谈谈如何使用Netty开发实现高性能的RPC服务器

   <p>RPC（Remote Procedure Call Protocol）远程过程调用协议，它是一种通过网络，从远程计算机程序上请求服务，而不必了解底层网络技术的协议。说的再直白一点，就是客户端在不必知道调用细节的前提之下，调用远程计算机上运行的某个对象，使用起来就像调用本地的对象一样。目前典型的RPC实现框架有：Thrift（非死book开源）、Dubbo（alibaba开源）等等。RPC框架针对网络协议、网络I/O模型的封装是透明的，对于调用的客户端而言，它就认为自己在调用本地的一个对象。至于传输层上，运用的是TCP协议、UDP协议、亦或是HTTP协议，一概不关心。从网络I/O模型上来看，是基于select、poll、epoll方式、还是IOCP（I/O Completion Port）方式承载实现的，对于调用者而言也不用关心。</p>    <p>目前，主流的RPC框架都支持跨语言调用，即有所谓的IDL（接口定义语言），其实，这个并不是RPC所必须要求的。如果你的RPC框架没有跨语言的要求，IDL就可以不用包括了。</p>    <p>最后，值得一提的是，衡量一个RPC框架性能的好坏与否，RPC的网络I/O模型的选择，至关重要。在此基础上，设计出来的RPC服务器，可以考虑支持阻塞式同步IO、非阻塞式同步IO、当然还有所谓的多路复用IO模型、异步IO模型。支持不同的网络IO模型，在高并发的状态下，处理性能上会有很大的差别。还有一个衡量的标准，就是选择的传输协议。是基于TCP协议、还是HTTP协议、还是UDP协议？对性能也有一定的影响。但是从我目前了解的情况来看，大多数RPC开源实现框架都是基于TCP、或者HTTP的，目测没有采用UDP协议做为主要的传输协议的。</p>    <p>明白了RPC的使用原理和性能要求。现在，我们能不能撇开那些RPC开源框架，自己动手开发一个高性能的RPC服务器呢？我想，还是可以的。现在本人就使用Java，基于Netty，开发实现一个高性能的RPC服务器。</p>    <p>如何实现、基于什么原理？并发处理性能如何？请继续接着看下文。</p>    <p>我们有的时候，为了提高单个节点的通信吞吐量，提高通信性能。如果是基于Java后端的，一般首选的是NIO框架（No-block IO）。但是问题也来了，Java的NIO掌握起来要相当的技术功底，和足够的技术积累，使用起来才能得心应手。一般的开发人员，如果要使用NIO开发一个后端的TCP/HTTP服务器，附带考虑TCP粘包、网络通信异常、消息链接处理等等网络通信细节，开发门槛太高，所以比较明智的选择是，采用业界主流的NIO框架进行服务器后端开发。主流的NIO框架主要有Netty、Mina。它们主要都是基于TCP通信，非阻塞的IO、灵活的IO线程池而设计的，应对高并发请求也是绰绰有余。随着Netty、Mina这样优秀的NIO框架，设计上日趋完善，Java后端高性能服务器开发，在技术上提供了有力的支持保障，从而打破了C++在服务器后端，一统天下的局面。因为在此之前，Java的NIO一直受人诟病，让人敬而远之！</p>    <p>既然，这个RPC服务器是基于Netty的，那就在说说Netty吧。实际上Netty是对JAVA NIO框架的再次封装，它的开源网址是 <a href="/misc/goto?guid=4958545040601117512" rel="nofollow,noindex">http://netty.io/</a> ，本文中使用的Netty版本是：4.0版本，可以通过 <a href="/misc/goto?guid=4959675257500417264" rel="nofollow,noindex">http://dl.bintray.com/netty/downloads/netty-4.0.37.Final.tar.bz2</a> ，进行下载使用。那也许你会问，如何使用Netty进行RPC服务器的开发呢？实际不难，下面我就简单的说明一下技术原理：</p>    <p>1、定义RPC请求消息、应答消息结构，里面要包括RPC的接口定义模块、包括远程调用的类名、方法名称、参数结构、参数值等信息。</p>    <p>2、服务端初始化的时候通过容器加载RPC接口定义和RPC接口实现类对象的映射关系，然后等待客户端发起调用请求。</p>    <p>3、客户端发起的RPC消息里面包含，远程调用的类名、方法名称、参数结构、参数值等信息，通过网络，以字节流的方式送给RPC服务端，RPC服务端接收到字节流的请求之后，去对应的容器里面，查找客户端接口映射的具体实现对象。</p>    <p>4、RPC服务端找到实现对象的参数信息，通过反射机制创建该对象的实例，并返回调用处理结果，最后封装成RPC应答消息通知到客户端。</p>    <p>5、客户端通过网络，收到字节流形式的RPC应答消息，进行拆包、解析之后，显示远程调用结果。</p>    <p>上面说的是很简单，但是实现的时候，我们还要考虑如下的问题：</p>    <p>1、RPC服务器的传输层是基于TCP协议的，出现粘包咋办？这样客户端的请求，服务端不是会解析失败？好在Netty里面已经提供了解决TCP粘包问题的解码器：LengthFieldBasedFrameDecoder，可以靠它轻松搞定TCP粘包问题。</p>    <p>2、Netty服务端的线程模型是单线程、多线程（一个线程负责客户端连接，连接成功之后，丢给后端IO的线程池处理）、还是主从模式（客户端连接、后端IO处理都是基于线程池的实现）。当然在这里，我出于性能考虑，使用了Netty主从线程池模型。</p>    <p>3、Netty的IO处理线程池，如果遇到非常耗时的业务，出现阻塞了咋办？这样不是很容易把后端的NIO线程给挂死、阻塞？本文的处理方式是，对于复杂的后端业务，分派到专门的业务线程池里面，进行异步回调处理。</p>    <p>4、RPC消息的传输是通过字节流在NIO的通道（Channel）之间传输，那具体如何实现呢？本文，是通过基于Java原生对象序列化机制的编码、解码器（ObjectEncoder、ObjectDecoder）进行实现的。当然出于性能考虑，这个可能不是最优的方案。更优的方案是把消息的编码、解码器，搞成可以配置实现的。具体比如可以通过：protobuf、JBoss Marshalling方式进行解码和编码，以提高网络消息的传输效率。</p>    <p>5、RPC服务器要考虑多线程、高并发的使用场景，所以线程安全是必须的。此外尽量不要使用synchronized进行加锁，改用轻量级的ReentrantLock方式进行代码块的条件加锁。比如本文中的RPC消息处理回调，就有这方面的使用。</p>    <p>6、RPC服务端的服务接口对象和服务接口实现对象要能轻易的配置，轻松进行加载、卸载。在这里，本文是通过Spring容器进行统一的对象管理。</p>    <p>综上所述，本文设计的RPC服务器调用的流程图如下所示：</p>    <p><img src="https://simg.open-open.com/show/7901f810dbe26a454017d9457dc3d461.jpg"></p>    <p>客户端并发发起RPC调用请求，然后RPC服务端使用Netty连接器，分派出N个NIO连接线程，这个时候Netty连接器的任务结束。然后NIO连接线程是统一放到Netty NIO处理线程池进行管理，这个线程池里面会对具体的RPC请求连接进行消息编码、消息解码、消息处理等等一系列操作。最后进行消息处理（Handler）的时候，处于性能考虑，这里的设计是，直接把复杂的消息处理过程，丢给专门的RPC业务处理线程池集中处理，然后Handler对应的NIO线程就立即返回、不会阻塞。这个时候RPC调用结束，客户端会异步等待服务端消息的处理结果，本文是通过消息回调机制实现（MessageCallBack）。</p>    <p>再来说一说Netty对于RPC消息的解码、编码、处理对应的模块和流程，具体如下图所示：</p>    <p><img src="https://simg.open-open.com/show/1e5a1fdc793ad77aa9637e140e6dbecf.jpg"></p>    <p>从上图可以看出客户端、服务端对RPC消息编码、解码、处理调用的模块以及调用顺序了。Netty就是把这样一个一个的处理器串在一起，形成一个责任链，统一进行调用。