Hadoop之Yarn源码解析（四）

5、Yarn源码解析

工作机制

源码解析启动流程

5.1、 Yarn客户端向RM提交作业

1）在wordcount程序的驱动类中点击

	Job.java
boolean result = job.waitForCompletion(true);

public boolean waitForCompletion(boolean verbose
                                 ) throws IOException, InterruptedException,
                                          ClassNotFoundException {
  if (state == JobState.DEFINE) {
    submit();
  }
  if (verbose) {
    monitorAndPrintJob();
  } else {
    // get the completion poll interval from the client.
    int completionPollIntervalMillis = 
      Job.getCompletionPollInterval(cluster.getConf());
    while (!isComplete()) {
      try {
        Thread.sleep(completionPollIntervalMillis);
      } catch (InterruptedException ie) {
      }
    }
  }
  return isSuccessful();
}

public void submit() 
       throws IOException, InterruptedException, ClassNotFoundException {
  ensureState(JobState.DEFINE);
  setUseNewAPI();
  connect();
  final JobSubmitter submitter = 
      getJobSubmitter(cluster.getFileSystem(), cluster.getClient());
  status = ugi.doAs(new PrivilegedExceptionAction<JobStatus>() {
    public JobStatus run() throws IOException, InterruptedException, 
    ClassNotFoundException {
      return submitter.submitJobInternal(Job.this, cluster);
    }
  });
  state = JobState.RUNNING;
  LOG.info("The url to track the job: " + getTrackingURL());
 }
点击submitJobInternal()
JobSubmitter.java
JobStatus submitJobInternal(Job job, Cluster cluster) 
  throws ClassNotFoundException, InterruptedException, IOException {
  ... ...
  status = submitClient.submitJob(
          jobId, submitJobDir.toString(), job.getCredentials()); 
  ... ...
}

public JobStatus submitJob(JobID jobId, String jobSubmitDir, Credentials ts) throws IOException, InterruptedException;

2）创建提交环境

• ctrl + alt +B 查找submitJob实现类，YARNRunner.java

public JobStatus submitJob(JobID jobId, String jobSubmitDir, Credentials ts)
throws IOException, InterruptedException {
  
  addHistoryToken(ts);
  // 创建提交环境：
  ApplicationSubmissionContext appContext =
    createApplicationSubmissionContext(conf, jobSubmitDir, ts);

  // Submit to ResourceManager
  try {
    // 向RM提交一个应用程序，appContext里面封装了启动mrappMaster和运行container的命令
    ApplicationId applicationId =
        resMgrDelegate.submitApplication(appContext);
		
    // 获取提交响应
    ApplicationReport appMaster = resMgrDelegate
        .getApplicationReport(applicationId);
		
    String diagnostics =
        (appMaster == null ?
            "application report is null" : appMaster.getDiagnostics());
    if (appMaster == null
        || appMaster.getYarnApplicationState() == YarnApplicationState.FAILED
        || appMaster.getYarnApplicationState() == YarnApplicationState.KILLED) {
      throw new IOException("Failed to run job : " +
          diagnostics);
    }
    return clientCache.getClient(jobId).getJobStatus(jobId);
  } catch (YarnException e) {
    throw new IOException(e);
  }
}

public ApplicationSubmissionContext createApplicationSubmissionContext(
    Configuration jobConf, String jobSubmitDir, Credentials ts)
    throws IOException {
  ApplicationId applicationId = resMgrDelegate.getApplicationId();

  // Setup LocalResources
  // 封装了本地资源相关路径
  Map<String, LocalResource> localResources =
      setupLocalResources(jobConf, jobSubmitDir);

  // Setup security tokens
  DataOutputBuffer dob = new DataOutputBuffer();
  ts.writeTokenStorageToStream(dob);
  ByteBuffer securityTokens =
      ByteBuffer.wrap(dob.getData(), 0, dob.getLength());

  // Setup ContainerLaunchContext for AM container
  // 封装了启动mrappMaster和运行container的命令
  List<String> vargs = setupAMCommand(jobConf);
  ContainerLaunchContext amContainer = setupContainerLaunchContextForAM(
      jobConf, localResources, securityTokens, vargs);

  ... ...

