Prometheus metrics, health endpoints, request ids, logs, the diagnostics bundle, crash dumps and graceful shutdown. GET /metrics (text exposition format 0.0.4) is served on a separate listener, never on the API port, so the scraper never needs the API token. The listener answers nothing else. A port that is taken costs the metrics, not the server. No label carries SQL, user names, hosts or ids; routes are templates such as /api/connectors/:id/query. The series cover process memory and event-loop lag, HTTP requests and durations, the query admission lanes (active, queue depth, rejections, durations), engine worker restarts, scheduler runs, the audit queue and client-side errors.
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