code: public VoltTable getStatsAggregate(
              final StatsSelector selector,
              final boolean interval,
              final Long now) {
          return getStatsAggregateInternal(selector, interval, now);
      }
docs: Get aggregate statistics on this node for the given selector.
  If you need both site-wise and node-wise stats, register the appropriate StatsSources for that
  selector with each siteId and then some other value for the node-level stats (PLANNER stats uses -1).
  This call will automatically aggregate every StatsSource registered for every 'site'ID for that selector.
  
  @param selector    @Statistics selector keyword
  @param interval    true if processing a reporting interval
  @param now         current timestamp
  @return  statistics VoltTable results