当我添加一个ExecutionHandler时，netty服务器似乎被阻塞了？

Question

THE SCENE：

我正在写回声客户端和服务器。被传输的数据是一个字符串：

客户端编码一个字符串，并将其发送到服务器。 服务器接收数据，解码字符串，然后对收到的字符串进行编码，并将其发送回客户端。

上述过程将重复100000次（注意：连接是持久的）。

输精管CONTIONS：

当我运行在同一时间一个服务器和两个客户端，一切都很好，每一个客户端接收10万点的消息，并正常终止。

但是当我添加服务器上ExecutionHandler，然后运行一台服务器，并在同一时间两个客户端，一个客户将永远不会终止，而网络流量为零。

现在我无法找到这个问题的关键点，你会给我一些建议吗？

我的代码：

串编码器，解码器的字符串，客户端的处理程序，服务器处理器，客户端主，主服务器。

//解码器=========================================== ============

import java.nio.charset.Charset; 

import org.jboss.netty.buffer.ChannelBuffer; 
import org.jboss.netty.channel.Channel; 
import org.jboss.netty.channel.ChannelHandlerContext; 
import org.jboss.netty.handler.codec.frame.FrameDecoder; 

public class Dcd extends FrameDecoder { 
    public static final Charset cs = Charset.forName("utf8"); 

    @Override 
    protected Object decode(ChannelHandlerContext ctx, Channel channel, 
      ChannelBuffer buffer) throws Exception { 

     if (buffer.readableBytes() < 4) { 
      return null; 
     } 

     int headlen = 4; 
     int length = buffer.getInt(0); 
     if (buffer.readableBytes() < length + headlen) { 
      return null; 
     } 

     String ret = buffer.toString(headlen, length, cs); 
     buffer.skipBytes(length + headlen); 

     return ret; 
    } 
} 

//编码器============================ ===========================

import org.jboss.netty.buffer.ChannelBuffer; 
import org.jboss.netty.buffer.ChannelBuffers; 
import org.jboss.netty.channel.Channel; 
import org.jboss.netty.channel.ChannelHandlerContext; 
import org.jboss.netty.handler.codec.oneone.OneToOneEncoder; 

public class Ecd extends OneToOneEncoder { 
    @Override 
    protected Object encode(ChannelHandlerContext ctx, Channel channel, 
      Object msg) throws Exception { 
     if (!(msg instanceof String)) { 
      return msg; 
     } 

     byte[] data = ((String) msg).getBytes(); 

     ChannelBuffer buf = ChannelBuffers.dynamicBuffer(data.length + 4, ctx 
       .getChannel().getConfig().getBufferFactory()); 
     buf.writeInt(data.length); 
     buf.writeBytes(data); 

     return buf; 
    } 
} 

//客户端处理程序============ ===========================================

import java.util.concurrent.atomic.AtomicInteger; 
import java.util.concurrent.atomic.AtomicLong; 
import java.util.logging.Level; 
import java.util.logging.Logger; 

import org.jboss.netty.channel.ChannelHandlerContext; 
import org.jboss.netty.channel.ChannelStateEvent; 
import org.jboss.netty.channel.Channels; 
import org.jboss.netty.channel.ExceptionEvent; 
import org.jboss.netty.channel.MessageEvent; 
import org.jboss.netty.channel.SimpleChannelUpstreamHandler; 

/** 
* Handler implementation for the echo client. It initiates the ping-pong 
* traffic between the echo client and server by sending the first message to 
* the server. 
*/ 
public class EchoClientHandler extends SimpleChannelUpstreamHandler { 

    private static final Logger logger = Logger 
      .getLogger(EchoClientHandler.class.getName()); 

    private final AtomicLong transferredBytes = new AtomicLong(); 
    private final AtomicInteger counter = new AtomicInteger(0); 
    private final AtomicLong startTime = new AtomicLong(0); 

    private String dd; 

    /** 
    * Creates a client-side handler. 
    */ 
    public EchoClientHandler(String data) { 
     dd = data; 
    } 

    public long getTransferredBytes() { 
     return transferredBytes.get(); 
    } 

    @Override 
    public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) { 
     // Send the first message. Server will not send anything here 
     // because the firstMessage's capacity is 0. 
     startTime.set(System.currentTimeMillis()); 

