• I have looked for existing issues (including closed) about this

Bug Report

I am looking at the example code for setting up prometheus metrics in https://github.com/tokio-rs/axum/blob/main/examples/prometheus-metrics/src/main.rs. It creates a handle like so:

Reading the docs for https://docs.rs/metrics-exporter-prometheus/latest/metrics_exporter_prometheus/#upkeep-and-maintenance it states

However, when using lower-level builder methods PrometheusBuilder::build_recorder or PrometheusBuilder::install_recorder, this upkeep task is not spawned automatically. Users are responsible for keeping a handle to the recorder (PrometheusHandle) and calling the run_upkeep method at a regular interval.

I see no calls to run_upkeep() in the example code, is this something that should be added? From looking at upstream code it seems this is done like so:
https://docs.rs/metrics-exporter-prometheus/latest/src/metrics_exporter_prometheus/exporter/builder.rs.html#472-478:

let recorder_handle = handle.clone();
        tokio::spawn(async move {
            loop {
                tokio::time::sleep(upkeep_timeout).await;
                recorder_handle.run_upkeep();
            }
        });

Version

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