public boolean verify() {
      try {
        Counters counters = job.getCounters();
        if (counters == null) {
          LOG.info("Counters object was null, Generator verification cannot be performed."
            + " This is commonly a result of insufficient YARN configuration.");
          return false;
        }

        if (
          counters.findCounter(GeneratorCounts.TERMINATING).getValue() > 0
            || counters.findCounter(GeneratorCounts.UNDEFINED).getValue() > 0
            || counters.findCounter(GeneratorCounts.IOEXCEPTION).getValue() > 0
        ) {
          LOG.error("Concurrent walker failed to verify during Generation phase");
          LOG.error(
            "TERMINATING nodes: " + counters.findCounter(GeneratorCounts.TERMINATING).getValue());
          LOG.error(
            "UNDEFINED nodes: " + counters.findCounter(GeneratorCounts.UNDEFINED).getValue());
          LOG.error(
            "IOEXCEPTION nodes: " + counters.findCounter(GeneratorCounts.IOEXCEPTION).getValue());
          return false;
        }
      } catch (IOException e) {
        LOG.info("Generator verification could not find counter");
        return false;
      }
      return true;
    }
Randomly selects and walks a random flushed loop concurrently with the Generator Mapper by
spawning ConcurrentWalker's with specified StartNodes. These ConcurrentWalker's are
configured to only log erroneous nodes.
hbase-it/src/test/java/org/apache/hadoop/hbase/test/IntegrationTestBigLinkedList.java