  return appContext;
}

private List<String> setupAMCommand(Configuration jobConf) {
  List<String> vargs = new ArrayList<>(8);
  // Java进程启动命令开始
  vargs.add(MRApps.crossPlatformifyMREnv(jobConf, Environment.JAVA_HOME)
      + "/bin/java");

  Path amTmpDir =
      new Path(MRApps.crossPlatformifyMREnv(conf, Environment.PWD),
          YarnConfiguration.DEFAULT_CONTAINER_TEMP_DIR);
  vargs.add("-Djava.io.tmpdir=" + amTmpDir);
  MRApps.addLog4jSystemProperties(null, vargs, conf);

  // Check for Java Lib Path usage in MAP and REDUCE configs
  warnForJavaLibPath(conf.get(MRJobConfig.MAP_JAVA_OPTS, ""),
      "map",
      MRJobConfig.MAP_JAVA_OPTS,
      MRJobConfig.MAP_ENV);
  warnForJavaLibPath(conf.get(MRJobConfig.MAPRED_MAP_ADMIN_JAVA_OPTS, ""),
      "map",
      MRJobConfig.MAPRED_MAP_ADMIN_JAVA_OPTS,
      MRJobConfig.MAPRED_ADMIN_USER_ENV);
  warnForJavaLibPath(conf.get(MRJobConfig.REDUCE_JAVA_OPTS, ""),
      "reduce",
      MRJobConfig.REDUCE_JAVA_OPTS,
      MRJobConfig.REDUCE_ENV);
  warnForJavaLibPath(conf.get(MRJobConfig.MAPRED_REDUCE_ADMIN_JAVA_OPTS, ""),
      "reduce",
      MRJobConfig.MAPRED_REDUCE_ADMIN_JAVA_OPTS,
      MRJobConfig.MAPRED_ADMIN_USER_ENV);

  // Add AM admin command opts before user command opts
  // so that it can be overridden by user
  String mrAppMasterAdminOptions = conf.get(MRJobConfig.MR_AM_ADMIN_COMMAND_OPTS,
      MRJobConfig.DEFAULT_MR_AM_ADMIN_COMMAND_OPTS);
  warnForJavaLibPath(mrAppMasterAdminOptions, "app master",
      MRJobConfig.MR_AM_ADMIN_COMMAND_OPTS, MRJobConfig.MR_AM_ADMIN_USER_ENV);
  vargs.add(mrAppMasterAdminOptions);

  // Add AM user command opts 用户命令参数
  String mrAppMasterUserOptions = conf.get(MRJobConfig.MR_AM_COMMAND_OPTS,
      MRJobConfig.DEFAULT_MR_AM_COMMAND_OPTS);
  warnForJavaLibPath(mrAppMasterUserOptions, "app master",
      MRJobConfig.MR_AM_COMMAND_OPTS, MRJobConfig.MR_AM_ENV);
  vargs.add(mrAppMasterUserOptions);

  if (jobConf.getBoolean(MRJobConfig.MR_AM_PROFILE,
      MRJobConfig.DEFAULT_MR_AM_PROFILE)) {
    final String profileParams = jobConf.get(MRJobConfig.MR_AM_PROFILE_PARAMS,
        MRJobConfig.DEFAULT_TASK_PROFILE_PARAMS);
    if (profileParams != null) {
      vargs.add(String.format(profileParams,
          ApplicationConstants.LOG_DIR_EXPANSION_VAR + Path.SEPARATOR
              + TaskLog.LogName.PROFILE));
    }
  }

  // 封装了要启动的mrappmaster全类名 
  // org.apache.hadoop.mapreduce.v2.app.MRAppMaster
  vargs.add(MRJobConfig.APPLICATION_MASTER_CLASS);
  vargs.add("1>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR +
      Path.SEPARATOR + ApplicationConstants.STDOUT);
  vargs.add("2>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR +
      Path.SEPARATOR + ApplicationConstants.STDERR);
  return vargs;
}

3）向Yarn提交

• 点击submitJob方法中的submitApplication()

YARNRunner.java
ApplicationId applicationId = 
resMgrDelegate.submitApplication(appContext);

public ApplicationId
    submitApplication(ApplicationSubmissionContext appContext)
        throws YarnException, IOException {
  return client.submitApplication(appContext);
}
ctrl + alt +B 查找submitApplication实现类，YarnClientImpl.java
public ApplicationId
    submitApplication(ApplicationSubmissionContext appContext)
        throws YarnException, IOException {
  ApplicationId applicationId = appContext.getApplicationId();
  if (applicationId == null) {
    throw new ApplicationIdNotProvidedException(
        "ApplicationId is not provided in ApplicationSubmissionContext");
  }
  // 创建一个提交请求
  SubmitApplicationRequest request =
      Records.newRecord(SubmitApplicationRequest.class);
  request.setApplicationSubmissionContext(appContext);
  ... ...

