Thrift源代码分析（七）-- TServerserver分析

Thrift採用了TServer来作为server的抽象，提供了多种类型的server实现。用TServerTransport作为server的Acceptor抽象，来监听端口。创建clientSocket连接

先来看看TServerTransport。主要有两类

1. TNonblockingServerTransport和TNonblockingServerSocket作为非堵塞IO的Acceptor,封装了ServerSocketChannel

2. TServerSocket作为堵塞同步IO的Acceptor，封装了ServerSocket

public class TNonblockingServerSocket extends TNonblockingServerTransport {
  private ServerSocketChannel serverSocketChannel = null;
}
 protected TNonblockingSocket acceptImpl() throws TTransportException {
    if (serverSocket_ == null) {
      throw new TTransportException(TTransportException.NOT_OPEN, "No underlying server socket.");
    }
    try {
      SocketChannel socketChannel = serverSocketChannel.accept();
      if (socketChannel == null) {
        return null;
      }

      TNonblockingSocket tsocket = new TNonblockingSocket(socketChannel);
      tsocket.setTimeout(clientTimeout_);
      return tsocket;
    } catch (IOException iox) {
      throw new TTransportException(iox);
    }
  }

  public void registerSelector(Selector selector) {
    try {
      // Register the server socket channel, indicating an interest in
      // accepting new connections
      serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
    } catch (ClosedChannelException e) {
      // this shouldn't happen, ideally...
      // TODO: decide what to do with this.
    }
  }
public class TServerSocket extends TServerTransport {
  private ServerSocket serverSocket_ = null;
}
 protected TSocket acceptImpl() throws TTransportException {
    if (serverSocket_ == null) {
      throw new TTransportException(TTransportException.NOT_OPEN, "No underlying server socket.");
    }
    try {
      Socket result = serverSocket_.accept();
      TSocket result2 = new TSocket(result);
      result2.setTimeout(clientTimeout_);
      return result2;
    } catch (IOException iox) {
      throw new TTransportException(iox);
    }
  }

再看TServer的类层次结构。主要也是两类，非堵塞IO和同步IO

非堵塞IO的Server有：

1. TNonblockingServer是单线程的，仅仅有一个SelectAcceptThread线程来轮询IO就绪事件，调用就绪的channel来对应Accept, Read, Write事件。而且还是使用这个线程来同步调用实际的方法实现。

2. THsHaServer是所谓的半同步半异步的server。所谓半同步是说使用一个SelectAcceptThread线程来轮询IO就绪事件，调用就绪的channel来对应Accept, Read, Write事件。所谓的半异步是说方法的调用是封装成一个Runnable交给线程池来运行的，交给线程池立马返回，不同步等待方法运行完成，方法运行完成的写返回是有线程池中的线程来做的，实现了所谓的异步訪问的模式。

3. TThreadSelectorServer，这个server类比較有意思。是多线程Reactor模式的一种实现。

3.1 採用了一个AcceptorThread来专门监听port，处理Accept事件，然后创建SocketChannel。创建完毕之后交给一个线程池来处理兴许动作，将SocketChannel放到SelecotrThread的堵塞队列acceptedQueue中

3.2 採用多个SelectorThread来处理创建好的SocketChannel。每一个SelectorThread绑定一个Selector。这样将SocketChannel分给多个Selector。

同一时候SelectorThread又维护了一个堵塞队列acceptedQueue，从acceptedQueue中拿新创建好的SocketChannel，来注冊读事件



同步的TServer有TThreadPoolServer，关联一个TServerSocket，採用同步IO的方式来Accept，然后交给一个线程池来处理兴许动作

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这里有一篇老外写的文章比較各种server的性能。https://github.com/m1ch1/mapkeeper/wiki/Thrift-Java-Servers-Compared

结论是TThreadSelectorServer在吞吐量和server响应时间的表现都是最优的