Configure Prometheus function dialog shows wrong presets for native histograms

Summary

The "Configure the Prometheus function" drawer determines which presets to show (Heatmap, Percentiles, Sum, Avg, etc.) by re-deriving the metric type from Prometheus /metadata. Prometheus metadata is unreliable for native histograms — it frequently returns no entry or a non-histogram type — so the drawer falls back to the gauge preset list and the Heatmap option never appears for those metrics. This is the same root cause that PR #1207 fixed for the main viz panel by switching to data-frame–based detection. That fix did not extend to the configure drawer, so the drawer is still metadata-only.

Repro

1. Open Metrics Drilldown for a native-histogram metric whose Prometheus /metadata does not return type: histogram. Example we hit this on: adaptive_logs_get_exemptions_success_latency_seconds.
2. Wait for the main panel to render. With #1207, the main panel correctly identifies it as a native histogram via the data frame and renders as a heatmap.
3. Click the "Configure Prometheus function" cog in the panel header.
4. Expected: the drawer shows the histogram presets (Heatmap (default), Percentiles).
5. Actual: the drawer shows the gauge presets (Average, Sum, Standard deviation, Percentiles, Minimum and maximum). The drawer subtitle reads <metric> (gauge). For comparison, classic histograms (e.g. adaptive_logs_api_request_duration_seconds_bucket) work correctly because they are detected synchronously from the _bucket suffix.

Root cause

ConfigurePanelForm.buildBody passes only metric.name and re-derives the type:

// src/shared/GmdVizPanel/components/ConfigurePanelForm/ConfigurePanelForm.tsx
const presets = await getConfigPresetsForMetric(metric.name, getTrailFor(this));

getConfigPresetsForMetric then asks getMetricType, which is metadata-only:

// src/shared/GmdVizPanel/config/presets/getConfigPresetsForMetric.ts
export async function getConfigPresetsForMetric(metric: string, dataTrail: DataTrail): Promise<PanelConfigPreset[]> {
  const metricType = await getMetricType(metric, dataTrail);
  switch (metricType) {
    case 'classic-histogram':
    case 'native-histogram':
      return Object.values(DEFAULT_HISTOGRAMS_PRESETS);
    ...
    default:
      return Object.values(DEFAULT_TIMESERIES_PRESETS);
  }
}

// src/shared/GmdVizPanel/matchers/getMetricType.ts
if (metricType === 'gauge') {
  const metadata = await dataTrail.getMetadataForMetric(metric);
  if (metadata?.type === 'histogram') {
    return 'native-histogram';
  }
  ...
}

So when metadata doesn't say histogram, the drawer falls into the default (timeseries/gauge) branch regardless of what the data frames actually look like. By the time the user clicks the cog, the surrounding MetricGraphScene has already updated ConfigurePanelAction's metric.type to 'native-histogram' (via the data-frame subscription in GmdVizPanel), but the dialog ignores that resolved type and re-asks metadata.

Why PR #1207 alone is not enough

#1207 moved the main panel off of metadata for native-histogram detection, which is correct. But the configure drawer still relies on metadata via getConfigPresetsForMetric → getMetricType. So the drawer remains broken on exactly the metrics #1207 was motivated by.

Proposed fixes (pick one)

Option 1 — Trust the resolved Metric.type (smaller change)

Change getConfigPresetsForMetric to take the already-resolved metric type instead of re-deriving it, and have ConfigurePanelForm pass it through:

// getConfigPresetsForMetric.ts — sketch
export function getConfigPresetsForMetric(metricType: MetricType): PanelConfigPreset[] {
  switch (metricType) { ... }
}
// ConfigurePanelForm.tsx — sketch
const presets = getConfigPresetsForMetric(metric.type);

By the time the cog is clickable and clicked, metric.type is the value that MetricGraphScene already corrected from data frames. This is consistent with the direction of #1207.

Caveat: if the user clicks the cog before the main panel's first query completes, metric.type will still be the synchronous heuristic ('gauge') and the drawer will show gauge presets. We may want to disable or delay the cog until the main panel has resolved its type, or fall back to Option 2 for robustness.

Option 2 — Drawer-side data-frame probe (more robust)

Have ConfigurePanelForm subscribe to the same data-frame signal GmdVizPanel uses, and rebuild its preset list when HeatmapCells is seen. This removes any dependency on click timing or MetricGraphScene having already corrected the type, but is a larger change.

Acceptance criteria

• For a native histogram with broken/missing Prometheus metadata, the configure drawer shows the histogram presets (Heatmap default + Percentiles).
• The drawer subtitle reads <metric> (native-histogram).
• Behavior unchanged for classic histograms, gauges, counters, etc.
• Tests cover the case where getMetricType would return 'gauge' but the metric is actually a native histogram (i.e., metadata disagrees with reality).

Related

• PR #1207 — fix(native-histogram): rely solely on data frames for native histogram detection (covers the main viz panel only)