  //TODO: YARN-1763:Handle RM failovers during the submitApplication call.
  // 继续提交，实现类是ApplicationClientProtocolPBClientImpl
  rmClient.submitApplication(request);

  int pollCount = 0;
  long startTime = System.currentTimeMillis();
  EnumSet<YarnApplicationState> waitingStates = 
                               EnumSet.of(YarnApplicationState.NEW,
                               YarnApplicationState.NEW_SAVING,
                               YarnApplicationState.SUBMITTED);
  EnumSet<YarnApplicationState> failToSubmitStates = 
                                EnumSet.of(YarnApplicationState.FAILED,
                                YarnApplicationState.KILLED);		
  while (true) {
    try {
	  // 获取提交给Yarn的反馈
      ApplicationReport appReport = getApplicationReport(applicationId);
      YarnApplicationState state = appReport.getYarnApplicationState();
      ... ...
    } catch (ApplicationNotFoundException ex) {
      // FailOver or RM restart happens before RMStateStore saves
      // ApplicationState
      LOG.info("Re-submit application " + applicationId + "with the " +
          "same ApplicationSubmissionContext");
	  // 如果提交失败，则再次提交
      rmClient.submitApplication(request);
    }
  }

  return applicationId;
}
ctrl + alt +B 查找submitApplication实现类，ClientRMService.java
public SubmitApplicationResponse submitApplication(
    SubmitApplicationRequest request) throws YarnException, IOException {
  ApplicationSubmissionContext submissionContext = request
      .getApplicationSubmissionContext();
  ApplicationId applicationId = submissionContext.getApplicationId();
  CallerContext callerContext = CallerContext.getCurrent();

  ... ...

  try {
    // call RMAppManager to submit application directly
    rmAppManager.submitApplication(submissionContext,
        System.currentTimeMillis(), user);

    LOG.info("Application with id " + applicationId.getId() + 
        " submitted by user " + user);
    RMAuditLogger.logSuccess(user, AuditConstants.SUBMIT_APP_REQUEST,
        "ClientRMService", applicationId, callerContext,
        submissionContext.getQueue());
  } catch (YarnException e) {
    LOG.info("Exception in submitting " + applicationId, e);
    RMAuditLogger.logFailure(user, AuditConstants.SUBMIT_APP_REQUEST,
        e.getMessage(), "ClientRMService",
        "Exception in submitting application", applicationId, callerContext,
        submissionContext.getQueue());
    throw e;
  }

  return recordFactory
      .newRecordInstance(SubmitApplicationResponse.class);
}

5.2、 RM启动MRAppMaster

0）在pom.xml中增加如下依赖

<dependency>
    <groupId>org.apache.hadoopgroupId>
    <artifactId>hadoop-mapreduce-client-appartifactId>
    <version>3.1.3version>
dependency>

• ctrl +n 查找MRAppMaster，搜索main方法

public static void main(String[] args) {
  try {
    ... ...

	// 初始化一个container
    ContainerId containerId = ContainerId.fromString(containerIdStr);
    ApplicationAttemptId applicationAttemptId =
        containerId.getApplicationAttemptId();
    if (applicationAttemptId != null) {
      CallerContext.setCurrent(new CallerContext.Builder(
          "mr_appmaster_" + applicationAttemptId.toString()).build());
    }
    long appSubmitTime = Long.parseLong(appSubmitTimeStr);
    
    // 创建appMaster对象
    MRAppMaster appMaster =
        new MRAppMaster(applicationAttemptId, containerId, nodeHostString,
            Integer.parseInt(nodePortString),
            Integer.parseInt(nodeHttpPortString), appSubmitTime);
    ... ...
	
