@SuppressWarnings("JavaUtilDate")
      private StringBuilder dumpExtraInfoOnRefs(final BytesWritable key, final Context context,
        final List<byte[]> refs) throws IOException {
        StringBuilder refsSb = null;
        if (refs.isEmpty()) return refsSb;
        refsSb = new StringBuilder();
        String comma = "";
        // If a row is a reference but has no define, print the content of the row that has
        // this row as a 'prev'; it will help debug. The missing row was written just before
        // the row we are dumping out here.
        TableName tn = getTableName(context.getConfiguration());
        try (Table t = this.connection.getTable(tn)) {
          for (byte[] ref : refs) {
            Result r = t.get(new Get(ref));
            List<Cell> cells = r.listCells();
            String ts = (cells != null && !cells.isEmpty())
              ? new java.util.Date(cells.get(0).getTimestamp()).toString()
              : "";
            byte[] b = r.getValue(FAMILY_NAME, COLUMN_CLIENT);
            String jobStr = (b != null && b.length > 0) ? Bytes.toString(b) : "";
            b = r.getValue(FAMILY_NAME, COLUMN_COUNT);
            long count = (b != null && b.length > 0) ? Bytes.toLong(b) : -1;
            b = r.getValue(FAMILY_NAME, COLUMN_PREV);
            String refRegionLocation = "";
            String keyRegionLocation = "";
            if (b != null && b.length > 0) {
              try (RegionLocator rl = this.connection.getRegionLocator(tn)) {
                HRegionLocation hrl = rl.getRegionLocation(b);
                if (hrl != null) refRegionLocation = hrl.toString();
                // Key here probably has trailing zeros on it.
                hrl = rl.getRegionLocation(key.getBytes());
                if (hrl != null) keyRegionLocation = hrl.toString();
              }
            }
            LOG.error("Extras on ref without a def, ref=" + Bytes.toStringBinary(ref)
              + ", refPrevEqualsKey="
              + (Bytes.compareTo(key.getBytes(), 0, key.getLength(), b, 0, b.length) == 0)
              + ", key=" + Bytes.toStringBinary(key.getBytes(), 0, key.getLength())
              + ", ref row date=" + ts + ", jobStr=" + jobStr + ", ref row count=" + count
              + ", ref row regionLocation=" + refRegionLocation + ", key row regionLocation="
              + keyRegionLocation);
            refsSb.append(comma);
            comma = ",";
            refsSb.append(Bytes.toStringBinary(ref));
          }
        }
        return refsSb;
      }
Dump out extra info around references if there are any. Helps debugging.
@return StringBuilder filled with references if any.
hbase-it/src/test/java/org/apache/hadoop/hbase/test/IntegrationTestBigLinkedList.java