@Override
    protected void initializeKVHeap(List<KeyValueScanner> scanners,
      List<KeyValueScanner> joinedScanners, HRegion region) throws IOException {
      this.storeHeap =
        new HeartbeatReversedKVHeap(scanners, (CellComparatorImpl) region.getCellComparator());
      if (!joinedScanners.isEmpty()) {
        this.joinedHeap = new HeartbeatReversedKVHeap(joinedScanners,
          (CellComparatorImpl) region.getCellComparator());
      }
    }
Custom ReversedRegionScanner that can be configured to sleep between retrievals of row Results
and/or column family cells
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestScannerHeartbeatMessages.java