perf: Restperf should stream results while parsing

cmd/collectors/restperf/restperf.go

@@ -761,7 +761,7 @@ func (r *RestPerf) PollData() (map[string]*matrix.Matrix, error) {
 
 	processBatch := func(perfRecords []rest.PerfRecord) error {
 		if len(perfRecords) == 0 {
-			return errs.New(errs.ErrNoInstance, "no "+r.Object+" instances on cluster")
+			return nil
 		}
 
 		// Process the current batch of records

cmd/tools/rest/rest.go

@@ -473,7 +473,7 @@ func FetchAnalytics(client *Client, href string) ([]gjson.Result, gjson.Result,
 func FetchRestPerfDataStream(client *Client, href string, processBatch func([]PerfRecord) error, headers ...map[string]string) error {
 	var prevLink string
 	nextLink := href
-
+	recordsFound := false
 	for {
 		response, err := client.GetRest(nextLink, headers...)
 		if err != nil {
@@ -487,15 +487,11 @@ func FetchRestPerfDataStream(client *Client, href string, processBatch func([]Pe
 		next := output.Get("_links.next.href")
 
 		if numRecords.Int() > 0 {
+			recordsFound = true
 			p := PerfRecord{Records: data, Timestamp: time.Now().UnixNano()}
 			if err := processBatch([]PerfRecord{p}); err != nil {
 				return err
 			}
-		} else {
-			// Call processBatch with an empty list to handle no records scenario
-			if err := processBatch([]PerfRecord{}); err != nil {
-				return err
-			}
 		}
 
 		prevLink = nextLink
@@ -506,6 +502,9 @@ func FetchRestPerfDataStream(client *Client, href string, processBatch func([]Pe
 			break
 		}
 	}
+	if !recordsFound {
+		return errs.New(errs.ErrNoInstance, "no instances found")
+	}
 
 	return nil
 }