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Hadoop2源码分析－YARN RPC 示例介绍详解大数据

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1.概述

　　之前在《Hadoop2源码分析－RPC探索实战》一文当中介绍了Hadoop的RPC机制，今天给大家分享关于YARN的RPC的机制。下面是今天的分享目录：

  • YARN的RPC介绍
  • YARN的RPC示例
  • 截图预览

　　下面开始今天的内容分享。

2.YARN的RPC介绍

　　我们知道在Hadoop的RPC当中，其主要由RPC，Client及Server这三个大类组成，分别实现对外提供编程接口、客户端实现及服务端实现。如下图所示：

Hadoop2源码分析－YARN RPC 示例介绍详解大数据

　　图中是Hadoop的RPC的一个类的关系图，大家可以到《Hadoop2源码分析－RPC探索实战》一文中，通过代码示例去理解他们之间的关系，这里就不多做赘述了。接下来，我们去看Yarn的RPC。

　　Yarn对外提供的是YarnRPC这个类，这是一个抽象类，通过阅读YarnRPC的源码可以知道，实际的实现由参数yarn.ipc.rpc.class设定，默认情况下，其值为：org.apache.hadoop.yarn.ipc.HadoopYarnProtoRPC，部分代码如下：

  • YarnRPC：
public abstract class YarnRPC { 
   // ...... 
 
    public static YarnRPC create(Configuration conf) { 
    LOG.debug("Creating YarnRPC for " +  
        conf.get(YarnConfiguration.IPC_RPC_IMPL)); 
    String clazzName = conf.get(YarnConfiguration.IPC_RPC_IMPL); 
    if (clazzName == null) { 
      clazzName = YarnConfiguration.DEFAULT_IPC_RPC_IMPL; 
    } 
    try { 
      return (YarnRPC) Class.forName(clazzName).newInstance(); 
    } catch (Exception e) { 
      throw new YarnRuntimeException(e); 
    } 
  } 
 
}
  • YarnConfiguration类：
public class YarnConfiguration extends Configuration { 
 
  //Configurations 
  public static final String YARN_PREFIX = "yarn."; 
 
  //////////////////////////////// 
  // IPC Configs 
  //////////////////////////////// 
  public static final String IPC_PREFIX = YARN_PREFIX + "ipc."; 
  /** RPC class implementation*/ 
  public static final String IPC_RPC_IMPL = 
    IPC_PREFIX + "rpc.class"; 
  public static final String DEFAULT_IPC_RPC_IMPL =  
    "org.apache.hadoop.yarn.ipc.HadoopYarnProtoRPC"; 
}

　　而HadoopYarnProtoRPC 通过 RPC 的 RpcFactoryProvider 生成客户端工厂(由参数 yarn.ipc.client.factory.class 指定，默认值是 org.apache.hadoop.yarn.factories.impl.pb.RpcClientFactoryPBImpl)和服务器工厂 (由参数 yarn.ipc.server.factory.class 指定，默认值是 org.apache.hadoop.yarn.factories.impl.pb.RpcServerFactoryPBImpl)，以根据通信协议的 Protocol Buffers 定义生成客户端对象和服务器对象。相关类的部分代码如下：

  • HadoopYarnProtoRPC
public class HadoopYarnProtoRPC extends YarnRPC { 
 
  private static final Log LOG = LogFactory.getLog(HadoopYarnProtoRPC.class); 
 
  @Override 
  public Object getProxy(Class protocol, InetSocketAddress addr, 
      Configuration conf) { 
    LOG.debug("Creating a HadoopYarnProtoRpc proxy for protocol " + protocol); 
    return RpcFactoryProvider.getClientFactory(conf).getClient(protocol, 1, 
        addr, conf); 
  } 
 
  @Override 
  public void stopProxy(Object proxy, Configuration conf) { 
    RpcFactoryProvider.getClientFactory(conf).stopClient(proxy); 
  } 
 