</p>    <p>说了这么多，现在先简单看下，我设计实现的NettyRPC的代码目录层级结构：</p>    <p><img src="https://simg.open-open.com/show/c5b470d52d6dda72d48026a8e1daa4a9.jpg"></p>    <p>其中newlandframework.netty.rpc.core包是NettyRPC的核心实现。newlandframework.netty.rpc.model包里面，则封装了RPC消息请求、应答报文结构，以及RPC服务接口与实现绑定关系的容器定义。newlandframework.netty.rpc.config里面定义了NettyRPC的服务端文件配置属性。</p>    <p>下面先来看下newlandframework.netty.rpc.model包中定义的内容。具体是RPC消息请求、应答消息的结构定义：</p>    <p>RPC请求消息结构</p>    <pre>  <code class="language-java">/**   * @filename:MessageRequest.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:rpc服务请求结构   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.model;    import java.io.Serializable;  import org.apache.commons.lang.builder.ToStringBuilder;  import org.apache.commons.lang.builder.ToStringStyle;    public class MessageRequest implements Serializable {        private String messageId;      private String className;      private String methodName;      private Class<?>[] typeParameters;      private Object[] parametersVal;        public String getMessageId() {          return messageId;      }        public void setMessageId(String messageId) {          this.messageId = messageId;      }        public String getClassName() {          return className;      }        public void setClassName(String className) {          this.className = className;      }        public String getMethodName() {          return methodName;      }        public void setMethodName(String methodName) {          this.methodName = methodName;      }        public Class<?>[] gettypeParameters() {          return typeParameters;      }        public void settypeParameters(Class<?>[] typeParameters) {          this.typeParameters = typeParameters;      }        public Object[] getParameters() {          return parametersVal;      }        public void setParameters(Object[] parametersVal) {          this.parametersVal = parametersVal;      }        public String toString() {          return new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE)                  .append("messageId", messageId).append("className", className)                  .append("methodName", methodName).toString();      }  }  </code></pre>    <p>RPC应答消息结构</p>    <pre>  <code class="language-java">/**   * @filename:MessageResponse.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:rpc服务应答结构   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.model;    import java.io.Serializable;  import org.apache.commons.lang.builder.ToStringBuilder;  import org.apache.commons.lang.builder.ToStringStyle;    public class MessageResponse implements Serializable {        private String messageId;      private String error;      private Object resultDesc;        public String getMessageId() {          return messageId;      }        public void setMessageId(String messageId) {          this.messageId = messageId;      }        public String getError() {          return error;      }        public void setError(String error) {          this.error = error;      }        public Object getResult() {          return resultDesc;      }        public void setResult(Object resultDesc) {          this.resultDesc = resultDesc;      }        public String toString() {          return new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE)                  .append("messageId", messageId).append("error", error).toString();      }  }  </code></pre>    <p>RPC服务接口定义、服务接口实现绑定关系容器定义，提供给spring作为容器使用。</p>    <pre>  <code class="language-java">/**   * @filename:MessageKeyVal.