FastAPI multiple StreamRouters

[JoshJarabek7]

I'm struggling to get around the circular dependencies issue for FastAPI.

app.main - I create the faststream.rabbit.fastapi.RabbitRouter and I include it as a router for the app.

app.user.api - I can't import the router here, because these routes won't get included in app even though "include_router" happens. I can use the broker() function as a dependency, but that doesn't matter, because I still need a router. If I import the router from app.user.api to app.main then it's a circular dependency issue, because I'm using broker() as a dependency injection.

The only way I'm getting this to work is if I keep all my API routes on app.main.

Otherwise, they don't get included in the app's routes, or I receive a circular dependency.

I believe this creates a broker each time the RabbitRouter is initialized, if not, then that makes things easy and I can just use it as a regular APIRouter for FastAPI. I was looking through the codebase, and it looks like there might be a high-level abstraction to aio-pika's Connection class to potentially draw from as a Singleton? If I'm able to just declare the Connection in its own module and then implement the connection through the brokers and routers that would help!

Any tips or advice?

Thanks! This project rocks!

[Lancetnik]

As I understood you correct, you are trying to create broker in the same with FastAPI application file (app.main) and declare some handler in the other file. But you can create the broker in the same with handlers file (app.user.api) and just import it in the app.main

[Lancetnik]

@dimbler you are trying to get 2 different connections - it is the same case with multiple brokers. For now, FastStream doesn't support multiple brokers in the same time, but with FastAPI you can make it working.

Just create your custom lifespan to run both routers:

from contextlib import asynccontextmanager

@asynccontextmanager
async def run_both(app):
    async with (
        router_dest.lifespan_context(app),
        router_source.lifespan_context(app),
    ):
        yield
 
app = FastAPI(lifespan=run_both)

[dimbler]

@Lancetnik this is really brilliant decision. Thank you very much for assistance.
Probably this decision have to be in user guide.

[Lancetnik]

@dimbler I don't like this solution so much. It doesn't merge both routers AsyncAPI schema, so far it's just a trick.

[danielriegert]

@Lancetnik is this still the recommended / only option to use faststream to connect to multiple brokers?
I need to connect to two different vhosts on the same RabbitMQ instance. However, it seems that the vhost can only be specified at the RabbitBroker level so I would have to create two RabbitBroker instances and use FastAPI as a wrapper?

[Lancetnik]

@danielriegert unfortunately, yes
For now FastStream doesn't support multiple brokers (we are working on it) and RabbitBroker uses the only one connection to RMQ, so u can specify vhost only at broker level

[danielriegert]

@Lancetnik Thanks for clarifying. Is there already a tentative date / timeline for supporting multiple brokers?

[Lancetnik]

I already fixed the main problem in logging in 0.5.0, but AsyncAPI documentation generation is still a job to be done

You can track this issue: #526

This is not a prior task, so I thought to impelement it in the end of the year, but we can review our priorities if requested