private void computeMaxFailures() {
    maxFailures = 0;
    for (Integer failCount : failures.values()) {
      if (maxFailures < failCount.intValue()) {
        maxFailures = failCount.intValue();
      }
    }
  }
JobDebugger takes a RunningJob that has failed and grabs the top 4 failing
tasks and outputs this information to the Hive CLI.
ql/src/java/org/apache/hadoop/hive/ql/exec/mr/JobDebugger.java