  @Override 
  public Server getServer(Class protocol, Object instance, 
      InetSocketAddress addr, Configuration conf, 
      SecretManager<? extends TokenIdentifier> secretManager, 
      int numHandlers, String portRangeConfig) { 
    LOG.debug("Creating a HadoopYarnProtoRpc server for protocol " + protocol +  
        " with " + numHandlers + " handlers"); 
     
    return RpcFactoryProvider.getServerFactory(conf).getServer(protocol,  
        instance, addr, conf, secretManager, numHandlers, portRangeConfig); 
 
  } 
 
}

  • RpcFactoryProvider

public class RpcFactoryProvider { 
 
  // ...... 
 
  public static RpcClientFactory getClientFactory(Configuration conf) { 
    String clientFactoryClassName = conf.get( 
        YarnConfiguration.IPC_CLIENT_FACTORY_CLASS, 
        YarnConfiguration.DEFAULT_IPC_CLIENT_FACTORY_CLASS); 
    return (RpcClientFactory) getFactoryClassInstance(clientFactoryClassName); 
  } 
 
  //...... 
   
}
/** Factory to create client IPC classes.*/ 
  public static final String IPC_CLIENT_FACTORY_CLASS = 
    IPC_PREFIX + "client.factory.class"; 
  public static final String DEFAULT_IPC_CLIENT_FACTORY_CLASS =  
      "org.apache.hadoop.yarn.factories.impl.pb.RpcClientFactoryPBImpl";

　　在 YARN 中并未使用Hadoop自带的Writable来做序列化，而是使用 Protocol Buffers 作为默认的序列化机制，这带来的好处主要有以下几点：

  • 继承Protocol Buffers的优点：Protocol Buffers已被实践证明其拥有高效性、可扩展性、紧凑性以及跨语言性等特点。
  • 支持在线升级回滚：在Hadoop 2.x版本后，添加的HA方案，该方案能够进行主备切换，在不停止NNA节点服务的前提下，能够在线升级版本。

3.YARN的RPC示例

　　YARN 的工作流程是先定义通信协议接口ResourceTracker，它包含2个函数，具体代码如下所示：

  • ResourceTracker：
public interface ResourceTracker { 
   
  @Idempotent 
  public RegisterNodeManagerResponse registerNodeManager( 
      RegisterNodeManagerRequest request) throws YarnException, 
      IOException; 
 
  @AtMostOnce 
  public NodeHeartbeatResponse nodeHeartbeat(NodeHeartbeatRequest request) 
      throws YarnException, IOException; 
 
}

　　这里ResourceTracker提供了Protocol Buffers定义和Java实现，其中设计的Protocol Buffers文件有：ResourceTracker.proto、yarn_server_common_service_protos.proto和yarn_server_common_protos.proto，文件路径在Hadoop的源码包的 hadoop-2.6.0-src/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/proto，这里就不贴出3个文件的具体代码类，大家可以到该目录去阅读这部分代码。这里需要注意的是，若是大家要编译这些文件需要安装 ProtoBuf 的编译环境，环境安装较为简单，这里给大家简要说明下。

　　首先是下载ProtoBuf的安装包，然后解压，进入到解压目录，编译安装。命令如下：

./configure --prefix=/home/work /protobuf/   
 
make && make install

最后编译 .proto 文件的命令：

protoc ./ResourceTracker.proto  --java_out=./

　　下面，我们去收取Hadoop源码到本地工程，运行调试相关代码。

  • TestYarnServerApiClasses：

public class TestYarnServerApiClasses { 
 
  // ...... 
 
