TestData: Drop some percentage of CSV values from a request (#70404)

pkg/tsdb/testdatasource/utils.go

@@ -3,6 +3,8 @@ package testdatasource
 import (
 	"math/rand"
 	"time"
+
+	"github.com/grafana/grafana-plugin-sdk-go/data"
 )
 
 type randomStringProvider struct {
@@ -20,3 +22,27 @@ func newRandomStringProvider(data []string) *randomStringProvider {
 func (p *randomStringProvider) Next() string {
 	return p.data[p.r.Int31n(int32(len(p.data)))]
 }
+
+func dropValues(frame *data.Frame, percent float64) (*data.Frame, error) {
+	if frame == nil || percent <= 0 || percent >= 100 {
+		return frame, nil
+	}
+	rows, err := frame.RowLen()
+	copy := frame.EmptyCopy()
+
+	percentage := percent / 100.0
+	seed := time.Now().UnixMilli()
+	r := rand.New(rand.NewSource(seed))
+	for i := 0; i < rows; i++ {
+		if r.Float64() < percentage { // .2 == 20
+			continue
+		}
+
+		// copy the row
+		for fidx, f := range copy.Fields {
+			f.Append(frame.Fields[fidx].At(i))
+		}
+	}
+
+	return copy, err
+}