protected void handleFailure(Counters counters) throws IOException {
      Configuration conf = job.getConfiguration();
      TableName tableName = getTableName(conf);
      try (Connection conn = ConnectionFactory.createConnection(conf)) {
        try (RegionLocator rl = conn.getRegionLocator(tableName)) {
          CounterGroup g = counters.getGroup("undef");
          Iterator<Counter> it = g.iterator();
          while (it.hasNext()) {
            String keyString = it.next().getName();
            byte[] key = Bytes.toBytes(keyString);
            HRegionLocation loc = rl.getRegionLocation(key, true);
            LOG.error("undefined row " + keyString + ", " + loc);
          }
          g = counters.getGroup("unref");
          it = g.iterator();
          while (it.hasNext()) {
            String keyString = it.next().getName();
            byte[] key = Bytes.toBytes(keyString);
            HRegionLocation loc = rl.getRegionLocation(key, true);
            LOG.error("unreferred row " + keyString + ", " + loc);
          }
        }
      }
    }
Verify that the Counters don't contain values which indicate an outright failure from the
Reducers. The Job's counters
@return True if the "bad" counter objects are 0, false otherwise
hbase-it/src/test/java/org/apache/hadoop/hbase/test/IntegrationTestBigLinkedList.java