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:rpc服务映射容器   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.model;    import java.util.Map;    public class MessageKeyVal {        private Map<String, Object> messageKeyVal;        public void setMessageKeyVal(Map<String, Object> messageKeyVal) {          this.messageKeyVal = messageKeyVal;      }        public Map<String, Object> getMessageKeyVal() {          return messageKeyVal;      }  }  </code></pre>    <p>好了，定义好核心模型结构之后，现在再向大家展示一下NettyRPC核心包：newlandframework.netty.rpc.core的关键部分实现代码，首先是业务线程池相关类的实现代码，具体如下：</p>    <p>线程工厂定义实现</p>    <pre>  <code class="language-java">/**   * @filename:NamedThreadFactory.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:线程工厂   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import java.util.concurrent.ThreadFactory;  import java.util.concurrent.atomic.AtomicInteger;    public class NamedThreadFactory implements ThreadFactory {        private static final AtomicInteger threadNumber = new AtomicInteger(1);        private final AtomicInteger mThreadNum = new AtomicInteger(1);        private final String prefix;        private final boolean daemoThread;        private final ThreadGroup threadGroup;        public NamedThreadFactory() {          this("rpcserver-threadpool-" + threadNumber.getAndIncrement(), false);      }        public NamedThreadFactory(String prefix) {          this(prefix, false);      }        public NamedThreadFactory(String prefix, boolean daemo) {          this.prefix = prefix + "-thread-";          daemoThread = daemo;          SecurityManager s = System.getSecurityManager();          threadGroup = (s == null) ? Thread.currentThread().getThreadGroup() : s.getThreadGroup();      }        public Thread newThread(Runnable runnable) {          String name = prefix + mThreadNum.getAndIncrement();          Thread ret = new Thread(threadGroup, runnable, name, 0);          ret.setDaemon(daemoThread);          return ret;      }        public ThreadGroup getThreadGroup() {          return threadGroup;      }  }  </code></pre>    <p>业务线程池定义实现</p>    <pre>  <code class="language-java">/**   * @filename:RpcThreadPool.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:rpc线程池封装   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import java.util.concurrent.Executor;  import java.util.concurrent.LinkedBlockingQueue;  import java.util.concurrent.SynchronousQueue;  import java.util.concurrent.ThreadPoolExecutor;  import java.util.concurrent.TimeUnit;    public class RpcThreadPool {        //独立出线程池主要是为了应对复杂耗I/O操作的业务，不阻塞netty的handler线程而引入      //当然如果业务足够简单，把处理逻辑写入netty的handler（ChannelInboundHandlerAdapter）也未尝不可      public static Executor getExecutor(int threads, int queues) {          String name = "RpcThreadPool";          return new ThreadPoolExecutor(threads, threads, 0, TimeUnit.MILLISECONDS,                  queues == 0 ? new SynchronousQueue<Runnable>()                          : (queues < 0 ? new LinkedBlockingQueue<Runnable>()                                  : new LinkedBlockingQueue<Runnable>(queues)),                  new NamedThreadFactory(name, true), new AbortPolicyWithReport(name));      }  }  </code></pre>    <pre>  <code class="language-java">/**   * @filename:AbortPolicyWithReport.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:线程池异常策略   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import java.util.concurrent.RejectedExecutionException;  import java.util.concurrent.ThreadPoolExecutor;    public class AbortPolicyWithReport extends ThreadPoolExecutor.AbortPolicy {        private final String threadName;        public AbortPolicyWithReport(String threadName) {          this.threadName = threadName;      }        public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {          String msg = String.format("RpcServer["                  + " Thread Name: %s, Pool Size: %d (active: %d, core: %d, max: %d, largest: %d), Task: %d (completed: %d),"                  + " Executor status:(isShutdown:%s, isTerminated:%s, isTerminating:%s)]",                  threadName, e.getPoolSize(), e.getActiveCount(), e.getCorePoolSize(), e.getMaximumPoolSize(), e.getLargestPoolSize(),                  e.getTaskCount(), e.getCompletedTaskCount(), e.isShutdown(), e.isTerminated(), e.isTerminating());          System.out.println(msg);          throw new RejectedExecutionException(msg);      }  }  </code></pre>    <p>RPC调用客户端定义实现</p>    <pre>  <code class="language-java">/**   * @filename:MessageSendExecutor.