# SDD Proposal: Prometheus Direct Charting (drop Grafana middleman)

**Change:** `prometheus-direct-charting`
**Phase:** proposal
**Date:** 2026-07-08

## 1. Problem / Why Now

Manage already does in-app charting — but indirectly. Today the only chart path is:

```
GrafanaChartWidget (recharts) ← GrafanaWidgetSource._fetch_chart
   ← POST {grafana}/api/ds/query  (datasource.type = "prometheus", hardcoded)
   ← Grafana proxies to Prometheus
```

Two problems with this:

1. **Grafana is a pure middleman.** The backend already hardcodes `datasource.type: "prometheus"` in every chart query. Grafana adds a hop, an API key, a different response shape (`/api/ds/query` frames), and a normalization layer — all to reach a Prometheus instance Manage could query directly via `/api/v1/query_range`. The existing `PrometheusWidgetSource` already proves Manage can talk to Prom straight; it just only does *instant* queries today.
2. **The project's documented rules are stale.** `openspec/config.yaml` says "Do NOT re-implement charting in-app" and "No recharts/d3 is in use." Both are already false in code: `recharts ^3.9.2` is declared and imported by `GrafanaChartWidget`. The config documents a reality the code left behind.

Meanwhile the operator wants two more metric visualizations Manage cannot currently render: a **gauge** and a **single value / mean-over-time** widget. Both belong naturally on the `prometheus` service, which today only exposes an instant-query numeric widget.

The clean answer is to stop routing charts through Grafana: query Prometheus directly, reuse the rendering infrastructure already written, add the two new modes, and remove the now-redundant Grafana surface.

## 2. Target Users and Situations

- **Primary users:** Homelab operators who want metric visualizations on the Manage dashboard without bouncing to Grafana for a quick glance.
- **Workflow moments:**
  - Glance at the dashboard: see a trend line, a gauge, or a mean value for a key PromQL query.
  - Build a custom at-a-glance panel from any PromQL expression Manage can already evaluate.
  - Decommission the Grafana hop for charts (one fewer external dependency in the chart path, one fewer API key to rotate).
- **Urgency:** Medium. Charts already work via Grafana today; this is a simplification plus two new widget modes, not an outage fix.

## 3. Product Outcome

After this change, an authenticated user can:

- Place a **Prometheus Chart** widget (line chart, multi-series) backed by a direct `/api/v1/query_range` call — same look as today's Grafana chart, no Grafana required.
- Place a **Prometheus Gauge** widget rendering an instant PromQL scalar as a gauge.
- Place a **Prometheus Mean** widget rendering a single value aggregated over a time window (e.g. `avg_over_time(...)`, or a query_range aggregate).
- Manage the dashboard without any Grafana service configured: the Grafana service type, link widget, chart widget, and status checks are removed.

## 4. Scope Boundaries and Non-Goals

### In scope

- **Direct Prometheus range query path** — backend hits `/api/v1/query_range` and returns the existing `{series:[{label,points}]}` shape so the frontend renderer is reused unchanged.
- **Shared series normalization** — extract the metric-label → readable-label logic currently inside `GrafanaWidgetSource._fetch_chart` into a reusable helper used by both the chart path and (where relevant) the new modes.
- **Rebrand + rebind** — `GrafanaChartWidget` → `PrometheusChartWidget`, moved from the `grafana` service to the `prometheus` service as the `chart` widget kind.
- **New `prometheus` widget kinds:** `gauge` and `mean` (semantics confirmed in the question round).
- **Grafana removal** — delete `integrations/grafana.py`, `GrafanaWidgetSource`, `GrafanaLinkWidget`, `get_grafana_status`, the ObservabilityPage Grafana section, both registries' `grafana` entries, nav entries, and their tests.
- **`config.yaml` rewrite** — replace the stale thin-dashboard / no-recharts wording with the reality: in-app charting via `recharts` is the sanctioned approach for Prometheus-backed series; Grafana is no longer referenced.
- **Migration note** — CHANGELOG entry: existing Grafana service instances must be deleted and recreated as Prometheus services (true data migration is impossible; different URLs).

### Non-goals (explicitly out of scope)

- **A general chart-widget framework with pluggable data-source middlewares.** Chart rendering is reused; data sources are not abstracted into a swappable adapter registry. Two concrete sources (Prometheus range query, and later the service-storage harness) are wired directly where needed.
- **Grafana datasource proxy for non-Prometheus sources** (Loki, InfluxDB, Postgres). If a real non-Prom need appears later, it is a separate change.
- **Embedding Grafana panels as images/iframes.** Grafana is removed, not embedded.
- **Editing PromQL in a rich editor** (autocomplete, metric explorer). Plain text input only, matching today's `prometheus_metric` widget.
- **qBittorrent widgets and the service-storage harness.** Those are a separate change (`service-storage-harness`); only the qBit speed widget *depends on* this change's chart capability.
- **Touching `prometheus_metric` (instant numeric widget).** It stays as-is; `mean` and `chart` are sibling kinds, not modes bolted onto it.
- **Re-indexing or migrating existing widget instance rows automatically.** Existing `grafana` `chart` widgets are orphaned by the removal and must be recreated as `prometheus` `chart` widgets by the operator (documented in CHANGELOG).

