Hadoop2.0 客户端提交作业流程

YARN作业提交的客户端仍然使用RunJar类，和MR1一样，可参考 
http://blog.csdn.net/lihm0_1/article/details/13629375
在1.x中是向JobTracker提交，而在2.x中换成了ResourceManager，客户端的代理对象也有所变动，换成了YarnRunner，但大致流程和1类似，主要的流程集中在JobSubmitter.submitJobInternal中，包括检测输出目录合法性，设置作业提交信息（主机和用户），获得JobID，向HDFS中拷贝作业所需文件（Job.jar Job.xml split文件等）最有执行作业提交。这里仍然以WordCount为例介绍提交流程.

public static void main(String[] args) throws Exception {
    // 创建一个job
    Configuration conf = new Configuration();
    conf.set("mapreduce.job.queuename", "p1");

    @SuppressWarnings("deprecation")
        Job job = new Job(conf, "WordCount");
    job.setJarByClass(WordCount.class);
    job.setJar("/root/wordcount-2.3.0.jar");


    // 设置输入输出类型
    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(IntWritable.class);


    // 设置map和reduce类
    job.setMapperClass(WordCountMapper.class);
    job.setReducerClass(WordCountReduce.class);


    // 设置输入输出流
    FileInputFormat.addInputPath(job, new Path("/tmp/a.txt"));
    FileOutputFormat.setOutputPath(job, new Path("/tmp/output"));


    job.waitForCompletion(true);//此处进入作业提交流程，然后循环监控作业状态
}

此处和1.x相同，提交作业，循环监控作业状态

public boolean waitForCompletion(boolean verbose
                                 ) throws IOException, InterruptedException,
                                          ClassNotFoundException {
  if (state == JobState.DEFINE) {
    submit();//提交
  }
  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();
}

主要分析submit函数，来看作业是如何提交的，此处已经和1.x不同。但仍分为两个阶段1、连接master 2、作业提交

public void submit()
       throws IOException, InterruptedException, ClassNotFoundException {
  ensureState(JobState.DEFINE);
  setUseNewAPI();
  //连接RM
  connect();
  final JobSubmitter submitter =
      getJobSubmitter(cluster.getFileSystem(), cluster.getClient());
  status = ugi.doAs(new PrivilegedExceptionAction<JobStatus>() {
    public JobStatus run() throws IOException, InterruptedException,
    ClassNotFoundException {
        //提交作业
      return submitter.submitJobInternal(Job.this, cluster);
    }
  });
  state = JobState.RUNNING;
  LOG.info("The url to track the job: " + getTrackingURL());
}

连接master时会建立Cluster实例，下面是Cluster构造函数，其中重点初始化部分

public Cluster(InetSocketAddress jobTrackAddr, Configuration conf)
    throws IOException {
  this.conf = conf;
  this.ugi = UserGroupInformation.getCurrentUser();
  initialize(jobTrackAddr, conf);
}

创建客户端代理阶段用到了java.util.ServiceLoader,目前2.3.0版本包含两个LocalClientProtocolProvider（本地作业） YarnClientProtocolProvider（Yarn作业），此处会根据mapreduce.framework.name的配置创建相应的客户端

private void initialize(InetSocketAddress jobTrackAddr, Configuration conf)
    throws IOException {


  synchronized (frameworkLoader) {
    for (ClientProtocolProvider provider : frameworkLoader) {
      LOG.debug("Trying ClientProtocolProvider : "
          + provider.getClass().getName());
      ClientProtocol clientProtocol = null;
      try {
        if (jobTrackAddr == null) {
            //创建YARNRunner对象
          clientProtocol = provider.create(conf);
        } else {
          clientProtocol = provider.create(jobTrackAddr, conf);
        }
                //初始化Cluster内部成员变量
        if (clientProtocol != null) {
          clientProtocolProvider = provider;
          client = clientProtocol;
          LOG.debug("Picked " + provider.getClass().getName()
              + " as the ClientProtocolProvider");
          break;
        }
        else {
          LOG.debug("Cannot pick " + provider.getClass().getName()
              + " as the ClientProtocolProvider - returned null protocol");
        }
      }
      catch (Exception e) {
        LOG.info("Failed to use " + provider.getClass().getName()
            + " due to error: " + e.getMessage());
      }
    }
  }
    //异常处理，如果此处出现异常，则证明加载的jar包有问题，YarnRunner所处的jar不存在？
  if (null == clientProtocolProvider || null == client) {
    throw new IOException(
        "Cannot initialize Cluster. Please check your configuration for "
            + MRConfig.FRAMEWORK_NAME
            + " and the correspond server addresses.");
  }
}

provider创建代理实际是创建了一个YranRunner对象，因为我们这里提交的不是Local的，而是Yarn作业

@Override
public ClientProtocol create(Configuration conf) throws IOException {
  if (MRConfig.YARN_FRAMEWORK_NAME.equals(conf.get(MRConfig.FRAMEWORK_NAME))) {
    return new YARNRunner(conf);
  }
  return null;
}

