code: func (r Req) TraceLog(span opentracing.Span) {
  	span.LogFields(
  		log.Object("key", r.MKey),
  		log.String("target", r.Target),
  		log.String("pattern", r.Pattern),
  		log.Int("from", int(r.From)),
  		log.Int("to", int(r.To)),
  		log.Int("span", int(r.To-r.From-1)),
  		log.Int("mdp", int(r.MaxPoints)),
  		log.Int("rawInterval", int(r.RawInterval)),
  		log.String("cons", r.Consolidator.String()),
  		log.String("consReq", r.ConsReq.String()),
  		log.Int("schemaId", int(r.SchemaId)),
  		log.Int("aggId", int(r.AggId)),
  		log.Int("archive", r.Archive),
  		log.Int("archInterval", int(r.ArchInterval)),
  		log.Int("TTL", int(r.TTL)),
  		log.Int("outInterval", int(r.OutInterval)),
  		log.Int("aggNum", int(r.AggNum)),
  	)
  }
docs: // TraceLog puts all request properties in a span log entry
  // good for when a span deals with multiple requests
  // note that the amount of data generated here can be up to
  // 1000~1500 bytes