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:Rpc客户端执行模块   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import java.lang.reflect.Proxy;    public class MessageSendExecutor {        private RpcServerLoader loader = RpcServerLoader.getInstance();        public MessageSendExecutor(String serverAddress) {          loader.load(serverAddress);      }        public void stop() {          loader.unLoad();      }        public static <T> T execute(Class<T> rpcInterface) {          return (T) Proxy.newProxyInstance(                  rpcInterface.getClassLoader(),                  new Class<?>[]{rpcInterface},                  new MessageSendProxy<T>(rpcInterface)          );      }  }  </code></pre>    <p>这里的RPC客户端实际上，是动态代理了MessageSendProxy，当然这里是应用了，JDK原生的动态代理实现，你还可以改成CGLIB（Code Generation Library）方式。不过本人测试了一下CGLIB方式，在高并发的情况下面会出现空指针异常，但是同样的情况，JDK原生的动态代理却没有问题。并发程度不高的情况下面，两种代理方式都运行正常。后续再深入研究看看吧！废话不说了，现在给出MessageSendProxy的实现方式</p>    <pre>  <code class="language-java">/**   * @filename:MessageSendProxy.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:Rpc客户端消息处理   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import java.lang.reflect.InvocationHandler;  import java.lang.reflect.Method;  import java.util.UUID;  import newlandframework.netty.rpc.model.MessageRequest;    public class MessageSendProxy<T> implements InvocationHandler {        private Class<T> cls;        public MessageSendProxy(Class<T> cls) {          this.cls = cls;      }        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {          MessageRequest request = new MessageRequest();          request.setMessageId(UUID.randomUUID().toString());          request.setClassName(method.getDeclaringClass().getName());          request.setMethodName(method.getName());          request.settypeParameters(method.getParameterTypes());          request.setParameters(args);            MessageSendHandler handler = RpcServerLoader.getInstance().getMessageSendHandler();          MessageCallBack callBack = handler.sendRequest(request);          return callBack.start();      }  }  </code></pre>    <p>进一步发现MessageSendProxy其实是把消息发送给RpcServerLoader模块，它的代码如下：</p>    <pre>  <code class="language-java">/**   * @filename:RpcServerLoader.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:rpc服务器配置加载   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import io.netty.channel.EventLoopGroup;  import io.netty.channel.nio.NioEventLoopGroup;  import java.net.InetSocketAddress;  import java.util.concurrent.ThreadPoolExecutor;    public class RpcServerLoader {        private volatile static RpcServerLoader rpcServerLoader;      private final static String DELIMITER = ":";        //方法返回到Java虚拟机的可用的处理器数量      private final static int parallel = Runtime.getRuntime().availableProcessors() * 2;      //netty nio线程池      private EventLoopGroup eventLoopGroup = new NioEventLoopGroup(parallel);      private static ThreadPoolExecutor threadPoolExecutor = (ThreadPoolExecutor) RpcThreadPool.getExecutor(16, -1);      private MessageSendHandler messageSendHandler = null;        private RpcServerLoader() {      }        //并发双重锁定      public static RpcServerLoader getInstance() {          if (rpcServerLoader == null) {              synchronized (RpcServerLoader.class) {                  if (rpcServerLoader == null) {                      rpcServerLoader = new RpcServerLoader();                  }              }          }          return rpcServerLoader;      }        public void load(String serverAddress) {          String[] ipAddr = serverAddress.split(RpcServerLoader.DELIMITER);          if (ipAddr.length == 2) {              String host = ipAddr[0];              int port = Integer.parseInt(ipAddr[1]);              final InetSocketAddress remoteAddr = new InetSocketAddress(host, port);                threadPoolExecutor.submit(new MessageSendInitializeTask(eventLoopGroup, remoteAddr, this));          }      }        public void setMessageSendHandler(MessageSendHandler messageInHandler) {          this.messageSendHandler = messageInHandler;      }        public MessageSendHandler getMessageSendHandler() {          return messageSendHandler;      }        public void unLoad() {          messageSendHandler.close();          threadPoolExecutor.shutdown();          eventLoopGroup.shutdownGracefully();      }  }  </code></pre>    <p>好了，现在一次性给出RPC客户端消息编码、解码、处理的模块实现代码。</p>    <pre>  <code class="language-java">/**   * @filename:MessageSendInitializeTask.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:Rpc客户端线程任务处理   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import io.netty.bootstrap.Bootstrap;  import io.netty.channel.ChannelFuture;  import io.netty.channel.ChannelFutureListener;  import io.netty.channel.ChannelOption;  import io.netty.channel.EventLoopGroup;  import io.netty.channel.socket.nio.NioSocketChannel;  import java.net.InetSocketAddress;    public class MessageSendInitializeTask implements Runnable {        private EventLoopGroup eventLoopGroup = null;      private InetSocketAddress serverAddress = null;      private RpcServerLoader loader = null;        MessageSendInitializeTask(EventLoopGroup eventLoopGroup, InetSocketAddress serverAddress, RpcServerLoader loader) {          this.eventLoopGroup = eventLoopGroup;          this.serverAddress = serverAddress;          this.loader = loader;      }        public void run() {          Bootstrap b = new Bootstrap();          b.group(eventLoopGroup)                  .channel(NioSocketChannel.class).option(ChannelOption.SO_KEEPALIVE, true);          b.handler(new MessageSendChannelInitializer());            ChannelFuture channelFuture = b.connect(serverAddress);          channelFuture.addListener(new ChannelFutureListener() {              public void operationComplete(final ChannelFuture channelFuture) throws Exception {                  if (channelFuture.isSuccess()) {                      MessageSendHandler handler = channelFuture.channel().pipeline().get(MessageSendHandler.class);                      MessageSendInitializeTask.this.loader.setMessageSendHandler(handler);                  }              }          });      }  }  </code></pre>    <pre>  <code class="language-java">/**   * @filename:MessageSendChannelInitializer.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:Rpc客户端管道初始化   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import io.netty.channel.ChannelInitializer;  import io.netty.channel.ChannelPipeline;  import io.netty.channel.socket.SocketChannel;  import io.netty.handler.codec.LengthFieldBasedFrameDecoder;  import io.netty.handler.codec.LengthFieldPrepender;  import io.netty.handler.codec.serialization.ClassResolvers;  import io.netty.handler.codec.serialization.ObjectDecoder;  import io.netty.handler.codec.serialization.ObjectEncoder;    public class MessageSendChannelInitializer extends ChannelInitializer<SocketChannel> {        //ObjectDecoder 底层默认继承半包解码器LengthFieldBasedFrameDecoder处理粘包问题的时候，      //消息头开始即为长度字段，占据4个字节。