private void isSuccessfulScan(RegionInfo region) throws IOException {
    Scan scan = new Scan().withStartRow(region.getStartKey()).withStopRow(region.getEndKey(), false)
      .setRaw(true).setOneRowLimit().setMaxResultSize(1L).setCaching(1)
      .setFilter(new FirstKeyOnlyFilter()).setCacheBlocks(false);
    try (Table table = conn.getTable(region.getTable());
      ResultScanner scanner = table.getScanner(scan)) {
      scanner.next();
    } catch (IOException e) {
      LOG.error("Could not scan region: {}", region.getEncodedName(), e);
      throw e;
    }
  }
Tries to scan a row from passed region
hbase-server/src/main/java/org/apache/hadoop/hbase/util/MoveWithAck.java