# Prometheus Charting

> Domain: `prometheus-charting` · **Canonical specification.** Created by `prometheus-direct-charting`;
> transport model modified by `grafana-metric-gateway` (Grafana gateway is the sanctioned
> `prometheus` query path; chart/gauge/mean widget components renamed to neutral `Metric*`).
>
> This is the merged end-state of Manage's metric-visualization surface. The `prometheus` service is
> the sole metric surface; its `chart` / `gauge` / `mean` / `metric` widget queries route through a
> **Grafana gateway** (`POST {grafana_url}/api/ds/query`) — Prometheus remains the logical source,
> Grafana is the transport. In-app charting via `recharts` is the sanctioned renderer; no `grafana`
> *service type* (or its widgets/status/UI surfaces) is reintroduced; orphaned Grafana widget
> instances degrade gracefully; and operators reconfigure `prometheus` services for the gateway (no
> silent auto-migration). This spec is acceptance-focused and verifiable; it deliberately does not
> prescribe implementation.

## Purpose

Define WHAT must be true of Manage's metric-visualization surface after the `grafana-metric-gateway`
change: metric queries for the `prometheus` service route through a **Grafana gateway**
(`POST {grafana_url}/api/ds/query`) to back a multi-series line **chart**, a scalar **gauge**, and a
windowed **mean**, alongside the instant-query numeric **metric** widget — Prometheus remains the
logical source, Grafana is the transport. In-app charting via `recharts` is the sanctioned renderer;
no `grafana` *service type* (or its widgets/status/UI surfaces) is reintroduced; orphaned Grafana
widget instances degrade gracefully; and operators reconfigure `prometheus` services for the gateway
(no silent auto-migration). This spec is acceptance-focused and verifiable; it deliberately does not
prescribe implementation.

## Requirements

### Requirement: SC-101 — Prometheus range query returns the existing series shape

The `prometheus` service type's config MUST point at a Grafana gateway — declaring `grafana_url` (http(s)-schema-enforced), `datasource_uid` (default `"prometheus"`), and `timeout_seconds` — with a required, Fernet-encrypted `grafana_api_key` secret. The former direct-Prometheus `base_url` config field and the old optional `api_key` secret MUST be gone. When a `prometheus` widget of kind `chart` is fetched, the backend MUST issue `POST {grafana_url}/api/ds/query` (carrying `Authorization: Bearer {grafana_api_key}` and a `queries[0]` entry keyed by `datasource_uid`), MUST NOT issue any direct `GET /api/v1/query_range` against a Prometheus URL, and MUST return a payload of shape `{ "series": [{ "label": str, "points": [{ "t": int, "v": float|null }] }] }` — the exact shape the frontend chart renderer already consumes.

### Requirement: SC-102 — Series label normalization is shared and Prometheus-native

The metric-label → readable-label normalization MUST live in a single shared helper module that holds **both** normalizers — the retained Prom-matrix normalizer (`normalize_prometheus_matrix`) and the (re-)added Grafana-frames normalizer (`normalize_grafana_frames`) — and MUST deduplicate repeated labels via a `label (n)` suffix using **one shared dedup rule** (not duplicated across the two normalizers). Both normalizers produce the same `{label, points}` series shape, and the frames normalizer MUST apply the label fallback chain (displayName → sorted Prometheus labels excluding `__`-prefixed keys → `"value"`).

### Requirement: SC-103 — Range query errors degrade gracefully

A Grafana gateway timeout, connection error, HTTP 401/403 (auth), datasource-not-found, or non-2xx response MUST cause the widget data fetch to return `{ "error": str }` (not raise), so the frontend renders the standard per-widget error state and the rest of the dashboard remains functional. The error message MUST be specific enough to distinguish auth failure from unreachable-host from datasource-not-found where the Grafana response permits.

### Requirement: SC-104 — Step is derived from the window preset

Given a window preset (1h / 6h / 24h / 7d), the backend MUST reuse the existing `WINDOW_PRESETS` and `step_for_window` math to derive the gateway request's `intervalMs` (`step * 1000`), `maxDataPoints`, and `from`/`to` time bounds, landing the resulting point count in the same ~100–300 band as the pre-change direct-Prom path. Users do not configure `from`/`to`/`step`/`intervalMs` directly.

