is to have two APIs each, with their own separate docs, OpenAPI files, etc, at different bases.

For example, you might have /public/* to serve /public/docs, /public/openapi.json, etc, for public use.

For internal use, you might have have /internal/* with the same set of resources. Essentially two FastAPI instances.

This could also be useful for doing something like versioning.

[haizaar]

@kkinder Can you share why do you want to server both public and internal stuff from the same instance? Isn't there a security contradiction?

[kkinder]

@haizaar No, that's not a security problem at all. Both APIs have access to the same database, same permissions, etc.

It's more that I don't want to expose methods I intend to change the signature of soon to potential end-users.

[haizaar]

@kkinder I see - so it's not internal (network-wise) API, but rather external API that serves both internal users and other users. If so, then I wonder why not having separate backends for those and route traffic to them using API GW? Should help with independent updates, etc.

[kkinder]

@haizaar Just more hassle. The model is the same, the authentication is the same, the middleware is the same, the update cycle is the same. I just want some methods listed on different swagger files, more or less.

[tiangolo]

Guys, this should be solved by PR #26 by @kabirkhan.

It is released as 0.4.0, the new docs are here: https://fastapi.tiangolo.com/tutorial/sub-applications-proxy/ 🎉 🚀

Let me know if it works for you.

---

As a side note, I think I tend to do the same as @haizaar, to set up different APIs in different backends (and different containers too), and then put them behind a load balancer (Traefik in my case).

But I also see how @kkinder's use case and others including having a reverse proxy make this feature relevant (so much there's another issue and this PR from above).

[tiangolo]

I guess this was solved. I'll close this issue now. But feel free to add more comments or create new issues.