telemetry: per-cluster usage history
Keep one compact sample per cluster per UTC day (disk bytes, volume
count, volume servers), retained for -max-age and persisted in the
state file. Serve it at /api/history?cluster_id=...&days=90 and add a
per-cluster lookup with disk/volume charts to the built-in dashboard.
* telemetry: persist server state across restarts
The telemetry server kept the instance map and Prometheus gauges only
in process memory, so every deploy or restart reset all collected
metrics until clusters re-reported over the next 24h.
Snapshot the instance map to a JSON state file (atomic tmp+rename) on
a debounced interval and on SIGTERM, and restore it on startup,
preserving received_at so the cleanup and active-cluster windows stay
correct. Defaults to data/telemetry-state.json, which the deployed
systemd unit's WorkingDirectory already provides; -state-file=''
disables.
* telemetry: keep instances for 90 days by default
With state now persisted across restarts, a longer retention default is
meaningful; raise -max-age from 30 to 90 days so per-cluster data
survives long enough for quarterly views.
Chris LuandGitHub