Module metrics 

Prometheus metrics: install the global recorder once per process and serve GET /metrics for scraping. Real signals only — latency, escalations, what got served, what dropped.

Functions

handler

GET /metrics — render the current Prometheus scrape payload.

install

Install the global Prometheus recorder, once per process, and return a handle that renders the scrape payload. Safe to call more than once: OnceLock::get_or_init runs the install exactly once even under concurrent callers, so repeat calls (e.g. from every test that builds an crate::proxy::app) just reuse the cached handle instead of re-installing.