Loki: add backend-forward mode to queries, update log-row-context (#47726)

* loki: add helper function to sort dataframe by time

* loki: add direction-attribute to queries

* loki: make log-row-context code backward-compatible

* better comment

Co-authored-by: Ivana Huckova <30407135+ivanahuckova@users.noreply.github.com>

* fixed test

* simplified code

Co-authored-by: Ivana Huckova <30407135+ivanahuckova@users.noreply.github.com>

pkg/tsdb/loki/api.go

@@ -29,6 +29,8 @@ func makeRequest(ctx context.Context, lokiDsUrl string, query lokiQuery) (*http.
 	qs := url.Values{}
 	qs.Set("query", query.Expr)
 
+	qs.Set("direction", string(query.Direction))
+
 	// MaxLines defaults to zero when not received,
 	// and Loki does not like limit=0, even when it is not needed
 	// (for example for metric queries), so we

pkg/tsdb/loki/framing_test.go

@@ -22,9 +22,9 @@ import (
 // but i wanted to test for all of them, to be sure.
 
 func TestSuccessResponse(t *testing.T) {
-	matrixQuery := lokiQuery{Expr: "up(ALERTS)", Step: time.Second * 42, QueryType: QueryTypeRange}
-	vectorQuery := lokiQuery{Expr: "query1", QueryType: QueryTypeInstant}
-	streamsQuery := lokiQuery{Expr: "query1", QueryType: QueryTypeRange}
+	matrixQuery := lokiQuery{Expr: "up(ALERTS)", Step: time.Second * 42, QueryType: QueryTypeRange, Direction: DirectionBackward}
+	vectorQuery := lokiQuery{Expr: "query1", QueryType: QueryTypeInstant, Direction: DirectionBackward}
+	streamsQuery := lokiQuery{Expr: "query1", QueryType: QueryTypeRange, Direction: DirectionBackward}
 
 	tt := []struct {
 		name     string
@@ -119,7 +119,7 @@ func TestErrorResponse(t *testing.T) {
 
 	for _, test := range tt {
 		t.Run(test.name, func(t *testing.T) {
-			frames, err := runQuery(context.Background(), makeMockedAPI(400, test.contentType, test.body), &lokiQuery{QueryType: QueryTypeRange})
+			frames, err := runQuery(context.Background(), makeMockedAPI(400, test.contentType, test.body), &lokiQuery{QueryType: QueryTypeRange, Direction: DirectionBackward})
 
 			require.Len(t, frames, 0)
 			require.Error(t, err)

pkg/tsdb/loki/loki.go

@@ -53,6 +53,7 @@ type datasourceInfo struct {
 type QueryJSONModel struct {
 	QueryType    string `json:"queryType"`
 	Expr         string `json:"expr"`
+	Direction    string `json:"direction"`
 	LegendFormat string `json:"legendFormat"`
 	Interval     string `json:"interval"`
 	IntervalMS   int    `json:"intervalMS"`

pkg/tsdb/loki/parse_query.go

@@ -67,6 +67,21 @@ func parseQueryType(jsonValue string) (QueryType, error) {
 	}
 }
 
+func parseDirection(jsonValue string) (Direction, error) {
+	switch jsonValue {
+	case "backward":
+		return DirectionBackward, nil
+	case "forward":
+		return DirectionForward, nil
+	case "":
+		// there are older queries stored in alerting that did not have queryDirection,
+		// we default to "backward"
+		return DirectionBackward, nil
+	default:
+		return DirectionBackward, fmt.Errorf("invalid queryDirection: %s", jsonValue)
+	}
+}
+
 func parseQuery(queryContext *backend.QueryDataRequest) ([]*lokiQuery, error) {
 	qs := []*lokiQuery{}
 	for _, query := range queryContext.Queries {
@@ -95,9 +110,15 @@ func parseQuery(queryContext *backend.QueryDataRequest) ([]*lokiQuery, error) {
 			return nil, err
 		}
 
+		direction, err := parseDirection(model.Direction)
+		if err != nil {
+			return nil, err
+		}
+
 		qs = append(qs, &lokiQuery{
 			Expr:         expr,
 			QueryType:    queryType,
+			Direction:    direction,
 			Step:         step,
 			MaxLines:     model.MaxLines,
 			LegendFormat: model.LegendFormat,

pkg/tsdb/loki/types.go

@@ -9,9 +9,17 @@ const (
 	QueryTypeInstant QueryType = "instant"
 )
 
+type Direction string
+
+const (
+	DirectionBackward Direction = "backward"
+	DirectionForward  Direction = "forward"
+)
+
 type lokiQuery struct {
 	Expr         string
 	QueryType    QueryType
+	Direction    Direction
 	Step         time.Duration
 	MaxLines     int
 	LegendFormat string