IG-16745: grafana: in case query request is empty ignore it and return empty array (#582) (#583)

Co-authored-by: Katya Katsenelenbogen <katyak@iguazio.com>

Author: dinal

http/grafana.go

@@ -37,7 +37,6 @@ import (
 
 const querySeparator = ";"
 const fieldsItemsSeperator = ","
-const defaultBackend = "tsdb"
 
 type outputType int
 
@@ -108,14 +107,15 @@ func simpleJSONRequestFactory(method string, request []byte) ([]simpleJSONReques
 	switch method {
 	case "query":
 		for _, target := range reqBase.Targets {
-			currRequest := &simpleJSONQueryRequest{Backend: defaultBackend, requestSimpleJSONBase: reqBase}
+			currRequest := &simpleJSONQueryRequest{requestSimpleJSONBase: reqBase}
 			currRequest.Type = target["type"].(string)
 			fieldInput := target["target"].(string)
 			if err := currRequest.parseQueryLine(fieldInput); err != nil {
 				return nil, errors.Wrap(err, "Failed to parse target")
 			}
-
-			requests = append(requests, currRequest)
+			if currRequest.Backend != "" {
+				requests = append(requests, currRequest)
+			}
 		}
 	case "search":
 		currRequest :=

http/server.go

@@ -470,18 +470,20 @@ func (s *Server) handleSimpleJSON(ctx *fasthttp.RequestCtx, method string) {
 		ctx.Error(fmt.Sprintf("bad request - %s", err), http.StatusBadRequest)
 		return
 	}
-
 	var results interface{}
-	for _, req := range requests {
-		result, err := s.executeSimpleJSONSubRequest(req, ctx)
-		if err != nil {
-			ctx.Error(fmt.Sprintf("Error querying: %s", err.Error()), http.StatusInternalServerError)
-			return
+	if len(requests) > 0 {
+		for _, req := range requests {
+			result, err := s.executeSimpleJSONSubRequest(req, ctx)
+			if err != nil {
+				ctx.Error(fmt.Sprintf("Error querying: %s", err.Error()), http.StatusInternalServerError)
+				return
+			}
+			results = appendSimpleJSONResults(results, result)
 		}
-
-		results = appendSimpleJSONResults(results, result)
+	} else {
+		a := make([]string, 0)
+		results = a
 	}
-
 	_ = s.replyJSON(ctx, results)
 }