     Channels.write(ctx.getChannel(), dd); 
    } 

    @Override 
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) { 
     // Send back the received message to the remote peer. 
     transferredBytes.addAndGet(((String) e.getMessage()).length()); 
     int i = counter.incrementAndGet(); 
     int N = 100000; 
     if (i < N) { 
      e.getChannel().write(e.getMessage()); 
     } else { 
      ctx.getChannel().close(); 
      System.out.println(N * 1.0 
        /(System.currentTimeMillis() - startTime.get()) * 1000); 
     } 
    } 

    @Override 
    public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) { 
     // Close the connection when an exception is raised. 
     logger.log(Level.WARNING, "Unexpected exception from downstream.", 
       e.getCause()); 
     e.getChannel().close(); 
    } 
} 

//客户端主要===================== ==================================

import java.net.InetSocketAddress; 
import java.util.ArrayList; 
import java.util.List; 
import java.util.concurrent.Executors; 

import org.jboss.netty.bootstrap.ClientBootstrap; 
import org.jboss.netty.channel.ChannelFuture; 
import org.jboss.netty.channel.ChannelPipeline; 
import org.jboss.netty.channel.ChannelPipelineFactory; 
import org.jboss.netty.channel.Channels; 
import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory; 

/** 
* Sends one message when a connection is open and echoes back any received data 
* to the server. Simply put, the echo client initiates the ping-pong traffic 
* between the echo client and server by sending the first message to the 
* server. 
*/ 
public class EchoClient { 

    private final String host; 
    private final int port; 

    public EchoClient(String host, int port) { 
     this.host = host; 
     this.port = port; 
    } 

    public void run() { 
     // Configure the client. 
     final ClientBootstrap bootstrap = new ClientBootstrap(
       new NioClientSocketChannelFactory(
         Executors.newCachedThreadPool(), 
         Executors.newCachedThreadPool())); 

     // Set up the pipeline factory. 
     bootstrap.setPipelineFactory(new ChannelPipelineFactory() { 
      public ChannelPipeline getPipeline() throws Exception { 
       return Channels.pipeline(new Dcd(), new Ecd(), 
         new EchoClientHandler("abcdd")); 
      } 
     }); 

     bootstrap.setOption("sendBufferSize", 1048576); 
     bootstrap.setOption("receiveBufferSize", 1048576); 
     bootstrap.setOption("tcpNoDelay", true); 
     bootstrap.setOption("writeBufferLowWaterMark", 32 * 1024); 
     bootstrap.setOption("writeBufferHighWaterMark", 64 * 1024); 

     List<ChannelFuture> list = new ArrayList<ChannelFuture>(); 
     for (int i = 0; i < 1; i++) { 
      // Start the connection attempt. 
      ChannelFuture future = bootstrap.connect(new InetSocketAddress(
        host, port)); 
      // Wait until the connection is closed or the connection 
      // attempt 
      // fails. 
      list.add(future); 
     } 

     for (ChannelFuture f : list) { 
      f.getChannel().getCloseFuture().awaitUninterruptibly(); 
     } 

     // Shut down thread pools to exit. 
     bootstrap.releaseExternalResources(); 
    } 

    private static void testOne() { 
     final String host = "192.168.0.102"; 
     final int port = 8000; 

     new EchoClient(host, port).run(); 
    } 

    public static void main(String[] args) throws Exception { 
     testOne(); 
    } 
} 

//服务器处理程序===== ==================================================

import java.util.concurrent.atomic.AtomicLong; 
import java.util.logging.Level; 
import java.util.logging.Logger; 

import org.jboss.netty.channel.ChannelHandlerContext; 
import org.jboss.netty.channel.Channels; 
import org.jboss.netty.channel.ExceptionEvent; 
import org.jboss.netty.channel.MessageEvent; 
import org.jboss.netty.channel.SimpleChannelUpstreamHandler; 

/** 
* Handler implementation for the echo server. 
*/ 
public class EchoServerHandler extends SimpleChannelUpstreamHandler { 

    private static final Logger logger = Logger 
      .getLogger(EchoServerHandler.class.getName()); 

    private final AtomicLong transferredBytes = new AtomicLong(); 

    public long getTransferredBytes() { 
     return transferredBytes.get(); 
    } 

    @Override 
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) { 
     // Send back the received message to the remote peer. 
     transferredBytes.addAndGet(((String) e.getMessage()).length()); 
     Channels.write(ctx.getChannel(), e.getMessage()); 
    } 

    @Override 
    public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) { 
     // Close the connection when an exception is raised. 
     logger.log(Level.WARNING, "Unexpected exception from downstream.", 
       e.getCause()); 
     e.getChannel().close(); 
    } 
} 

