Loki: alerting: handle variables like __interval and __range (#42126)

pkg/tsdb/loki/parse_query.go

@@ -0,0 +1,75 @@
+package loki
+
+import (
+	"encoding/json"
+	"math"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/grafana/grafana/pkg/tsdb/intervalv2"
+)
+
+const (
+	varInterval   = "$__interval"
+	varIntervalMs = "$__interval_ms"
+	varRange      = "$__range"
+	varRangeS     = "$__range_s"
+	varRangeMs    = "$__range_ms"
+)
+
+func interpolateVariables(expr string, interval time.Duration, timeRange time.Duration) string {
+	intervalText := intervalv2.FormatDuration(interval)
+	intervalMsText := strconv.FormatInt(int64(interval/time.Millisecond), 10)
+
+	rangeMs := timeRange.Milliseconds()
+	rangeSRounded := int64(math.Round(float64(rangeMs) / 1000.0))
+	rangeMsText := strconv.FormatInt(rangeMs, 10)
+	rangeSText := strconv.FormatInt(rangeSRounded, 10)
+
+	expr = strings.ReplaceAll(expr, varIntervalMs, intervalMsText)
+	expr = strings.ReplaceAll(expr, varInterval, intervalText)
+	expr = strings.ReplaceAll(expr, varRangeMs, rangeMsText)
+	expr = strings.ReplaceAll(expr, varRangeS, rangeSText)
+	expr = strings.ReplaceAll(expr, varRange, rangeSText+"s")
+
+	return expr
+}
+
+func parseQuery(dsInfo *datasourceInfo, queryContext *backend.QueryDataRequest) ([]*lokiQuery, error) {
+	qs := []*lokiQuery{}
+	for _, query := range queryContext.Queries {
+		model := &ResponseModel{}
+		err := json.Unmarshal(query.JSON, model)
+		if err != nil {
+			return nil, err
+		}
+
+		start := query.TimeRange.From
+		end := query.TimeRange.To
+
+		var resolution int64 = 1
+		if model.Resolution >= 1 && model.Resolution <= 5 || model.Resolution == 10 {
+			resolution = model.Resolution
+		}
+
+		interval := query.Interval
+		timeRange := query.TimeRange.To.Sub(query.TimeRange.From)
+
+		step := calculateStep(interval, timeRange, resolution)
+
+		expr := interpolateVariables(model.Expr, interval, timeRange)
+
+		qs = append(qs, &lokiQuery{
+			Expr:         expr,
+			Step:         step,
+			LegendFormat: model.LegendFormat,
+			Start:        start,
+			End:          end,
+			RefID:        query.RefID,
+		})
+	}
+
+	return qs, nil
+}