code: func (a *AggMetric) addAggregators(ts uint32, val float64) {
  	for _, agg := range a.aggregators {
  		log.Debugf("AM: %s pushing %d,%f to aggregator %d", a.key, ts, val, agg.span)
  		agg.Add(ts, val)
  	}
  }
docs: // caller must hold lock