Replaces the JSON history file behind /api/system/history with a fixed-size
binary ring buffer on disk and adds a second, downsampled tier so the chart
can now span seven days, not just twenty-four hours.
Two on-disk rings under frontend/data/system/:
metrics_ring_1m.bin 1440 pts @ 1 min ( 24 h)
metrics_ring_5m.bin 2016 pts @ 5 min ( 7 d)
Each point is 32 bytes (uint32 timestamp + 7 float32 metrics — cpu / mem /
swap / disk / load1 / net_rx / net_tx); files carry a 32-byte header with
magic, version, capacity, head, count, bucket seconds, and last bucket time
so they're self-describing and torn-write recoverable.
A persistent 1-minute ticker inside the backend (independent of whether
anyone's subscribed to /api/system/stream) composes points from /proc plus
the bash generator's latest snapshots and appends to the 1m ring; every
five minutes it averages the last five 1m points into the 5m ring. On
first run, the writer backfills the 1m ring from the legacy
metrics_history.json so first paint already has 24 h.
/api/system/history?range=N auto-selects the tier (≤1440 → 1m, else 5m),
keeps the existing { points, updated } shape, and additionally returns
`tier` for clients that care. Falls back to the legacy JSON on cold start.
Admin → System: 7d added to the range picker (now 1h / 6h / 24h / 7d),
swap + load1 promoted to their own trend cards, and every gauge / chart
card grows an Expand affordance that opens a fullscreen single-metric
deep-dive overlay:
- Big themed chart with grid, gradient area, peak/min/now markers, and
a live-pulsing "now" dot
- Hover crosshair + tooltip scrubs the series with formatted time +
value
- now / peak / avg / min stat strip with deltas
- Range picker (1h / 6h / 24h / 7d) re-fetches and re-themes per metric
- 1 Hz live SSE feed updates the overlay's now-stat in real time
- Escape / backdrop / close button all dismiss
- Per-metric accent colour (cpu=accent, mem=info, disk/swap=warning,
net_rx=success, net_tx=accent, load=accent) flows through gradient,
border, dot, and stats card
Zero new dependencies — hand-rolled SVG and pointer events throughout.
Signed-off-by: librelad <librelad@digitalangels.vip>
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