HADOOP源码分析之RPC（1）

源码位于Hadoop-common ipc包下

abstract class Server

构造Server

protected Server(String bindAddress, int port,
      Class<? extends Writable> rpcRequestClass, int handlerCount,
      int numReaders, int queueSizePerHandler, Configuration conf,
      String serverName, SecretManager<? extends TokenIdentifier> secretManager,
      String portRangeConfig)
    throws IOException {

    //监听地址
    this.bindAddress = bindAddress;
    this.conf = conf;
    this.portRangeConfig = portRangeConfig;
    //监听端口
    this.port = port;
    this.rpcRequestClass = rpcRequestClass; 
    //处理器个数
    this.handlerCount = handlerCount;
    this.socketSendBufferSize = 0;
    this.maxDataLength = conf.getInt(CommonConfigurationKeys.IPC_MAXIMUM_DATA_LENGTH,
        CommonConfigurationKeys.IPC_MAXIMUM_DATA_LENGTH_DEFAULT);
    if (queueSizePerHandler != -1) {
      this.maxQueueSize = handlerCount * queueSizePerHandler;
    } else {
      this.maxQueueSize = handlerCount * conf.getInt(
          CommonConfigurationKeys.IPC_SERVER_HANDLER_QUEUE_SIZE_KEY,
          CommonConfigurationKeys.IPC_SERVER_HANDLER_QUEUE_SIZE_DEFAULT);      
    }
    this.maxRespSize = conf.getInt(
        CommonConfigurationKeys.IPC_SERVER_RPC_MAX_RESPONSE_SIZE_KEY,
        CommonConfigurationKeys.IPC_SERVER_RPC_MAX_RESPONSE_SIZE_DEFAULT);
    if (numReaders != -1) {
      this.readThreads = numReaders;
    } else {
      this.readThreads = conf.getInt(
          CommonConfigurationKeys.IPC_SERVER_RPC_READ_THREADS_KEY,
          CommonConfigurationKeys.IPC_SERVER_RPC_READ_THREADS_DEFAULT);
    }
    this.readerPendingConnectionQueue = conf.getInt(
        CommonConfigurationKeys.IPC_SERVER_RPC_READ_CONNECTION_QUEUE_SIZE_KEY,
        CommonConfigurationKeys.IPC_SERVER_RPC_READ_CONNECTION_QUEUE_SIZE_DEFAULT);

    // Setup appropriate callqueue
    final String prefix = getQueueClassPrefix();
    this.callQueue = new CallQueueManager<Call>(getQueueClass(prefix, conf),
        getSchedulerClass(prefix, conf),
        getClientBackoffEnable(prefix, conf), maxQueueSize, prefix, conf);

    this.secretManager = (SecretManager<TokenIdentifier>) secretManager;
    this.authorize = 
      conf.getBoolean(CommonConfigurationKeys.HADOOP_SECURITY_AUTHORIZATION, 
                      false);

    // configure supported authentications
    this.enabledAuthMethods = getAuthMethods(secretManager, conf);
    this.negotiateResponse = buildNegotiateResponse(enabledAuthMethods);
    
    // Start the listener here and let it bind to the port
    //监听器
    listener = new Listener();
    this.port = listener.getAddress().getPort();    
    connectionManager = new ConnectionManager();
    this.rpcMetrics = RpcMetrics.create(this, conf);
    this.rpcDetailedMetrics = RpcDetailedMetrics.create(this.port);
    this.tcpNoDelay = conf.getBoolean(
        CommonConfigurationKeysPublic.IPC_SERVER_TCPNODELAY_KEY,
        CommonConfigurationKeysPublic.IPC_SERVER_TCPNODELAY_DEFAULT);

    this.setLogSlowRPC(conf.getBoolean(
        CommonConfigurationKeysPublic.IPC_SERVER_LOG_SLOW_RPC,
        CommonConfigurationKeysPublic.IPC_SERVER_LOG_SLOW_RPC_DEFAULT));

    // Create the responder here
    responder = new Responder();
    
    if (secretManager != null || UserGroupInformation.isSecurityEnabled()) {
      SaslRpcServer.init(conf);
      saslPropsResolver = SaslPropertiesResolver.getInstance(conf);
    }
    
    this.exceptionsHandler.addTerseLoggingExceptions(StandbyException.class);
  }

Server的主要组成即Listener、

均是单独的线程，底层利用Java NIO实现（Reactor设计模式）  参考NIO系列文章：http://ifeve.com/overview/

如下是创建Listener的源码：

　　　 //创建一个ServerSocketChannel 
      acceptChannel = ServerSocketChannel.open();
      acceptChannel.configureBlocking(false);

      // Bind the server socket to the local host and port
      bind(acceptChannel.socket(), address, backlogLength, conf, portRangeConfig);
      port = acceptChannel.socket().getLocalPort(); //Could be an ephemeral port
      // create a selector;
      selector= Selector.open();
      readers = new Reader[readThreads];
      for (int i = 0; i < readThreads; i++) {
        Reader reader = new Reader(
            "Socket Reader #" + (i + 1) + " for port " + port);
        readers[i] = reader;
        reader.start();
      }

      // Register accepts on the server socket with the selector.
      //注册channel到selector
　　　 acceptChannel.register(selector, SelectionKey.OP_ACCEPT);
      this.setName("IPC Server listener on " + port);
      this.setDaemon(true);
    

Listener线程通过Selector不断监听请求建立连接的Socket

public void run() {
      LOG.info(Thread.currentThread().getName() + ": starting");
      SERVER.set(Server.this);
      connectionManager.startIdleScan();
      while (running) {
        SelectionKey key = null;
        try {
          getSelector().select();
          Iterator<SelectionKey> iter = getSelector().selectedKeys().iterator();
          while (iter.hasNext()) {
            key = iter.next();
            iter.remove();
            try {
              if (key.isValid()) {
                if (key.isAcceptable())
                  doAccept(key);
              }
            } catch (IOException e) {
            }
            key = null;
          }
        } catch (OutOfMemoryError e) {
          // we can run out of memory if we have too many threads
          // log the event and sleep for a minute and give 
          // some thread(s) a chance to finish
          LOG.warn("Out of Memory in server select", e);
          closeCurrentConnection(key, e);
          connectionManager.closeIdle(true);
          try { Thread.sleep(60000); } catch (Exception ie) {}
        } catch (Exception e) {
          closeCurrentConnection(key, e);
        }
      }
      LOG.info("Stopping " + Thread.currentThread().getName());

      synchronized (this) {
        try {
          acceptChannel.close();
          selector.close();
        } catch (IOException e) { }

        selector= null;
        acceptChannel= null;
        
        // close all connections
        connectionManager.stopIdleScan();
        connectionManager.closeAll();
      }
    }