Alerting: Extract values from MD expr alerts (#34757)

When using mulit-dimensional Grafana managed alerts (e.g. SSE math) extract refIds values and labels so they can be shown in the notification and dashboards.

pkg/services/ngalert/eval/extract_md.go

@@ -17,30 +17,51 @@ func extractEvalString(frame *data.Frame) (s string) {
 		return
 	}
 
-	evalMatches, ok := frame.Meta.Custom.([]classic.EvalMatch)
-	if !ok {
-		return
+	if evalMatches, ok := frame.Meta.Custom.([]classic.EvalMatch); ok {
+		sb := strings.Builder{}
+
+		for i, m := range evalMatches {
+			sb.WriteString("[ ")
+			sb.WriteString(fmt.Sprintf("metric='%s' ", m.Metric))
+			sb.WriteString(fmt.Sprintf("labels={%s} ", m.Labels))
+
+			valString := "null"
+			if m.Value != nil {
+				valString = fmt.Sprintf("%v", *m.Value)
+			}
+
+			sb.WriteString(fmt.Sprintf("value=%v ", valString))
+
+			sb.WriteString("]")
+			if i < len(evalMatches)-1 {
+				sb.WriteString(", ")
+			}
+		}
+		return sb.String()
 	}
 
-	sb := strings.Builder{}
+	if caps, ok := frame.Meta.Custom.([]NumberValueCapture); ok {
+		sb := strings.Builder{}
 
-	for i, m := range evalMatches {
-		sb.WriteString("[ ")
-		sb.WriteString(fmt.Sprintf("metric='%s' ", m.Metric))
-		sb.WriteString(fmt.Sprintf("labels={%s} ", m.Labels))
+		for i, c := range caps {
+			sb.WriteString("[ ")
+			sb.WriteString(fmt.Sprintf("var='%s' ", c.Var))
+			sb.WriteString(fmt.Sprintf("labels={%s} ", c.Labels))
 
-		valString := "null"
-		if m.Value != nil {
-			valString = fmt.Sprintf("%v", *m.Value)
-		}
+			valString := "null"
+			if c.Value != nil {
+				valString = fmt.Sprintf("%v", *c.Value)
+			}
 
-		sb.WriteString(fmt.Sprintf("value=%v ", valString))
+			sb.WriteString(fmt.Sprintf("value=%v ", valString))
 
-		sb.WriteString("]")
-		if i < len(evalMatches)-1 {
-			sb.WriteString(", ")
+			sb.WriteString("]")
+			if i < len(caps)-1 {
+				sb.WriteString(", ")
+			}
 		}
+		return sb.String()
 	}
 
-	return sb.String()
+	return ""
 }