  // 列举测试4个方法   
 
@Test 
  public void testRegisterNodeManagerResponsePBImpl() { 
    RegisterNodeManagerResponsePBImpl original = 
        new RegisterNodeManagerResponsePBImpl(); 
    original.setContainerTokenMasterKey(getMasterKey()); 
    original.setNMTokenMasterKey(getMasterKey()); 
    original.setNodeAction(NodeAction.NORMAL); 
    original.setDiagnosticsMessage("testDiagnosticMessage"); 
 
    RegisterNodeManagerResponsePBImpl copy = 
        new RegisterNodeManagerResponsePBImpl( 
            original.getProto()); 
    assertEquals(1, copy.getContainerTokenMasterKey().getKeyId()); 
    assertEquals(1, copy.getNMTokenMasterKey().getKeyId()); 
    assertEquals(NodeAction.NORMAL, copy.getNodeAction()); 
    assertEquals("testDiagnosticMessage", copy.getDiagnosticsMessage()); 
 
  } 
 
@Test 
  public void testNodeHeartbeatRequestPBImpl() { 
    NodeHeartbeatRequestPBImpl original = new NodeHeartbeatRequestPBImpl(); 
    original.setLastKnownContainerTokenMasterKey(getMasterKey()); 
    original.setLastKnownNMTokenMasterKey(getMasterKey()); 
    original.setNodeStatus(getNodeStatus()); 
    NodeHeartbeatRequestPBImpl copy = new NodeHeartbeatRequestPBImpl( 
        original.getProto()); 
    assertEquals(1, copy.getLastKnownContainerTokenMasterKey().getKeyId()); 
    assertEquals(1, copy.getLastKnownNMTokenMasterKey().getKeyId()); 
    assertEquals("localhost", copy.getNodeStatus().getNodeId().getHost()); 
  } 
 
@Test 
  public void testNodeHeartbeatResponsePBImpl() { 
    NodeHeartbeatResponsePBImpl original = new NodeHeartbeatResponsePBImpl(); 
 
    original.setDiagnosticsMessage("testDiagnosticMessage"); 
    original.setContainerTokenMasterKey(getMasterKey()); 
    original.setNMTokenMasterKey(getMasterKey()); 
    original.setNextHeartBeatInterval(1000); 
    original.setNodeAction(NodeAction.NORMAL); 
    original.setResponseId(100); 
 
    NodeHeartbeatResponsePBImpl copy = new NodeHeartbeatResponsePBImpl( 
        original.getProto()); 
    assertEquals(100, copy.getResponseId()); 
    assertEquals(NodeAction.NORMAL, copy.getNodeAction()); 
    assertEquals(1000, copy.getNextHeartBeatInterval()); 
    assertEquals(1, copy.getContainerTokenMasterKey().getKeyId()); 
    assertEquals(1, copy.getNMTokenMasterKey().getKeyId()); 
    assertEquals("testDiagnosticMessage", copy.getDiagnosticsMessage()); 
  } 
 
@Test 
  public void testRegisterNodeManagerRequestPBImpl() { 
    RegisterNodeManagerRequestPBImpl original = new RegisterNodeManagerRequestPBImpl(); 
    original.setHttpPort(8080); 
    original.setNodeId(getNodeId()); 
    Resource resource = recordFactory.newRecordInstance(Resource.class); 
    resource.setMemory(10000); 
    resource.setVirtualCores(2); 
    original.setResource(resource); 
    RegisterNodeManagerRequestPBImpl copy = new RegisterNodeManagerRequestPBImpl( 
        original.getProto()); 
 
    assertEquals(8080, copy.getHttpPort()); 
    assertEquals(9090, copy.getNodeId().getPort()); 
    assertEquals(10000, copy.getResource().getMemory()); 
    assertEquals(2, copy.getResource().getVirtualCores()); 
 
  } 
 
}

  • TestResourceTrackerPBClientImpl：

public class TestResourceTrackerPBClientImpl { 
 
    private static ResourceTracker client; 
    private static Server server; 
    private final static org.apache.hadoop.yarn.factories.RecordFactory recordFactory = RecordFactoryProvider 
            .getRecordFactory(null); 
 
    @BeforeClass 
    public static void start() { 
 
        System.out.println("Start client test"); 
 
