import org.apache.hadoop.mapreduce.jobhistory.EventReader; //导入依赖的package包/类
private List<AMInfo> readJustAMInfos() {
  List<AMInfo> amInfos = new ArrayList<AMInfo>();
  FSDataInputStream inputStream = null;
  try {
    inputStream = getPreviousJobHistoryStream(getConfig(), appAttemptID);
    EventReader jobHistoryEventReader = new EventReader(inputStream);

    // All AMInfos are contiguous. Track when the first AMStartedEvent
    // appears.
    boolean amStartedEventsBegan = false;

    HistoryEvent event;
    while ((event = jobHistoryEventReader.getNextEvent()) != null) {
      if (event.getEventType() == EventType.AM_STARTED) {
        if (!amStartedEventsBegan) {
          // First AMStartedEvent.
          amStartedEventsBegan = true;
        }
        AMStartedEvent amStartedEvent = (AMStartedEvent) event;
        amInfos.add(MRBuilderUtils.newAMInfo(
          amStartedEvent.getAppAttemptId(), amStartedEvent.getStartTime(),
          amStartedEvent.getContainerId(),
          StringInterner.weakIntern(amStartedEvent.getNodeManagerHost()),
          amStartedEvent.getNodeManagerPort(),
          amStartedEvent.getNodeManagerHttpPort()));
      } else if (amStartedEventsBegan) {
        // This means AMStartedEvents began and this event is a
        // non-AMStarted event.
        // No need to continue reading all the other events.
        break;
      }
    }
  } catch (IOException e) {
    LOG.warn("Could not parse the old history file. "
        + "Will not have old AMinfos ", e);
  } finally {
    if (inputStream != null) {
      IOUtils.closeQuietly(inputStream);
    }
  }
  return amInfos;
}
 

import org.apache.hadoop.mapreduce.jobhistory.EventReader; //导入依赖的package包/类
@Test
public void testMultipleFailedTasks() throws Exception {
  JobHistoryParser parser =
      new JobHistoryParser(Mockito.mock(FSDataInputStream.class));
  EventReader reader = Mockito.mock(EventReader.class);
  final AtomicInteger numEventsRead = new AtomicInteger(0); // Hack!
  final org.apache.hadoop.mapreduce.TaskType taskType =
      org.apache.hadoop.mapreduce.TaskType.MAP;
  final TaskID[] tids = new TaskID[2];
  final JobID jid = new JobID("1", 1);
  tids[0] = new TaskID(jid, taskType, 0);
  tids[1] = new TaskID(jid, taskType, 1);
  Mockito.when(reader.getNextEvent()).thenAnswer(
      new Answer<HistoryEvent>() {
        public HistoryEvent answer(InvocationOnMock invocation)
            throws IOException {
          // send two task start and two task fail events for tasks 0 and 1
          int eventId = numEventsRead.getAndIncrement();
          TaskID tid = tids[eventId & 0x1];
          if (eventId < 2) {
            return new TaskStartedEvent(tid, 0, taskType, "");
          }
          if (eventId < 4) {
            TaskFailedEvent tfe = new TaskFailedEvent(tid, 0, taskType,
                "failed", "FAILED", null, new Counters());
            tfe.setDatum(tfe.getDatum());
            return tfe;
          }
          if (eventId < 5) {
            JobUnsuccessfulCompletionEvent juce =
                new JobUnsuccessfulCompletionEvent(jid, 100L, 2, 0,
                    "JOB_FAILED", Collections.singletonList(
                        "Task failed: " + tids[0].toString()));
            return juce;
          }
          return null;
        }
      });
  JobInfo info = parser.parse(reader);
  assertTrue("Task 0 not implicated",
      info.getErrorInfo().contains(tids[0].toString()));
}
 

import org.apache.hadoop.mapreduce.jobhistory.EventReader; //导入依赖的package包/类
public CurrentJHParser(InputStream input) throws IOException {
  reader = new EventReader(new DataInputStream(input));
}