private String showJobFailDebugInfo() throws IOException {
    console.printError("Error during job, obtaining debugging information...");
    if (!conf.get("mapred.job.tracker", "local").equals("local")) {
      // Show Tracking URL for remotely running jobs.
      console.printError("Job Tracking URL: " + rj.getTrackingURL());
    }
    // Loop to get all task completion events because getTaskCompletionEvents
    // only returns a subset per call
    TaskInfoGrabber tlg = new TaskInfoGrabber();
    Thread t = new Thread(tlg);
    try {
      t.start();
      t.join(HiveConf.getIntVar(conf, HiveConf.ConfVars.TASKLOG_DEBUG_TIMEOUT));
    } catch (InterruptedException e) {
      console.printError("Timed out trying to finish grabbing task log URLs, "
          + "some task info may be missing");
    }

    // Remove failures for tasks that succeeded
    for (String task : successes) {
      failures.remove(task);
    }

    if (failures.keySet().size() == 0) {
      return null;
    }
    // Find the highest failure count
    computeMaxFailures() ;

    // Display Error Message for tasks with the highest failure count
    String jtUrl = null;
    try {
      jtUrl = JobTrackerURLResolver.getURL(conf);
    } catch (Exception e) {
      console.printError("Unable to retrieve URL for Hadoop Task logs. "
          + e.getMessage());
    }

    String msg = null;
    for (String task : failures.keySet()) {
      if (failures.get(task).intValue() == maxFailures) {
        TaskInfo ti = taskIdToInfo.get(task);
        String jobId = ti.getJobId();
        String taskUrl = (jtUrl == null) ? null :
          jtUrl + "/taskdetails.jsp?jobid=" + jobId + "&tipid=" + task.toString();

        TaskLogProcessor tlp = new TaskLogProcessor(conf);
        for (String logUrl : ti.getLogUrls()) {
          tlp.addTaskAttemptLogUrl(logUrl);
        }

        if (HiveConf.getBoolVar(conf, HiveConf.ConfVars.JOB_DEBUG_CAPTURE_STACKTRACES) &&
            stackTraces != null) {
          if (!stackTraces.containsKey(jobId)) {
            stackTraces.put(jobId, new ArrayList<List<String>>());
          }
          stackTraces.get(jobId).addAll(tlp.getStackTraces());
        }

        if (HiveConf.getBoolVar(conf, HiveConf.ConfVars.SHOW_JOB_FAIL_DEBUG_INFO)) {
          List<ErrorAndSolution> errors = tlp.getErrors();

          StringBuilder sb = new StringBuilder();
          // We use a StringBuilder and then call printError only once as
          // printError will write to both stderr and the error log file. In
          // situations where both the stderr and the log file output is
          // simultaneously output to a single stream, this will look cleaner.
          sb.append("\n");
          sb.append("Task with the most failures(" + maxFailures + "): \n");
          sb.append("-----\n");
          sb.append("Task ID:\n  " + task + "\n\n");
          if (taskUrl != null) {
            sb.append("URL:\n  " + taskUrl + "\n");
          }

          for (ErrorAndSolution e : errors) {
            sb.append("\n");
            sb.append("Possible error:\n  " + e.getError() + "\n\n");
            sb.append("Solution:\n  " + e.getSolution() + "\n");
          }
          sb.append("-----\n");

          sb.append("Diagnostic Messages for this Task:\n");
          String[] diagMesgs = ti.getDiagnosticMesgs();
          for (String mesg : diagMesgs) {
            sb.append(mesg + "\n");
          }
          msg = sb.toString();
          console.printError(msg);
        }

        // Only print out one task because that's good enough for debugging.
        break;
      }
    }
    return msg;
  }
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