FastAPI ^0.110 and on_event about prometheus-fastapi-instrumentator

[NiclasLindqvist]

I did it like this, seems to work fine

# Make a lifespan function that can do the .expose() that was previously done in the @app.on_event("startup")
@asynccontextmanager
async def lifespan(app: FastAPI):
    instrumentator.expose(app)
    yield

app = FastAPI(
    ...
    lifespan=lifespan,  # include the lifespan func in the FastAPI init call
)
instrumentator = Instrumentator().instrument(app)  # Initialize the instrumentator

[alegtk]

@NiclasLindqvist I confirm your assertion! Thank you for clearing my mistake.
Now I see what was the difference from our previous code to that on the manuals that is equivalent to your sample. One should instantiate the Instrumentator outside the lifespan coroutine. We were doing it all at once, instantianting and pipelining the expose method.
Maybe there is a drawback for some because the instrumentator object must be on the same scope as the coroutine. Perhaps one can solve this using FastAPI inherited state attribute as in

app = FastAPI(lifespan=...)
app.state.instr = Instrumentator(
        excluded_handlers=["/readiness", "/liveness", "/metrics"],
    ).instrument(app)