Add SerializeBatch method to the Serializer interface (#4107)

plugins/serializers/influx/influx.go

@@ -102,6 +102,17 @@ func (s *Serializer) Serialize(m telegraf.Metric) ([]byte, error) {
 	return out, nil
 }
 
+func (s *Serializer) SerializeBatch(metrics []telegraf.Metric) ([]byte, error) {
+	var batch bytes.Buffer
+	for _, m := range metrics {
+		_, err := s.Write(&batch, m)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return batch.Bytes(), nil
+}
+
 func (s *Serializer) Write(w io.Writer, m telegraf.Metric) (int, error) {
 	err := s.writeMetric(w, m)
 	return s.bytesWritten, err

plugins/serializers/influx/influx_test.go

@@ -447,3 +447,24 @@ func BenchmarkSerializer(b *testing.B) {
 		})
 	}
 }
+
+func TestSerialize_SerializeBatch(t *testing.T) {
+	m := MustMetric(
+		metric.New(
+			"cpu",
+			map[string]string{},
+			map[string]interface{}{
+				"value": 42.0,
+			},
+			time.Unix(0, 0),
+		),
+	)
+
+	metrics := []telegraf.Metric{m, m}
+
+	serializer := NewSerializer()
+	serializer.SetFieldSortOrder(SortFields)
+	output, err := serializer.SerializeBatch(metrics)
+	require.NoError(t, err)
+	require.Equal(t, []byte("cpu value=42 0\ncpu value=42 0\n"), output)
+}