	// 初始化并启动AppMaster
    initAndStartAppMaster(appMaster, conf, jobUserName);
  } catch (Throwable t) {
    LOG.error("Error starting MRAppMaster", t);
    ExitUtil.terminate(1, t);
  }
}

protected static void initAndStartAppMaster(final MRAppMaster appMaster,
    final JobConf conf, String jobUserName) throws IOException,
    InterruptedException {
  ... ...
  conf.getCredentials().addAll(credentials);
  appMasterUgi.doAs(new PrivilegedExceptionAction<Object>() {
    @Override
    public Object run() throws Exception {
	  // 初始化
      appMaster.init(conf);
	  // 启动
      appMaster.start();
      if(appMaster.errorHappenedShutDown) {
        throw new IOException("Was asked to shut down.");
      }
      return null;
    }
  });
}

public void init(Configuration conf) {
  ... ...
  synchronized (stateChangeLock) {
    if (enterState(STATE.INITED) != STATE.INITED) {
      setConfig(conf);
      try {
	    // 调用MRAppMaster中的serviceInit()方法
        serviceInit(config);
        if (isInState(STATE.INITED)) {
          //if the service ended up here during init,
          //notify the listeners
		  // 如果初始化完成，通知监听器
          notifyListeners();
        }
      } catch (Exception e) {
        noteFailure(e);
        ServiceOperations.stopQuietly(LOG, this);
        throw ServiceStateException.convert(e);
      }
    }
  }
}

• ctrl + alt +B 查找serviceInit实现类，MRAppMaster.java

protected void serviceInit(final Configuration conf) throws Exception {
  ... ...
  // 创建提交路径
  clientService = createClientService(context);
  
  // 创建调度器
  clientService.init(conf);
  
  // 创建job提交RPC客户端
  containerAllocator = createContainerAllocator(clientService, context);
  ... ...
}
点击MRAppMaster.java 中的initAndStartAppMaster 方法中的appMaster.start();
public void start() {
  if (isInState(STATE.STARTED)) {
    return;
  }
  //enter the started state
  synchronized (stateChangeLock) {
    if (stateModel.enterState(STATE.STARTED) != STATE.STARTED) {
      try {
        startTime = System.currentTimeMillis();
		// 调用MRAppMaster中的serviceStart()方法
        serviceStart();
        if (isInState(STATE.STARTED)) {
          //if the service started (and isn't now in a later state), notify
          LOG.debug("Service {} is started", getName());
          notifyListeners();
        }
      } catch (Exception e) {
        noteFailure(e);
        ServiceOperations.stopQuietly(LOG, this);
        throw ServiceStateException.convert(e);
      }
    }
  }
}

protected void serviceStart() throws Exception {
  ... ...
  if (initFailed) {
    JobEvent initFailedEvent = new JobEvent(job.getID(), JobEventType.JOB_INIT_FAILED);
    jobEventDispatcher.handle(initFailedEvent);
  } else {
    // All components have started, start the job.
	// 初始化成功后，提交Job到队列中
    startJobs();
  }
}

protected void startJobs() {
  /** create a job-start event to get this ball rolling */
  JobEvent startJobEvent = new JobStartEvent(job.getID(),
      recoveredJobStartTime);
  /** send the job-start event. this triggers the job execution. */
  // 这里将job存放到yarn队列
  // dispatcher = AsyncDispatcher
  // getEventHandler()返回的是GenericEventHandler
  dispatcher.getEventHandler().handle(startJobEvent);
}
ctrl + alt +B 查找handle实现类，GenericEventHandler.java
class GenericEventHandler implements EventHandler<Event> {
  public void handle(Event event) {
    ... ...
    try {
	  // 将job存储到yarn队列中
      eventQueue.put(event);
    } catch (InterruptedException e) {
      ... ...
    }
  };
}

5.3、 调度器任务执行（YarnChild）

1）启动MapTask

• ctrl +n 查找YarnChild，搜索main方法

public static void main(String[] args) throws Throwable {
  Thread.setDefaultUncaughtExceptionHandler(new YarnUncaughtExceptionHandler());
  LOG.debug("Child starting");

  ... ...

  task = myTask.getTask();
  YarnChild.taskid = task.getTaskID();
  ... ...