// Server main ======================================= ================

import java.net.InetSocketAddress; 
import java.util.concurrent.Executors; 

import org.jboss.netty.bootstrap.ServerBootstrap; 
import org.jboss.netty.channel.ChannelPipeline; 
import org.jboss.netty.channel.ChannelPipelineFactory; 
import org.jboss.netty.channel.Channels; 
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory; 
import org.jboss.netty.handler.execution.ExecutionHandler; 
import org.jboss.netty.handler.execution.OrderedMemoryAwareThreadPoolExecutor; 

/** 
* Echoes back any received data from a client. 
*/ 
public class EchoServer { 

    private final int port; 

    public EchoServer(int port) { 
     this.port = port; 
    } 

    public void run() { 
     // Configure the server. 
     ServerBootstrap bootstrap = new ServerBootstrap(
       new NioServerSocketChannelFactory(
         Executors.newCachedThreadPool(), 
         Executors.newCachedThreadPool())); 

     System.out.println(Runtime.getRuntime().availableProcessors() * 2); 

     final ExecutionHandler executionHandler = new ExecutionHandler(
       new OrderedMemoryAwareThreadPoolExecutor(16, 1048576, 1048576)); 

     // Set up the pipeline factory. 
     bootstrap.setPipelineFactory(new ChannelPipelineFactory() { 
      public ChannelPipeline getPipeline() throws Exception { 
       System.out.println("new pipe"); 
       return Channels.pipeline(new Dcd(), new Ecd(), 
         executionHandler, new EchoServerHandler()); 
      } 
     }); 

     bootstrap.setOption("child.sendBufferSize", 1048576); 
     bootstrap.setOption("child.receiveBufferSize", 1048576); 
     bootstrap.setOption("child.tcpNoDelay", true); 
     bootstrap.setOption("child.writeBufferLowWaterMark", 32 * 1024); 
     bootstrap.setOption("child.writeBufferHighWaterMark", 64 * 1024); 

     // Bind and start to accept incoming connections. 
     bootstrap.bind(new InetSocketAddress(port)); 
    } 

    public static void main(String[] args) throws Exception { 
     int port = 8000; 
     new EchoServer(port).run(); 
    } 
} 

Answer 1

我已经找到了原因，现在，这是一个艰苦的工作，但充满乐趣。

当添加一个ExecutionHandler时，该消息将被封装到一个Runnable任务中，并且将在ChildExecutor中执行。关键点在于：当执行程序几乎退出时，可能会将任务添加到ChildExecutor中，然后ChildExecutor将会忽略它。

我添加了三行代码和一些注释，最终的代码如下所示，它现在可以工作了，我应该邮寄给作者吗？：

private final class ChildExecutor implements Executor, Runnable { 
    private final Queue<Runnable> tasks = QueueFactory 
      .createQueue(Runnable.class); 
    private final AtomicBoolean isRunning = new AtomicBoolean(); 

    public void execute(Runnable command) { 
     // TODO: What todo if the add return false ? 
     tasks.add(command); 

     if (!isRunning.get()) { 
      doUnorderedExecute(this); 
     } else { 
     } 
    } 

    public void run() { 
     // check if its already running by using CAS. If so just return 
     // here. So in the worst case the thread 
     // is executed and do nothing 
     boolean acquired = false; 
     if (isRunning.compareAndSet(false, true)) { 
      acquired = true; 
      try { 
       Thread thread = Thread.currentThread(); 
       for (;;) { 
        final Runnable task = tasks.poll(); 
        // if the task is null we should exit the loop 
        if (task == null) { 
         break; 
        } 

        boolean ran = false; 
        beforeExecute(thread, task); 
        try { 
         task.run(); 
         ran = true; 
         onAfterExecute(task, null); 
        } catch (RuntimeException e) { 
         if (!ran) { 
          onAfterExecute(task, e); 
         } 
         throw e; 
        } 
       } 
       //TODO NOTE (I added): between here and "isRunning.set(false)",some new tasks maybe added. 
      } finally { 
       // set it back to not running 
       isRunning.set(false); 
      } 
     } 

     //TODO NOTE (I added): Do the remaining works. 
     if (acquired && !isRunning.get() && tasks.peek() != null) { 
      doUnorderedExecute(this); 
     } 
    } 
} 

Answer 2

这是一个错误，将在3.4.0.Alpha2中修复。

见https://github.com/netty/netty/issues/234