Lab: application lifecycle inside FastAPI¶

lifespan_api.py opens the report store in FastAPI lifespan. lifespan_worker.py repeats the resource and warmup wiring for a worker. Both versions correctly close the resource, including when startup fails. The duplication is the reason to consider a shared runtime once the service has several entrypoints.

check_lifespans.py asserts all four paths: successful HTTP request, successful worker report and a startup failure in each. HTTP uses FastAPI's TestClient; the worker stops via an asyncio.Event.

The instrumented ReportStore comes from the shared lifecycle lab. It is an in-memory database stand-in that checks resource lifetime, not a database client. Keep the neighbouring lab directory when copying these files.

Run from docs/blog/lab/2026-09-07-lifecycle-not-fastapi in the repository checkout:

uv run --no-project --python 3.13 --with-requirements requirements.txt python check_lifespans.py

Lab source on GitHub.