private void updateDeleteTombstoneStats(StoreStats storeStats) {
    DeleteTombstoneStats currentDeleteStats = aggregatedDeleteTombstoneStats.get();
    DeleteTombstoneStats anotherDeleteStats = storeStats.getDeleteTombstoneStats();
    DeleteTombstoneStats newDeleteStats = currentDeleteStats.merge(anotherDeleteStats);
    aggregatedDeleteTombstoneStats.set(newDeleteStats);
  }
Update delete tombstone related stats from given {@link StoreStats}
@param storeStats the {@link StoreStats} that contains delete tombstone stats of single store.
ambry-server/src/main/java/com/github/ambry/server/StatsManager.java