Clean scaffold of a Prometheus instance dedicated to fleet liveness, deliberately
separate from the home `prom` on PIHA. Scrapes only itself + the VPS-local
node_exporter for now.
- image pinned to prom/prometheus:v3.5.0 (LTS) — no :latest anti-pattern
- TSDB retention 15d / 2GB on the tight VPS; --web.enable-lifecycle for reloads
- mem_limit 512m, oom_score_adj +200 (sacrificial OOM victim before control-plane)
- tailscale-internal exposure via plain published 9090, mirroring control-plane
- node_exporter scraped via host.docker.internal:9100 (it runs network_mode: host)
- secret-free prometheus.yml; alerting/rule_files left as commented placeholders
- in-container healthcheck via busybox wget (present in the image; curl is not)
Smoke: docker compose config OK; promtool check config SUCCESS; up -d ->
/-/healthy + /-/ready OK; both targets (prometheus, fleet-node) report up.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
