客户端发送tcp请求给服务端，最终所有服务端的逻辑都存在于服务端的netty中，进一步说就是channelHandler中

public class NettyServerPipelineFactory implements ChannelPipelineFactory {

    private NettyServer server;

    private static CodecConfig codecConfig = CodecConfigFactory.createClientConfig();

    public NettyServerPipelineFactory(NettyServer server) {
        this.server = server;
    }

    public ChannelPipeline getPipeline() {
        ChannelPipeline pipeline = pipeline();
        pipeline.addLast("framePrepender", new FramePrepender());
        pipeline.addLast("frameDecoder", new FrameDecoder());
        pipeline.addLast("crc32Handler", new Crc32Handler(codecConfig));
        pipeline.addLast("compressHandler", new CompressHandler(codecConfig));
        pipeline.addLast("providerDecoder", new ProviderDecoder());
        pipeline.addLast("providerEncoder", new ProviderEncoder());
        pipeline.addLast("serverHandler", new NettyServerHandler(server));
        return pipeline;
    }

}

　　经过解码，crc校验，解压缩，反序列化之后，最后到达 NettyServerHandler

 @Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent message) {
        CodecEvent codecEvent = (CodecEvent) (message.getMessage());

        if (!codecEvent.isValid() || codecEvent.getInvocation() == null) {
            return;
        }

        InvocationRequest request = (InvocationRequest) codecEvent.getInvocation();

        ProviderContext invocationContext = new DefaultProviderContext(request, new NettyServerChannel(ctx.getChannel()));
        try {
            this.server.processRequest(request, invocationContext);

        } catch (Throwable e) {
            String msg = "process request failed:" + request;
            // 心跳消息只返回正常的, 异常不返回
            if (request.getCallType() == Constants.CALLTYPE_REPLY
                    && request.getMessageType() != Constants.MESSAGE_TYPE_HEART) {
                ctx.getChannel().write(ProviderUtils.createFailResponse(request, e));
            }
            log.error(msg, e);
        }
    }

　　AbstractServer # processRequest

public Future<InvocationResponse> processRequest(InvocationRequest request, ProviderContext providerContext) {
        return requestProcessor.processRequest(request, providerContext);
    }

　　AbstractRequestProcessor # processRequest

public Future<InvocationResponse> processRequest(final InvocationRequest request,
            final ProviderContext providerContext) {
        if (request.getCreateMillisTime() == 0) {
            request.setCreateMillisTime(System.currentTimeMillis());
        }
        Future<InvocationResponse> invocationResponse = null;
        try {
            invocationResponse = doProcessRequest(request, providerContext);
        } catch (Throwable e) {
            String msg = "process request failed:" + request;
            if (request.getCallType() == Constants.CALLTYPE_REPLY
                    && request.getMessageType() != Constants.MESSAGE_TYPE_HEART) {
                providerContext.getChannel().write(providerContext, ProviderUtils.createFailResponse(request, e));
            }
            // logger.error(msg, e);
        }
        providerContext.setFuture(invocationResponse);
        return invocationResponse;
    }

RequestThreadPoolProcessor#doProcessRequest

public Future<InvocationResponse> doProcessRequest(final InvocationRequest request,
                                                       final ProviderContext providerContext) {
        requestContextMap.put(request, providerContext);

        startMonitorData(request, providerContext);

        Callable<InvocationResponse> requestExecutor = new Callable<InvocationResponse>() {

            @Override
            public InvocationResponse call() throws Exception {
                providerContext.getTimeline().add(new TimePoint(TimePhase.T));
                try {
                    ServiceInvocationHandler invocationHandler = ProviderProcessHandlerFactory
                            .selectInvocationHandler(providerContext.getRequest().getMessageType());
                    if (invocationHandler != null) {
                        providerContext.setThread(Thread.currentThread());
                        return invocationHandler.handle(providerContext);
                    }
                } catch (Throwable t) {
                    logger.error("Process request failed with invocation handler, you should never be here.", t);
                } finally {
                    requestContextMap.remove(request);
                }
                return null;
            }
        };
        final ThreadPool pool = selectThreadPool(request);//选择执行线程池部分 不关注，因为一般也不会设置都是用默认的

        try {
            checkRequest(pool, request);
            providerContext.getTimeline().add(new TimePoint(TimePhase.T));
            return pool.submit(requestExecutor);
        } catch (RejectedExecutionException e) {
            requestContextMap.remove(request);
            endMonitorData(request, providerContext);
            throw new RejectedException(getProcessorStatistics(pool), e);
        }

    }

如果不设置 就是 

public static final int DEFAULT_PROVIDER_COREPOOLSIZE = 60;//coresize

public static final int DEFAULT_PROVIDER_MAXPOOLSIZE = 500; // maxsize

重点看这段逻辑

ServiceInvocationHandler invocationHandler = ProviderProcessHandlerFactory
                            .selectInvocationHandler(providerContext.getRequest().getMessageType());
                    if (invocationHandler != null) {
                        providerContext.setThread(Thread.currentThread());
                        return invocationHandler.handle(providerContext);

又是熟悉的责任链模式，看来作者真的很擅长责任链