9. Disposability

Maximize robustness with fast startup and graceful shutdown.

• Disposable project means that the app is easy to deploy and start, and can be stopped at moment's notice (when they receive SIGTERM).
• Short startup time enable fast elastic scaling, rapid deployment of code or config changes, and robustness of production deploys.

Processes shut down gracefully when they receive a SIGTERM signal from the process manager and should be robust against sudden death in case of underlying hardware failure.

Lifespan Events

from contextlib import asynccontextmanager

from fastapi import FastAPI


def fake_answer_to_everything_ml_model(x: float):
    return x * 42


ml_models = {}


@asynccontextmanager
async def lifespan(app: FastAPI):
    # Load the ML model
    ml_models["answer_to_everything"] = fake_answer_to_everything_ml_model
    yield
    # Clean up the ML models and release the resources
    ml_models.clear()


app = FastAPI(lifespan=lifespan)


@app.get("/predict")
async def predict(x: float):
    result = ml_models["answer_to_everything"](x)
    return {"result": result}