Cairn instrument

Cairn is a self-hosted observability stack. One Rust ingest service writes logs, traces, metrics, browser events, errors, and payment facts into TimescaleDB. Grafana is the only UI. There is no Cairn UI, no query API, no admin daemon.

This skill covers what is true because of how Cairn is built. It assumes you already know OpenTelemetry, Grafana, and SQL.

How it fits together

One project is one product. Every fact row carries (project_id, source_id), resolved server-side from the credential. The client body never decides ownership.

Sources have a kind: browser, collector, sentry, stripe, or adapter. A key belongs to one source. Browser keys are public and revocable. Adapter keys stay on private networks. Stripe authenticates by signature, not by key.

Grafana connects as cairn_grafana and reads through cairn_ui.* contracts and safe views. It cannot see key digests or raw payment payloads.

Every route commits before it answers 2xx. Delivery is at-least-once with stable retry keys, so a retried batch is a no-op rather than a double count.

Routes