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

pkg/tsdb/testdatasource/csv_data.go

@@ -39,6 +39,14 @@ func (s *Service) handleCsvContentScenario(ctx context.Context, req *backend.Que
 			return nil, err
 		}
 
+		dropPercent := model.Get("dropPercent").MustFloat64(0)
+		if dropPercent > 0 {
+			frame, err = dropValues(frame, dropPercent)
+			if err != nil {
+				return nil, err
+			}
+		}
+
 		respD := resp.Responses[q.RefID]
 		respD.Frames = append(respD.Frames, frame)
 		resp.Responses[q.RefID] = respD
@@ -68,6 +76,14 @@ func (s *Service) handleCsvFileScenario(ctx context.Context, req *backend.QueryD
 			return nil, err
 		}
 
+		dropPercent := model.Get("dropPercent").MustFloat64(0)
+		if dropPercent > 0 {
+			frame, err = dropValues(frame, dropPercent)
+			if err != nil {
+				return nil, err
+			}
+		}
+
 		respD := resp.Responses[q.RefID]
 		respD.Frames = append(respD.Frames, frame)
 		resp.Responses[q.RefID] = respD

pkg/tsdb/testdatasource/kinds/dataquery/types_dataquery_gen.go

@@ -154,11 +154,14 @@ type TestDataDataQuery struct {
 	// Specific implementations will *extend* this interface, adding the required
 	// properties for the given context.
 	DataQuery
-	Alias           *string            `json:"alias,omitempty"`
-	Channel         *string            `json:"channel,omitempty"`
-	CsvContent      *string            `json:"csvContent,omitempty"`
-	CsvFileName     *string            `json:"csvFileName,omitempty"`
-	CsvWave         []CSVWave          `json:"csvWave,omitempty"`
+	Alias       *string   `json:"alias,omitempty"`
+	Channel     *string   `json:"channel,omitempty"`
+	CsvContent  *string   `json:"csvContent,omitempty"`
+	CsvFileName *string   `json:"csvFileName,omitempty"`
+	CsvWave     []CSVWave `json:"csvWave,omitempty"`
+
+	// Drop percentage (the chance we will lose a point 0-100)
+	DropPercent     *float64           `json:"dropPercent,omitempty"`
 	ErrorType       *ErrorType         `json:"errorType,omitempty"`
 	Labels          *string            `json:"labels,omitempty"`
 	LevelColumn     *bool              `json:"levelColumn,omitempty"`

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
+}