这里出于保持兼容的考虑      final public static int MESSAGE_LENGTH = 4;        protected void initChannel(SocketChannel socketChannel) throws Exception {          ChannelPipeline pipeline = socketChannel.pipeline();          //ObjectDecoder的基类半包解码器LengthFieldBasedFrameDecoder的报文格式保持兼容。因为底层的父类LengthFieldBasedFrameDecoder          //的初始化参数即为super(maxObjectSize, 0, 4, 0, 4);          pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, MessageSendChannelInitializer.MESSAGE_LENGTH, 0, MessageSendChannelInitializer.MESSAGE_LENGTH));          //利用LengthFieldPrepender回填补充ObjectDecoder消息报文头          pipeline.addLast(new LengthFieldPrepender(MessageSendChannelInitializer.MESSAGE_LENGTH));          pipeline.addLast(new ObjectEncoder());          //考虑到并发性能，采用weakCachingConcurrentResolver缓存策略。一般情况使用:cacheDisabled即可          pipeline.addLast(new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.weakCachingConcurrentResolver(this.getClass().getClassLoader())));          pipeline.addLast(new MessageSendHandler());      }  }  </code></pre>    <pre>  <code class="language-java">/**   * @filename:MessageSendHandler.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:Rpc客户端处理模块   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import io.netty.buffer.Unpooled;  import io.netty.channel.Channel;  import io.netty.channel.ChannelFutureListener;  import io.netty.channel.ChannelHandlerContext;  import io.netty.channel.ChannelInboundHandlerAdapter;  import java.net.SocketAddress;  import java.util.concurrent.ConcurrentHashMap;  import newlandframework.netty.rpc.model.MessageRequest;  import newlandframework.netty.rpc.model.MessageResponse;    public class MessageSendHandler extends ChannelInboundHandlerAdapter {        private ConcurrentHashMap<String, MessageCallBack> mapCallBack = new ConcurrentHashMap<String, MessageCallBack>();        private volatile Channel channel;      private SocketAddress remoteAddr;        public Channel getChannel() {          return channel;      }        public SocketAddress getRemoteAddr() {          return remoteAddr;      }        public void channelActive(ChannelHandlerContext ctx) throws Exception {          super.channelActive(ctx);          this.remoteAddr = this.channel.remoteAddress();      }        public void channelRegistered(ChannelHandlerContext ctx) throws Exception {          super.channelRegistered(ctx);          this.channel = ctx.channel();      }        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {          MessageResponse response = (MessageResponse) msg;          String messageId = response.getMessageId();          MessageCallBack callBack = mapCallBack.get(messageId);          if (callBack != null) {              mapCallBack.remove(messageId);              callBack.over(response);          }      }        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {          ctx.close();      }        public void close() {          channel.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);      }        public MessageCallBack sendRequest(MessageRequest request) {          MessageCallBack callBack = new MessageCallBack(request);          mapCallBack.put(request.getMessageId(), callBack);          channel.writeAndFlush(request);          return callBack;      }  }  </code></pre>    <p>最后给出RPC服务端的实现。首先是通过spring自动加载RPC服务接口、接口实现容器绑定加载，初始化Netty主/从线程池等操作，具体是通过MessageRecvExecutor模块实现的，现在给出实现代码：</p>    <pre>  <code class="language-java">/**   * @filename:MessageRecvExecutor.