private int updateAttrCache() {
   LOG.debug("Updating attr cache...");
   int recNo = 0;
   int numMetrics = 0;
   for (MetricsRecordImpl record : lastRecs) {
     for (MetricsTag t : record.tags()) {
       setAttrCacheTag(t, recNo);
       ++numMetrics;
     }
     for (Metric m : record.metrics()) {
       setAttrCacheMetric(m, recNo);
       ++numMetrics;
     }
     ++recNo;
   }
   LOG.debug("Done. numMetrics=" + numMetrics);
   return numMetrics;
 }