@Override
    public Optional<RegionObserver> getRegionObserver() {
      return Optional.of(this);
    }
Thread that does full scans of the table looking for any partially completed rows. Each
iteration of this loads 10 hdfs files, which occupies 5 file open file handles. So every 10
iterations (500 file handles) it does a region compaction to reduce the number of open file
handles.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegionServerBulkLoad.java