Using the HTTPX client

Safir helps you manage a single httpx.AsyncClient for your application. Using a single HTTPX client improves performance by reusing connections.

Setting up the httpx.AsyncClient

The httpx.AsyncClient will be dyanmically created during application startup. Nothing further is needed apart from importing the dependency. However, it must be closed during application shutdown or a warning will be generated. This is normally done during the lifespan function for the FastAPI app.

from collections.abc import AsyncIterator
from contextlib import asynccontextmanager

from safir.dependencies.http_client import http_client_dependency


@asynccontextmanager
async def lifespan(app: FastAPI) -> AsyncIterator[None]:
    yield
    await http_client_dependency.aclose()


app = FastAPI(lifespan=lifespan)

You can add this line to an existing shutdown hook if you already have one.

Using the httpx.AsyncClient

To use the client in a handler, just request it via a FastAPI dependency:

from safir.dependencies.http_client import http_client_dependency


@routes.get("/")
async def get_index(
    http_client: httpx.AsyncClient = Depends(http_client_dependency),
) -> Dict[str, Any]:
    response = await http_client.get("https://keeper.lsst.codes")
    return await response.json()

Testing considerations

If you are using httpx.AsyncClient in your application tests as well, note that it will not trigger shutdown events, so if you trigger handlers that use the HTTP client, you will get a warning about an unclosed httpx.AsyncClient in your test output. To avoid this, wrap your test application in asgi_lifespan.LifespanManager from the asgi-lifespan Python package:

app = FastAPI()
async with LifespanManager(app):
    # insert tests here
    pass

You can do this in a fixture to avoid code duplication.