  // Create a final reference to the task for the doAs block
  final Task taskFinal = task;
  childUGI.doAs(new PrivilegedExceptionAction<Object>() {
      @Override
      public Object run() throws Exception {
        // use job-specified working directory
        setEncryptedSpillKeyIfRequired(taskFinal);
        FileSystem.get(job).setWorkingDirectory(job.getWorkingDirectory());
		// 调用task执行（maptask或者reducetask）
        taskFinal.run(job, umbilical); // run the task
        return null;
      }
    });
  } 
  ... ...
}

• ctrl + alt +B 查找run实现类，maptask.java

public void run(final JobConf job, final TaskUmbilicalProtocol umbilical)
  throws IOException, ClassNotFoundException, InterruptedException {
  this.umbilical = umbilical;

  // 判断是否是MapTask
  if (isMapTask()) {
    // If there are no reducers then there won't be any sort. Hence the map 
    // phase will govern the entire attempt's progress.
	// 如果reducetask个数为零，maptask占用整个任务的100%
    if (conf.getNumReduceTasks() == 0) {
      mapPhase = getProgress().addPhase("map", 1.0f);
    } else {
      // If there are reducers then the entire attempt's progress will be 
      // split between the map phase (67%) and the sort phase (33%).
	  // 如果reduceTask个数不为零，MapTask占用整个任务的66.7% sort阶段占比
      mapPhase = getProgress().addPhase("map", 0.667f);
      sortPhase  = getProgress().addPhase("sort", 0.333f);
    }
  }
  ... ...
  if (useNewApi) {
    // 调用新的API执行maptask
    runNewMapper(job, splitMetaInfo, umbilical, reporter);
  } else {
    runOldMapper(job, splitMetaInfo, umbilical, reporter);
  }
  done(umbilical, reporter);
}

void runNewMapper(final JobConf job,
                  final TaskSplitIndex splitIndex,
                  final TaskUmbilicalProtocol umbilical,
                  TaskReporter reporter
                  ) throws IOException, ClassNotFoundException,
                           InterruptedException {
  ... ...

  try {
    input.initialize(split, mapperContext);
	// 运行maptask
    mapper.run(mapperContext);
	
    mapPhase.complete();
    setPhase(TaskStatus.Phase.SORT);
    statusUpdate(umbilical);
    input.close();
    input = null;
    output.close(mapperContext);
    output = null;
  } finally {
    closeQuietly(input);
    closeQuietly(output, mapperContext);
  }
}
Mapper.java（和Map联系在一起）
public void run(Context context) throws IOException, InterruptedException {
  setup(context);
  try {
    while (context.nextKeyValue()) {
      map(context.getCurrentKey(), context.getCurrentValue(), context);
    }
  } finally {
    cleanup(context);
  }
}

2）启动ReduceTask

• 在YarnChild.java类中的main方法中ctrl + alt +B 查找run实现类，reducetask.java

public void run(JobConf job, final TaskUmbilicalProtocol umbilical)
  throws IOException, InterruptedException, ClassNotFoundException {
  job.setBoolean(JobContext.SKIP_RECORDS, isSkipping());

  ... ...

  if (useNewApi) {
	// 调用新API执行reduce
    runNewReducer(job, umbilical, reporter, rIter, comparator, 
                  keyClass, valueClass);
  } else {
    runOldReducer(job, umbilical, reporter, rIter, comparator, 
                  keyClass, valueClass);
  }

  shuffleConsumerPlugin.close();
  done(umbilical, reporter);
}

void runNewReducer(JobConf job,
                   final TaskUmbilicalProtocol umbilical,
                   final TaskReporter reporter,
                   RawKeyValueIterator rIter,
                   RawComparator<INKEY> comparator,
                   Class<INKEY> keyClass,
                   Class<INVALUE> valueClass
                   ) throws IOException,InterruptedException, 
                            ClassNotFoundException {
  ... ...
  try {
    // 调用reducetask的run方法
    reducer.run(reducerContext);
  } finally {
    trackedRW.close(reducerContext);
  }
}
Reduce.java
public void run(Context context) throws IOException, InterruptedException {
  setup(context);
  try {
    while (context.nextKey()) {
      reduce(context.getCurrentKey(), context.getValues(), context);
      // If a back up store is used, reset it
      Iterator<VALUEIN> iter = context.getValues().iterator();
      if(iter instanceof ReduceContext.ValueIterator) {
        ((ReduceContext.ValueIterator<VALUEIN>)iter).resetBackupStore();        
      }
    }
  } finally {
    cleanup(context);
  }
}