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例如，Floodlight openflow 堆栈使用 Netty 作为其 IO，它定义了以下 Pipeline 工厂类。

public class OpenflowPipelineFactory implements ChannelPipelineFactory {

    protected Controller controller;
    protected ThreadPoolExecutor pipelineExecutor;
    protected Timer timer;
    protected IdleStateHandler idleHandler;
    protected ReadTimeoutHandler readTimeoutHandler;

    public OpenflowPipelineFactory(Controller controller,
                                   ThreadPoolExecutor pipelineExecutor) {
        super();
        this.controller = controller;
        this.pipelineExecutor = pipelineExecutor;
        this.timer = new HashedWheelTimer();
        this.idleHandler = new IdleStateHandler(timer, 20, 25, 0);
        this.readTimeoutHandler = new ReadTimeoutHandler(timer, 30);
    }

    @Override
    public ChannelPipeline getPipeline() throws Exception {
        OFChannelState state = new OFChannelState();

        ChannelPipeline pipeline = Channels.pipeline();
        pipeline.addLast("ofmessagedecoder", new OFMessageDecoder());
        pipeline.addLast("ofmessageencoder", new OFMessageEncoder());
        pipeline.addLast("idle", idleHandler);
        pipeline.addLast("timeout", readTimeoutHandler);
        pipeline.addLast("handshaketimeout",
                         new HandshakeTimeoutHandler(state, timer, 15));
        if (pipelineExecutor != null)
            pipeline.addLast("pipelineExecutor",
                             new ExecutionHandler(pipelineExecutor));
        pipeline.addLast("handler", controller.getChannelHandler(state));
        return pipeline;
    }

}

但事实上，由于 Floodlight 将 null 赋予构造函数的第二个参数，执行处理程序和执行程序对象永远不会分配给管道。

...
final ServerBootstrap bootstrap = createServerBootStrap();

bootstrap.setOption("reuseAddr", true);
bootstrap.setOption("child.keepAlive", true);
bootstrap.setOption("child.tcpNoDelay", true);
bootstrap.setOption("child.sendBufferSize", Controller.SEND_BUFFER_SIZE);

ChannelPipelineFactory pfact = new OpenflowPipelineFactory(this, null);
bootstrap.setPipelineFactory(pfact);
InetSocketAddress sa = new InetSocketAddress(openFlowPort);
final ChannelGroup cg = new DefaultChannelGroup();
cg.add(bootstrap.bind(sa));
...

我的问题是，“如果没有为管道设置管道执行器会发生什么”？假设任何默认管道执行器？如果是，总是假定 OrderedMemoryAwareThreadPoolExecutor 执行器？

提前感谢您，等待 Netty 和 Floodlight 专家的帮助。

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1 回答 1

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如果 ChannelPipeline 中没有 ExecutionHandler，则所有事件都将由 IO 线程处理。如果添加了 ExecutionHandler，则事件将被卸载到 ExecutionHandler 之后的处理程序的额外线程池。这允许阻塞操作。

于 2013-03-29T06:33:37.143 回答