src/server/worker/api_server.go
func mergeStats(x, y *pps.ProcessStats) error {
	var err error
	if x.DownloadTime, err = plusDuration(x.DownloadTime, y.DownloadTime); err != nil {
		return err
	}
	if x.ProcessTime, err = plusDuration(x.ProcessTime, y.ProcessTime); err != nil {
		return err
	}
	if x.UploadTime, err = plusDuration(x.UploadTime, y.UploadTime); err != nil {
		return err
	}
	x.DownloadBytes += y.DownloadBytes
	x.UploadBytes += y.UploadBytes
	return nil
}
func mergeStats(x, y *pps.ProcessStats) error {
	var err error
	if x.DownloadTime, err = plusDuration(x.DownloadTime, y.DownloadTime); err != nil {
		return err
	}
	if x.ProcessTime, err = plusDuration(x.ProcessTime, y.ProcessTime); err != nil {
		return err
	}
	if x.UploadTime, err = plusDuration(x.UploadTime, y.UploadTime); err != nil {
		return err
	}
	x.DownloadBytes += y.DownloadBytes
	x.UploadBytes += y.UploadBytes
	return nil
}
// mergeStats merges y into x