Add an incremental reporter that prints the latency

lib/reporters.go

@@ -106,6 +106,19 @@ var ReportText ReporterFunc = func(r Results) ([]byte, error) {
 	return out.Bytes(), nil
 }
 
+var ReportIncrementalLatency ReporterFunc = func(r Results) ([]byte, error) {
+	m := NewMetrics(r)
+	out := &bytes.Buffer{}
+
+	w := tabwriter.NewWriter(out, 0, 8, 2, '\t', tabwriter.StripEscape)
+	fmt.Fprintf(w, "%s\n", strings.TrimSuffix(m.Latencies.Mean.String(), "ms"))
+
+	if err := w.Flush(); err != nil {
+		return []byte{}, err
+	}
+	return out.Bytes(), nil
+}
+
 // ReportJSON writes a computed Metrics struct to as JSON
 var ReportJSON ReporterFunc = func(r Results) ([]byte, error) {
 	return json.Marshal(NewMetrics(r))

report.go

@@ -14,7 +14,7 @@ import (
 
 func reportCmd() command {
 	fs := flag.NewFlagSet("vegeta report", flag.ExitOnError)
-	reporter := fs.String("reporter", "text", "Reporter [text, json, plot, hist[buckets]]")
+	reporter := fs.String("reporter", "text", "Reporter [text, json, plot, hist[buckets], incrementalLatency]")
 	inputs := fs.String("inputs", "stdin", "Input files (comma separated)")
 	output := fs.String("output", "stdout", "Output file")
 	return command{fs, func(args []string) error {
@@ -30,6 +30,7 @@ func report(reporter, inputs, output string) error {
 		return fmt.Errorf("bad reporter: %s", reporter)
 	}
 	var rep vegeta.Reporter
+	var incremental = false
 	switch reporter[:4] {
 	case "text":
 		rep = vegeta.ReportText
@@ -46,6 +47,9 @@ func report(reporter, inputs, output string) error {
 			return err
 		}
 		rep = hist
+	case "incr":
+		incremental = true
+		rep = vegeta.ReportIncrementalLatency
 	}
 
 	files := strings.Split(inputs, ",")
@@ -80,6 +84,17 @@ outer:
 				break outer
 			}
 			results = append(results, r)
+			if incremental == true {
+				data, err := rep.Report(results)
+				if err != nil {
+					return err
+				}
+				_, err = out.Write(data)
+				if err != nil {
+					return err
+				}
+				results = results[:0]
+			}
 		case err, ok := <-errs:
 			if !ok {
 				break outer
@@ -88,11 +103,14 @@ outer:
 		}
 	}
 
-	sort.Sort(results)
-	data, err := rep.Report(results)
-	if err != nil {
+	if incremental == false {
+		sort.Sort(results)
+		data, err := rep.Report(results)
+		if err != nil {
+			return err
+		}
+		_, err = out.Write(data)
 		return err
 	}
-	_, err = out.Write(data)
-	return err
+	return nil
 }