创建客户端代理的流程如下：
Cluster->ClientProtocol(YarnRunner)->ResourceMgrDelegate->client(YarnClientImpl)->rmClient(ApplicationClientProtocol)
在YarnClientImpl的serviceStart阶段会创建RPC代理，注意其中的协议。

protected void serviceStart() throws Exception {
  try {
    rmClient = ClientRMProxy.createRMProxy(getConfig(),
          ApplicationClientProtocol.class);
  } catch (IOException e) {
    throw new YarnRuntimeException(e);
  }
  super.serviceStart();
}

YarnRunner的构造函数如下：

public YARNRunner(Configuration conf, ResourceMgrDelegate resMgrDelegate,
    ClientCache clientCache) {
  this.conf = conf;
  try {
    this.resMgrDelegate = resMgrDelegate;
    this.clientCache = clientCache;
    this.defaultFileContext = FileContext.getFileContext(this.conf);
  } catch (UnsupportedFileSystemException ufe) {
    throw new RuntimeException("Error in instantiating YarnClient", ufe);
  }
}

下面看最核心的提交部分JobSubmitter.submitJobInternal

JobStatus submitJobInternal(Job job, Cluster cluster)
throws ClassNotFoundException, InterruptedException, IOException {


  //检测输出目录合法性，是否已存在，或未设置
  checkSpecs(job);


  Configuration conf = job.getConfiguration();
  addMRFrameworkToDistributedCache(conf);
    //获得登录区，用以存放作业执行过程中用到的文件，默认位置/tmp/hadoop-yarn/staging/root/.staging ，可通过yarn.app.mapreduce.am.staging-dir修改
  Path jobStagingArea = JobSubmissionFiles.getStagingDir(cluster, conf);
  //主机名和地址设置
  InetAddress ip = InetAddress.getLocalHost();
  if (ip != null) {
    submitHostAddress = ip.getHostAddress();
    submitHostName = ip.getHostName();
    conf.set(MRJobConfig.JOB_SUBMITHOST,submitHostName);
    conf.set(MRJobConfig.JOB_SUBMITHOSTADDR,submitHostAddress);
  }
  //获取新的JobID，此处需要RPC调用
  JobID jobId = submitClient.getNewJobID();
  job.setJobID(jobId);
  //获取提交目录：/tmp/hadoop-yarn/staging/root/.staging/job_1395778831382_0002
  Path submitJobDir = new Path(jobStagingArea, jobId.toString());
  JobStatus status = null;
  try {
    conf.set(MRJobConfig.USER_NAME,
        UserGroupInformation.getCurrentUser().getShortUserName());
    conf.set("hadoop.http.filter.initializers",
        "org.apache.hadoop.yarn.server.webproxy.amfilter.AmFilterInitializer");
    conf.set(MRJobConfig.MAPREDUCE_JOB_DIR, submitJobDir.toString());
    LOG.debug("Configuring job " + jobId + " with " + submitJobDir
        + " as the submit dir");
    // get delegation token for the dir
    TokenCache.obtainTokensForNamenodes(job.getCredentials(),
        new Path[] { submitJobDir }, conf);

    populateTokenCache(conf, job.getCredentials());


    // generate a secret to authenticate shuffle transfers
    if (TokenCache.getShuffleSecretKey(job.getCredentials()) == null) {
      KeyGenerator keyGen;
      try {
        keyGen = KeyGenerator.getInstance(SHUFFLE_KEYGEN_ALGORITHM);
        keyGen.init(SHUFFLE_KEY_LENGTH);
      } catch (NoSuchAlgorithmException e) {
        throw new IOException("Error generating shuffle secret key", e);
      }
      SecretKey shuffleKey = keyGen.generateKey();
      TokenCache.setShuffleSecretKey(shuffleKey.getEncoded(),
          job.getCredentials());
    }
    //向集群中拷贝所需文件，下面会单独分析（1）
    copyAndConfigureFiles(job, submitJobDir);
    Path submitJobFile = JobSubmissionFiles.getJobConfPath(submitJobDir);

