private void getTaskInfos() throws IOException, MalformedURLException {
      int startIndex = 0;
      while (true) {
        TaskCompletionEvent[] taskCompletions = rj.getTaskCompletionEvents(startIndex);

        if (taskCompletions == null || taskCompletions.length == 0) {
          break;
        }

        boolean more = true;
        boolean firstError = true;
        for (TaskCompletionEvent t : taskCompletions) {
          // For each task completion event, get the associated task id, job id
          // and the logs
          String taskId = t.getTaskAttemptId().getTaskID().toString();
          String jobId = t.getTaskAttemptId().getJobID().toString();
          if (firstError) {
            console.printError("Examining task ID: " + taskId + " (and more) from job " + jobId);
            firstError = false;
          }

          TaskInfo ti = taskIdToInfo.get(taskId);
          if (ti == null) {
            ti = new TaskInfo(jobId);
            taskIdToInfo.put(taskId, ti);
          }
          // These tasks should have come from the same job.
          assert (ti.getJobId() != null &&  ti.getJobId().equals(jobId));
          String taskAttemptLogUrl = ShimLoader.getHadoopShims().getTaskAttemptLogUrl(
            conf, t.getTaskTrackerHttp(), t.getTaskId());
          if (taskAttemptLogUrl != null) {
            ti.getLogUrls().add(taskAttemptLogUrl);
          }

          // If a task failed, fetch its error code (if available).
          // Also keep track of the total number of failures for that
          // task (typically, a task gets re-run up to 4 times if it fails.
          if (t.getTaskStatus() != TaskCompletionEvent.Status.SUCCEEDED) {
            String[] diags = rj.getTaskDiagnostics(t.getTaskAttemptId());
            ti.setDiagnosticMesgs(diags);
            if (ti.getErrorCode() == 0) {
              ti.setErrorCode(extractErrorCode(diags));
            }

            Integer failAttempts = failures.get(taskId);
            if (failAttempts == null) {
              failAttempts = Integer.valueOf(0);
            }
            failAttempts = Integer.valueOf(failAttempts.intValue() + 1);
            failures.put(taskId, failAttempts);
          } else {
            successes.add(taskId);
          }
        }
        if (!more) {
          break;
        }
        startIndex += taskCompletions.length;
      }
    }
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