Organising larger applications

[aminalaee]

Hey,
First off I wanted to thank you for the great library and the effort behind it.

This might be more of a question than an issue,
Based on the examples I've seen in the docs we pass the whole application inside the Mangum adapter. Like:

from fastapi import FastAPI
from mangum import Mangum

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}

handler = Mangum(app)

Well this is one convention and works for some projects. For larger projects it makes sense to split the backend into services/functions and let the Lambda scale each separately as explained in the AWS docs here.

I think this should be straightforward with Starlette Router or FastAPI APIRouter instances which are basically mini ASGI applications.
So maybe something like this should work out of the box:

# One handler per router
from fastapi import APIRouter
from mangum import Mangum

router = APIRouter()

@router.get("/")
def read_root():
    return {"Hello": "World"}

handler = Mangum(router)

And another handler for another router.
So my question is if this makes sense or I am missing something?
And if this is supported maybe there can be examples or tests demonstrating this?

[jordaneremieff]

Hi @aminalaee,

To my knowledge the APIRouter class in fastapi subclassess the Router in starlette. Based on this, it would appear that this class exposes an ASGI-compatible interface (see also), so the usage you are suggesting should work.

There is currently an open issue related to improving the documentation and adding more examples, so I'm happy to merge any PRs that provide any framework-specific examples demonstrating things like this.

[aminalaee]

To my knowledge the APIRouter class in fastapi subclassess the Router in starlette. Based on this, it would appear that this class exposes an ASGI-compatible interface (see also), so the usage you are suggesting should work.

Yes, as far as I know this should be ok.

There is currently an open issue related to improving the documentation and adding more examples, so I'm happy to merge any PRs that provide any framework-specific examples demonstrating things like this.

Great, I'll add some docs so we can discuss this.

[aminalaee]

I have written a small blog about this https://aminalaee.dev/posts/2022/fastapi-aws-lambda/#larger-applications if this is useful I can add the related info to Mangum docs too. Please let me know @jordaneremieff

[jordaneremieff]

@aminalaee that's great, I think it would be a useful addition to https://mangum.io/external-links/ if you would like to PR a link and brief description.