    // 写分片文件job.split job.splitmetainfo，具体写入过程与MR1相同，可参考以前文章
    LOG.debug("Creating splits at " + jtFs.makeQualified(submitJobDir));
    int maps = writeSplits(job, submitJobDir);
    conf.setInt(MRJobConfig.NUM_MAPS, maps);
    LOG.info("number of splits:" + maps);


    // write "queue admins of the queue to which job is being submitted"
    // to job file.
    //设置队列名
    String queue = conf.get(MRJobConfig.QUEUE_NAME,
        JobConf.DEFAULT_QUEUE_NAME);
    AccessControlList acl = submitClient.getQueueAdmins(queue);
    conf.set(toFullPropertyName(queue,
        QueueACL.ADMINISTER_JOBS.getAclName()), acl.getAclString());


    // removing jobtoken referrals before copying the jobconf to HDFS
    // as the tasks don't need this setting, actually they may break
    // because of it if present as the referral will point to a
    // different job.
    TokenCache.cleanUpTokenReferral(conf);


    if (conf.getBoolean(
        MRJobConfig.JOB_TOKEN_TRACKING_IDS_ENABLED,
        MRJobConfig.DEFAULT_JOB_TOKEN_TRACKING_IDS_ENABLED)) {
      // Add HDFS tracking ids
      ArrayList<String> trackingIds = new ArrayList<String>();
      for (Token<? extends TokenIdentifier> t :
          job.getCredentials().getAllTokens()) {
        trackingIds.add(t.decodeIdentifier().getTrackingId());
      }
      conf.setStrings(MRJobConfig.JOB_TOKEN_TRACKING_IDS,
          trackingIds.toArray(new String[trackingIds.size()]));
    }


    // Write job file to submit dir
    //写入job.xml
    writeConf(conf, submitJobFile);

    //
    // Now, actually submit the job (using the submit name)
    //这里才开始真正提交，见下面分析(2)
    printTokens(jobId, job.getCredentials());
    status = submitClient.submitJob(
        jobId, submitJobDir.toString(), job.getCredentials());
    if (status != null) {
      return status;
    } else {
      throw new IOException("Could not launch job");
    }
  } finally {
    if (status == null) {
      LOG.info("Cleaning up the staging area " + submitJobDir);
      if (jtFs != null && submitJobDir != null)
        jtFs.delete(submitJobDir, true);


    }
  }
}

（1）文件拷贝过程如下，默认副本数为10

private void copyAndConfigureFiles(Job job, Path jobSubmitDir)
throws IOException {
  Configuration conf = job.getConfiguration();
  short replication = (short)conf.getInt(Job.SUBMIT_REPLICATION, 10);
  //开始拷贝
  copyAndConfigureFiles(job, jobSubmitDir, replication);


  // Set the working directory
  if (job.getWorkingDirectory() == null) {
    job.setWorkingDirectory(jtFs.getWorkingDirectory());
  }


}

下面是具体文件拷贝过程，注释里写的也比较清楚了

// configures -files, -libjars and -archives.
private void copyAndConfigureFiles(Job job, Path submitJobDir,
    short replication) throws IOException {
  Configuration conf = job.getConfiguration();
  if (!(conf.getBoolean(Job.USED_GENERIC_PARSER, false))) {
    LOG.warn("Hadoop command-line option parsing not performed. " +
             "Implement the Tool interface and execute your application " +
             "with ToolRunner to remedy this.");
  }


  // get all the command line arguments passed in by the user conf
  String files = conf.get("tmpfiles");
  String libjars = conf.get("tmpjars");
  String archives = conf.get("tmparchives");
  String jobJar = job.getJar();


  //
  // Figure out what fs the JobTracker is using.  Copy the
  // job to it, under a temporary name.  This allows DFS to work,
  // and under the local fs also provides UNIX-like object loading
  // semantics.  (that is, if the job file is deleted right after
  // submission, we can still run the submission to completion)
  //


