Module observability 

Available on crate feature metrics only.

A Prometheus implementation of the Observer trait.

Gated behind metrics. This is the adapter that re-creates stream-center’s old behaviour — but as an injected observer the host opts into, not a global singleton the engine reaches for. The engine core never depends on prometheus.

Structs

PrometheusObserver

Prometheus-backed Observer. Construct it, register it on the engine builder, and expose its registry on your /metrics endpoint.