### Requirement: SC-105 — Chart widget moves from grafana to prometheus

Widget kinds `chart`, `gauge`, `mean`, and `metric` MUST remain bound to the `prometheus` service type — the kind strings are persisted in widget instance rows and MUST NOT change. The `grafana` service type MUST NOT be reintroduced and MUST NOT offer any widget kind. The backend adapter (internal class `MetricSource`, registry key still `"prometheus"`) and the frontend `SERVICE_REGISTRY` bind these kinds to the neutral `Metric*` components for `chart`/`gauge`/`mean` (and `PrometheusMetricWidget` for `metric`); all four kinds source their data via the Grafana gateway.

### Requirement: SC-106 — Chart renderer is reused unchanged

The recharts rendering (line chart, multi-series, axes, tooltip, `mergeSeries`, color tokens) MUST be preserved in the rebranded `PrometheusChartWidget`. The rename is structural; the rendering code is not rewritten.

### Requirement: SC-107 — Chart supports multiple series

The `chart` widget MUST render all series returned by the gateway range query, each as its own line with a distinct color (via `normalize_grafana_frames`). There is no single-series restriction on `chart`.

### Requirement: SC-108 — Chart window is a preset

The `chart` widget config MUST expose the time window as a preset selector (`1h`, `6h`, `24h`, `7d`), not raw `from`/`to`/`step` fields. The preset is stored in widget config and resolved to `start`/`end` server-side.

### Requirement: SC-109 — Gauge renders an instant scalar

A widget kind named `gauge` MUST be bound to the `prometheus` service. Its data fetch MUST run an instant PromQL query through the Grafana gateway (a gateway query with a minimal window / single data point) and return the scalar result for rendering as a gauge.

### Requirement: SC-110 — Gauge supports configurable threshold bands

The `gauge` widget config MUST accept optional threshold values (e.g. `warn_at`, `crit_at`) and the renderer MUST display green / amber / red bands accordingly. When thresholds are omitted, the gauge renders with a single neutral color and no bands.

### Requirement: SC-111 — Gauge is scalar-only

The `gauge` widget MUST render exactly one scalar value. If the gateway query returns multiple series, the adapter MUST return `{ "error": str }` (not silently pick one), directing the user to refine the PromQL.

### Requirement: SC-112 — Mean computes client-side over a window

A widget kind named `mean` MUST be bound to the `prometheus` service. Its data fetch MUST run a range query through the Grafana gateway over the configured window preset and return the arithmetic mean of all non-null point values of the single series as a single scalar.

### Requirement: SC-113 — Mean uses plain PromQL + window preset

The `mean` widget config MUST accept a plain PromQL expression (no requirement to wrap in `avg_over_time`) plus a window preset. Users do not write range-vector functions.

### Requirement: SC-114 — Mean is scalar-only

The `mean` widget MUST render exactly one scalar value. If the gateway range query returns multiple series, the adapter MUST return `{ "error": str }` (not silently aggregate across series).

### Requirement: SC-115 — No grafana references in backend source

Grafana is the sanctioned **transport** for the `prometheus` service, so backend source legitimately contains Grafana transport references (e.g. `grafana_url`, `grafana_api_key`, `normalize_grafana_frames`, `POST …/api/ds/query`). After the change, those references are transport-only: there MUST be no `grafana` **service type**, no `grafana` service definition, and no `grafana` entry in the backend `SERVICE_DEFINITIONS` / `SERVICE_ADAPTERS` registries. The `integrations/grafana.py` service-type module stays deleted.

### Requirement: SC-116 — No grafana references in frontend source

Grafana transport is allowed in the frontend — the `prometheus` service config form renders Grafana gateway fields (`grafana_url`, `datasource_uid`) from the backend-provided schema. No frontend code MUST reintroduce a `grafana` **service type**, a Grafana deep-link / dashboard widget, `LinksTab`, or any Grafana-status UI surface. (Test fixtures where "Grafana" appears as a user-authored dashboard *shortcut label* unrelated to a service type remain excluded.)

### Requirement: SC-117 — Grafana service type is gone from registries

Neither the backend `SERVICE_DEFINITIONS` / `SERVICE_ADAPTERS` nor the frontend `SERVICE_REGISTRY` / `BUILTIN_WIDGETS` MUST contain a `grafana` entry. The `integrations/grafana.py` file MUST be deleted.