  // Create a number of filenames in the JobTracker's fs namespace
  LOG.debug("default FileSystem: " + jtFs.getUri());
  if (jtFs.exists(submitJobDir)) {
    throw new IOException("Not submitting job. Job directory " + submitJobDir
        +" already exists!! This is unexpected.Please check what's there in" +
        " that directory");
  }
  submitJobDir = jtFs.makeQualified(submitJobDir);
  submitJobDir = new Path(submitJobDir.toUri().getPath());
  FsPermission mapredSysPerms = new FsPermission(JobSubmissionFiles.JOB_DIR_PERMISSION);
  //创建工作目录
  FileSystem.mkdirs(jtFs, submitJobDir, mapredSysPerms);
  Path filesDir = JobSubmissionFiles.getJobDistCacheFiles(submitJobDir);
  Path archivesDir = JobSubmissionFiles.getJobDistCacheArchives(submitJobDir);
  Path libjarsDir = JobSubmissionFiles.getJobDistCacheLibjars(submitJobDir);
  // add all the command line files/ jars and archive
  // first copy them to jobtrackers filesystem
  //建立上述所需目录
  if (files != null) {
    FileSystem.mkdirs(jtFs, filesDir, mapredSysPerms);
    String[] fileArr = files.split(",");
    for (String tmpFile: fileArr) {
      URI tmpURI = null;
      try {
        tmpURI = new URI(tmpFile);
      } catch (URISyntaxException e) {
        throw new IllegalArgumentException(e);
      }
      Path tmp = new Path(tmpURI);
      Path newPath = copyRemoteFiles(filesDir, tmp, conf, replication);
      try {
        URI pathURI = getPathURI(newPath, tmpURI.getFragment());
        DistributedCache.addCacheFile(pathURI, conf);
      } catch(URISyntaxException ue) {
        //should not throw a uri exception
        throw new IOException("Failed to create uri for " + tmpFile, ue);
      }
    }
  }

  if (libjars != null) {
    FileSystem.mkdirs(jtFs, libjarsDir, mapredSysPerms);
    String[] libjarsArr = libjars.split(",");
    for (String tmpjars: libjarsArr) {
      Path tmp = new Path(tmpjars);
      Path newPath = copyRemoteFiles(libjarsDir, tmp, conf, replication);
      DistributedCache.addFileToClassPath(
          new Path(newPath.toUri().getPath()), conf);
    }
  }

  if (archives != null) {
    FileSystem.mkdirs(jtFs, archivesDir, mapredSysPerms);
    String[] archivesArr = archives.split(",");
    for (String tmpArchives: archivesArr) {
      URI tmpURI;
      try {
        tmpURI = new URI(tmpArchives);
      } catch (URISyntaxException e) {
        throw new IllegalArgumentException(e);
      }
      Path tmp = new Path(tmpURI);
      Path newPath = copyRemoteFiles(archivesDir, tmp, conf,
        replication);
      try {
        URI pathURI = getPathURI(newPath, tmpURI.getFragment());
        DistributedCache.addCacheArchive(pathURI, conf);
      } catch(URISyntaxException ue) {
        //should not throw an uri excpetion
        throw new IOException("Failed to create uri for " + tmpArchives, ue);
      }
    }
  }


  if (jobJar != null) {   // copy jar to JobTracker's fs
    // use jar name if job is not named.
    if ("".equals(job.getJobName())){
      job.setJobName(new Path(jobJar).getName());
    }
    Path jobJarPath = new Path(jobJar);
    URI jobJarURI = jobJarPath.toUri();
    // If the job jar is already in fs, we don't need to copy it from local fs
    if (jobJarURI.getScheme() == null || jobJarURI.getAuthority() == null
            || !(jobJarURI.getScheme().equals(jtFs.getUri().getScheme())
                && jobJarURI.getAuthority().equals(
                                          jtFs.getUri().getAuthority()))) {
      //拷贝wordcount.jar，注意拷贝过去后会重命名为job.jar，副本数为10
      copyJar(jobJarPath, JobSubmissionFiles.getJobJar(submitJobDir),
          replication);
      job.setJar(JobSubmissionFiles.getJobJar(submitJobDir).toString());
    }
  } else {
    LOG.warn("No job jar file set.  User classes may not be found. "+
    "See Job or Job#setJar(String).");
  }


  //  set the timestamps of the archives and files
  //  set the public/private visibility of the archives and files
  ClientDistributedCacheManager.determineTimestampsAndCacheVisibilities(conf);
  // get DelegationToken for each cached file
  ClientDistributedCacheManager.getDelegationTokens(conf, job
      .getCredentials());
}

（2）真正的作业提交部分

[java] view plain copy print ?

@Override
public JobStatus submitJob(JobID jobId, String jobSubmitDir, Credentials ts)
throws IOException, InterruptedException {

  addHistoryToken(ts);

  // Construct necessary information to start the MR AM
  ApplicationSubmissionContext appContext =
    createApplicationSubmissionContext(conf, jobSubmitDir, ts);


  // Submit to ResourceManager
  try {
    ApplicationId applicationId =
        resMgrDelegate.submitApplication(appContext);


    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);
  }
}
原文链接：http://blog.csdn.net/lihm0_1/article/details/22186833