[QUESTION] aiohttp integration best practice

Description Hi. First of all great work with fastapi. I am currently evaluating shifting one of my api gateway from sanic / aiohttp to using fastapi / aiohttp. I have a bunch of microservices exposing various rest / grpc apis. The aim of the api gateway (with fast api) is to front all of them and provide a nice versioned, documented api contract. A typical api route can send requests to different endpoints and integrate results to formulate a nice response from the api gateway.

How can I […]?

• My questions revolve around best way to use aiohttp client within routes driven through an apirouter?
• Best way to initialize aiohttp ClientSession outside the routes as they provide a pool of tcp connections? There could be multiple clientSessions i.e. per type of microservice to provide consistency in timeouts dns behavior etc.
• Sessions should be initialized before app start. I see support for events i.e. @app.on_event("startup"). Is it possible to add those for every apirouter rather than the main app. If so how can clientSession objects be available inside routes to do request?

Is it possible to […]? If all of this is not supported what would be the best approach to move forward.

Additional context Add any other context or screenshots about the feature request here.

[wichert]

That is one way if you want create a new session for every request. You can also use a singleton approach:

class HttpClient:
    session: aiohttp.ClientSession = None

    def start(self):
        self.session = aiohttp.ClientSession()

    async def stop(self):
        await self.session.close()
        self.session = None

    def __call__(self) -> aiohttp.ClientSession:
        assert self.session is not None
        return self.session


http_client = HttpClient()

@app.on_event("startup")
async def startup():
    http_client.start()


@app.get("/fancy-path")
async def get_something(http_client: aiohttp.ClientSession = Depends(http_client)):
    r = await http_client.get("https://api.exampe.com")
    return r.json()

[raphaelauv]

Since I did not found any complete resource for that , I did a full example of :

fastAPI with an aiohttp client

full code and tests examples :

https://github.com/raphaelauv/fastAPI-aiohttp-example