### Requirement: SC-118 — Grafana status checks and UI sections are removed

The `get_grafana_status` endpoint and its frontend hook (`useGrafanaStatus`) MUST be removed. The UI surface previously in `ObservabilityPage.tsx` has been refactored into a per-service-type `service-tabs/` architecture; the Grafana removal targets are therefore `service-tabs/LinksTab.tsx` + its test, the `grafana` case in `service-tabs/index.ts`, the grafana entry in `integrations/navEntries.ts`, the `grafana` member of `Dashboard.tsx`'s `OBSERVABILITY_TYPES` set, and any Grafana empty-state copy in `ServicesPage.tsx`. The literal `ObservabilityPage.tsx` no longer exists; SC-118's *intent* (no Grafana UI surface) is what is verified.

### Requirement: SC-119 — Grafana widget instances degrade gracefully

An existing persisted widget row referencing a `grafana` service MUST NOT crash the dashboard. It resolves to the existing "unknown widget" error state and surfaces a clear message; the operator can then delete it.

### Requirement: SC-120 — Grafana tests are removed

All Grafana-specific tests (backend and frontend) MUST be deleted; no test references grafana.

### Requirement: SC-121 — config.yaml matches implementation

`openspec/config.yaml` MUST reflect that metric queries for the `prometheus` service are routed through a Grafana gateway (`POST /api/ds/query`) and that in-app charting via `recharts` is the sanctioned renderer. It MUST NOT carry the stale claims "Do NOT re-implement charting in-app", "No recharts/d3 is in use", or "Prometheus is queried directly (no Grafana middleman)".

### Requirement: SC-122 — CHANGELOG documents the migration

`CHANGELOG.md` `[Unreleased]` MUST include a **BREAKING** entry stating that existing `prometheus` service instances must be reconfigured: replace the old `base_url` with `grafana_url`, add the `grafana_api_key` secret, and optionally set `datasource_uid`, because metric queries now route through Grafana's `POST /api/ds/query`.

### Requirement: SC-123 — Backend tests pass

`pytest` run from `backend/` MUST pass, including new tests covering: Prom range query → `{series}` normalization, gauge scalar-only enforcement, mean client-side aggregation, and the shared label helper.

### Requirement: SC-124 — Frontend typechecks, builds, and lints

`npm run build` (which runs `tsc -b` + `vite build`) and `npm run lint` from `frontend/` MUST pass.

### Requirement: SC-125 — New widget kinds have tests

The renamed widgets `MetricChartWidget`, `MetricGaugeWidget`, and `MetricMeanWidget` MUST each have a frontend test covering at least: loading state, error state, and a rendered data case. (The `metric`-kind widget `PrometheusMetricWidget` is not renamed but remains tested.)

### Requirement: SC-126 — No silent data migration

The change MUST NOT auto-migrate persisted `prometheus` service instances from the old `base_url` config shape to the new `grafana_url` gateway shape (URLs and credentials differ; a safe automated rewrite is not possible). Migration is operator-driven per the CHANGELOG note; old-shape instances are flagged on startup (see SC-129) and degrade at runtime to a gateway error until reconfigured.

### Requirement: SC-127 — Non-blocking on the service-storage-harness change

This change MUST NOT depend on the `service-storage-harness` change. It is independently buildable, testable, and deployable. (The reverse dependency holds: the qBit speed widget depends on this change's chart capability.)

### Requirement: SC-128 — get_prometheus_status validates the full gateway path

`get_prometheus_status` MUST validate the full metric path by running a trivial query (e.g. `up`) through the Grafana gateway (`POST {grafana_url}/api/ds/query`). Success MUST return `{ "up": true, "version": <str>, … }` — a sentinel such as `"ok"` is acceptable when Grafana's `/api/ds/query` response carries no Prometheus build-info. Failure MUST return `{ "up": false, "error": <specific str> }` distinguishing auth failure (HTTP 401/403), unreachable host, and datasource/gateway error where the response permits.

### Requirement: SC-129 — Startup logs old-shape prometheus config without crashing

When the backend starts and a persisted `prometheus` service instance carries the old `base_url` config key without `grafana_url`, startup MUST log a clear migration message naming the service and instructing reconfiguration, and MUST complete without crashing (it MUST NOT delete, disable, or otherwise mutate the instance). The instance's widget fetches degrade to a gateway error until the operator reconfigures it.

### Requirement: SC-130 — Grafana is the sanctioned transport for the prometheus service

The `prometheus` service type is the sole metric surface in Manage. Its metric queries (`chart`, `gauge`, `mean`, `metric`) are sanctioned to route through a Grafana gateway — `POST {grafana_url}/api/ds/query` with a `grafana_api_key` and a Prometheus `datasource_uid`. Grafana is the transport, not a first-class service type; a direct-Prometheus HTTP path is not supported.
