code: func (s *session) flushManifest(rec *sessionRecord) (err error) {
  	s.fillRecord(rec, false)
  	w, err := s.manifest.Next()
  	if err != nil {
  		return
  	}
  	err = rec.encode(w)
  	if err != nil {
  		return
  	}
  	err = s.manifest.Flush()
  	if err != nil {
  		return
  	}
  	if !s.o.GetNoSync() {
  		err = s.manifestWriter.Sync()
  		if err != nil {
  			return
  		}
  	}
  	s.recordCommited(rec)
  	return
  }
docs: // Flush record to disk.