        InetSocketAddress address = new InetSocketAddress(0); 
        Configuration configuration = new Configuration(); 
        ResourceTracker instance = new ResourceTrackerTestImpl(); 
        server = RpcServerFactoryPBImpl.get().getServer(ResourceTracker.class, instance, address, configuration, null, 
                1); 
        server.start(); 
 
        client = (ResourceTracker) RpcClientFactoryPBImpl.get().getClient(ResourceTracker.class, 1, 
                NetUtils.getConnectAddress(server), configuration); 
 
    } 
 
    @AfterClass 
    public static void stop() { 
 
        System.out.println("Stop client"); 
 
        if (server != null) { 
            server.stop(); 
        } 
    } 
 
    /** 
     * Test the method registerNodeManager. Method should return a not null 
     * result. 
     *  
     */ 
    @Test 
    public void testResourceTrackerPBClientImpl() throws Exception { 
        RegisterNodeManagerRequest request = recordFactory.newRecordInstance(RegisterNodeManagerRequest.class); 
        assertNotNull(client.registerNodeManager(request)); 
 
        ResourceTrackerTestImpl.exception = true; 
        try { 
            client.registerNodeManager(request); 
            fail("there should be YarnException"); 
        } catch (YarnException e) { 
            assertTrue(e.getMessage().startsWith("testMessage")); 
        } finally { 
            ResourceTrackerTestImpl.exception = false; 
        } 
 
    } 
 
    /** 
     * Test the method nodeHeartbeat. Method should return a not null result. 
     *  
     */ 
 
    @Test 
    public void testNodeHeartbeat() throws Exception { 
        NodeHeartbeatRequest request = recordFactory.newRecordInstance(NodeHeartbeatRequest.class); 
        assertNotNull(client.nodeHeartbeat(request)); 
 
        ResourceTrackerTestImpl.exception = true; 
        try { 
            client.nodeHeartbeat(request); 
            fail("there  should be YarnException"); 
        } catch (YarnException e) { 
            assertTrue(e.getMessage().startsWith("testMessage")); 
        } finally { 
            ResourceTrackerTestImpl.exception = false; 
        } 
 
    } 
 
    public static class ResourceTrackerTestImpl implements ResourceTracker { 
 
        public static boolean exception = false; 
 
        public RegisterNodeManagerResponse registerNodeManager(RegisterNodeManagerRequest request) 
                throws YarnException, IOException { 
            if (exception) { 
                throw new YarnException("testMessage"); 
            } 
            return recordFactory.newRecordInstance(RegisterNodeManagerResponse.class); 
        } 
 
        public NodeHeartbeatResponse nodeHeartbeat(NodeHeartbeatRequest request) throws YarnException, IOException { 
            if (exception) { 
                throw new YarnException("testMessage"); 
            } 
            return recordFactory.newRecordInstance(NodeHeartbeatResponse.class); 
        } 
 
    } 
}

4.截图预览

　　接下来，我们使用JUnit去测试代码，截图预览如下所示：

  • 对testRegisterNodeManagerRequestPBImpl()方法的一个DEBUG调试

Hadoop2源码分析－YARN RPC 示例介绍详解大数据

  • testResourceTrackerPBClientImpl()方法的DEBUG调试

Hadoop2源码分析－YARN RPC 示例介绍详解大数据

　　这里由于设置exception的状态为true，在调用registerNodeManager()时，会打印一条测试异常信息。

if (exception) { 
　　throw new YarnException("testMessage"); 
}

5.总结

　　在学习Hadoop YARN的RPC时，可以先了解Hadoop的RPC机制，这样在接触YARN的RPC的会比较好理解，YARN的RPC只是其中的一部分，后续会给大家分享更多关于YARN的内容。

6.结束语

　　这篇博客就和大家分享到这里，如果大家在研究学习的过程当中有什么问题，可以加群进行讨论或发送邮件给我，我会尽我所能为您解答，与君共勉！

原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/tech/bigdata/9919.html

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