Lab: why application lifecycle should not belong to FastAPI¶

The "before" half of the post: lifespan_api.py keeps the lifecycle in FastAPI's lifespan, and lifespan_worker.py is the worker for the same service, which has no lifespan and writes the same plumbing again. The "after" half is the one-lifecycle lab, where the API, a scheduler and the worker share one AppSpec.

uv venv --python 3.13 .venv
uv pip install --python .venv/bin/python fastapi "uvicorn[standard]"
.venv/bin/python lifespan_api.py 8000        # then SIGTERM it
.venv/bin/python lifespan_worker.py          # then SIGTERM it