infra/stacks/uptime-kuma/CONTEXT.md
Viktor Barzin 6dc77f4612
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uptime-kuma: add CONTEXT.md + ADR-0001 (intentionally lean; sizing/placement review)
Documents the 2026-06-13 right-sizing review: Kuma is already lean (~1 check/s, 227 monitors mostly at 300s, 77MB on shared MySQL, 30d retention); the 'scraping too much' concern traced to a fixed socket.io login-timeout incident, not load. Records the deliberate decisions (keep per-service [External] monitors over canaries; keep datastore on shared mysql.dbaas) with rejected alternatives + rationale, plus the known internal-sync no-prune gap (stale Goldilocks monitor cleaned up by hand).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-14 09:11:22 +00:00

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Markdown

# Uptime Kuma — Context
Glossary for the uptime-kuma monitoring context. Terms only — no implementation
detail. Decisions live in `docs/adr/`.
## Glossary
**Active check (poll)** — Uptime Kuma actively probes a target on an interval
(HTTP / TCP / ping / DB). This is *polling*, not "scraping." Prometheus *scrapes*
exporters; Kuma *polls* targets. (Note: Prometheus does **not** scrape Kuma — a
separate monitoring lane.)
**Monitor** — one configured target plus its check definition.
**Internal monitor** — probes a service on its in-cluster address
(`*.svc.cluster.local`). Answers "is the service itself healthy?"
**`[External]` monitor** — probes a service via its full public path
(DNS → Cloudflare → cloudflared tunnel → Traefik). Answers "is the service
reachable the way users reach it?" Maintained one-per-externally-reachable-service
by deliberate choice (see ADR-0001).
**Heartbeat** — one recorded check result (up/down + latency), persisted to the
datastore.
**External-access divergence** — the condition where a service is healthy
*internally* but its `[External]` path is down — i.e. the shared
Cloudflare/tunnel/Traefik path is broken while the service itself is fine.
Surfaced by the `ExternalAccessDivergence` alert.