## 5. High-Level Approach

### 5.1 Backend

1. **Prometheus range query** — extend `PrometheusWidgetSource` (or add a sibling code path) to handle `widget_kind == "chart"`:
   - `GET {base_url}/api/v1/query_range?query=...&start=...&end=...&step=...`
   - Parse Prom `{value:[ts, val]}` matrix into the existing `{series:[{label, points}]}` shape.
2. **Shared normalization** — move the "metric labels → readable label" logic out of `GrafanaWidgetSource._fetch_chart` into `widgets/series.py` (or similar), so the Prom path and any future consumer reuse it.
3. **New kinds wiring** — `gauge` and `mean` resolve in `PrometheusWidgetSource.fetch`:
   - `gauge`: instant query (`/api/v1/query`), return `{value, threshold?, ...}` for a gauge renderer.
   - `mean`: range query aggregated to a single value (either PromQL `avg_over_time` via instant query, or client-side mean over a query_range window). Semantics decided in the question round.
4. **Integration update** — `integrations/prometheus.py` declares the three widget kinds (`metric`, `chart`, `gauge`, `mean`) with config schemas (`promql`, plus range params for `chart`/`mean`).
5. **Grafana removal** — delete `integrations/grafana.py`, drop `grafana` from `SERVICE_ADAPTERS`, `SERVICE_DEFINITIONS`, remove `_fetch_chart` and the Grafana link logic. Remove `get_grafana_status` from `routers/monitoring.py` and the Grafana branch from `ObservabilityPage`.
6. **`config.yaml` rewrite** — replace the stale charting rules with accurate wording.

### 5.2 Frontend

1. **Rebrand** — rename `GrafanaChartWidget.tsx` → `PrometheusChartWidget.tsx`; the recharts rendering (`LineChart`/`Line`/`XAxis`/`YAxis`/`Tooltip`/`mergeSeries`/`CHART_COLORS`) stays essentially unchanged.
2. **Registry** — in `integrations/registry.ts`, move `chart` to the `prometheus` binding and add `gauge` + `mean` bindings; delete the entire `grafana` binding.
3. **New components:**
   - `PrometheusGaugeWidget.tsx` — recharts `<RadialBarChart>` or a small SVG gauge; instant value.
   - `PrometheusMeanWidget.tsx` — single-value display (reuses `MetricCard`-style rendering) of the windowed mean.
4. **Nav + ObservabilityPage** — remove Grafana nav entries and the Grafana status card.
5. **Types** — `frontend/src/types/index.ts` drops Grafana status types; no new endpoint types (data still flows through `useWidgetData`).

### 5.3 Type contracts

- Backend: update `integrations/prometheus.py` widget-kind config models; remove Grafana models.
- Frontend: remove `GrafanaStatus` type; widget payloads stay `{series}` / `{value}` shaped.

## 6. Success Criteria / Acceptance Criteria

1. A user can configure a Prometheus service and place `chart`, `gauge`, `mean`, and `metric` widgets without any Grafana service present.
2. The `chart` widget renders multi-series line charts from `/api/v1/query_range` with the same look as the prior Grafana-backed chart.
3. The `gauge` widget renders an instant PromQL scalar as a gauge.
4. The `mean` widget renders a single value aggregated over the configured window.
5. No `grafana` references remain in `backend/src` or `frontend/src` (grep clean).
6. `openspec/config.yaml` no longer claims "no recharts" or "do not chart in-app"; its wording matches the implementation.
7. Existing `pytest`, `npm run build`, and `npm run lint` stay green; Grafana tests are removed, Prom chart/gauge/mean tests are added.
8. CHANGELOG documents the migration (delete Grafana services, recreate as Prometheus).

## 7. Risks and Mitigations

| Risk | Mitigation |
|------|------------|
| **Response-shape regression.** Prom `/api/v1/query_range` matrix differs from Grafana `/api/ds/query` frames. | Extract normalization into a shared helper; add a backend test that feeds a sample Prom range response and asserts the `{series}` shape the frontend already consumes. |
| **Orphaned configured widgets.** Existing `grafana/chart` widget rows break at render. | Acceptable + documented in CHANGELOG; the widget resolves to "unknown widget" gracefully (existing `WidgetInstance` error path). No silent data corruption. |
| **Gauge rendering complexity.** recharts gauges can be fiddly. | Constrain gauge to a single scalar + optional thresholds; if recharts gauge proves heavy, fall back to a ~50-line SVG gauge (contained, no new dep). |
| **Scope creep into a generic chart framework.** Tempting to abstract data sources. | Non-goal enforced: two direct wirings, no adapter registry. |
| **Stale docs/tests lingering.** | "No grafana references" acceptance criterion (grep) catches leftovers. |
| **Review budget (>400 lines).** | Slice into chained PRs (e.g. Slice 1: Prom range query + rebrand chart; Slice 2: gauge + mean; Slice 3: Grafana removal + config rewrite). Each slice leaves build/lint/test green. |
| **DataGrid migration (config rule callout).** | Not applicable — no DataGrid work here. The key technical risk is the response-shape regression above. |

## 8. Open Questions (for the proposal question round)

- **Q1 — `mean` semantics.** Default: client-side mean over a `query_range` window (e.g. last 1h, step 30s → average all returned values). Alternative: require the user to write `avg_over_time(...)` in the PromQL and just run an instant query. Which UX do you want?
- **Q2 — `gauge` thresholds.** Default: green/amber/red bands at user-configured thresholds (e.g. 70%/90%). Alternative: single color, no bands (simplest).
- **Q3 — Chart time window config.** Default: expose `from`/`to`/`step` (or a simpler "window" preset like 1h/6h/24h). Confirm the granularity users can configure.
- **Q4 — Multi-series on `mean`/`gauge`.** Default: single series only (one scalar). Confirm we do not try to render multi-series gauges.

## 9. Future Phases

1. **Service-storage harness integration** — the qBittorrent speed widget (separate `service-storage-harness` change) reuses this change's chart rendering with an in-service data source wired directly.
2. **Rich PromQL editing** — metric explorer / autocomplete.
3. **Non-Prom datasources** — only if a concrete need (Loki logs in-app) appears.
4. **Threshold-based alerting from chart widgets** — surface bands/lines from Alertmanager rules.