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:Rpc服务器执行模块   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import io.netty.bootstrap.ServerBootstrap;  import io.netty.channel.ChannelFuture;  import io.netty.channel.ChannelOption;  import io.netty.channel.EventLoopGroup;  import io.netty.channel.nio.NioEventLoopGroup;  import io.netty.channel.socket.nio.NioServerSocketChannel;  import java.nio.channels.spi.SelectorProvider;  import java.util.Iterator;  import java.util.Map;  import java.util.Set;  import java.util.concurrent.ConcurrentHashMap;  import java.util.concurrent.ThreadFactory;  import java.util.concurrent.ThreadPoolExecutor;  import java.util.logging.Level;  import newlandframework.netty.rpc.model.MessageKeyVal;  import org.springframework.beans.BeansException;  import org.springframework.beans.factory.InitializingBean;  import org.springframework.context.ApplicationContext;  import org.springframework.context.ApplicationContextAware;    public class MessageRecvExecutor implements ApplicationContextAware, InitializingBean {        private String serverAddress;      private final static String DELIMITER = ":";        private Map<String, Object> handlerMap = new ConcurrentHashMap<String, Object>();        private static ThreadPoolExecutor threadPoolExecutor;        public MessageRecvExecutor(String serverAddress) {          this.serverAddress = serverAddress;      }        public static void submit(Runnable task) {          if (threadPoolExecutor == null) {              synchronized (MessageRecvExecutor.class) {                  if (threadPoolExecutor == null) {                      threadPoolExecutor = (ThreadPoolExecutor) RpcThreadPool.getExecutor(16, -1);                  }              }          }          threadPoolExecutor.submit(task);      }        public void setApplicationContext(ApplicationContext ctx) throws BeansException {          try {              MessageKeyVal keyVal = (MessageKeyVal) ctx.getBean(Class.forName("newlandframework.netty.rpc.model.MessageKeyVal"));              Map<String, Object> rpcServiceObject = keyVal.getMessageKeyVal();                Set s = rpcServiceObject.entrySet();              Iterator<Map.Entry<String, Object>> it = s.iterator();              Map.Entry<String, Object> entry;                while (it.hasNext()) {                  entry = it.next();                  handlerMap.put(entry.getKey(), entry.getValue());              }          } catch (ClassNotFoundException ex) {              java.util.logging.Logger.getLogger(MessageRecvExecutor.class.getName()).log(Level.SEVERE, null, ex);          }      }        public void afterPropertiesSet() throws Exception {          //netty的线程池模型设置成主从线程池模式，这样可以应对高并发请求          //当然netty还支持单线程、多线程网络IO模型，可以根据业务需求灵活配置          ThreadFactory threadRpcFactory = new NamedThreadFactory("NettyRPC ThreadFactory");                    //方法返回到Java虚拟机的可用的处理器数量          int parallel = Runtime.getRuntime().availableProcessors() * 2;                EventLoopGroup boss = new NioEventLoopGroup();          EventLoopGroup worker = new NioEventLoopGroup(parallel,threadRpcFactory,SelectorProvider.provider());                    try {              ServerBootstrap bootstrap = new ServerBootstrap();              bootstrap.group(boss, worker).channel(NioServerSocketChannel.class)                      .childHandler(new MessageRecvChannelInitializer(handlerMap))                      .option(ChannelOption.SO_BACKLOG, 128)                      .childOption(ChannelOption.SO_KEEPALIVE, true);                String[] ipAddr = serverAddress.split(MessageRecvExecutor.DELIMITER);                if (ipAddr.length == 2) {                  String host = ipAddr[0];                  int port = Integer.parseInt(ipAddr[1]);                  ChannelFuture future = bootstrap.bind(host, port).sync();                  System.out.printf("[author tangjie] Netty RPC Server start success ip:%s port:%d\n", host, port);                  future.channel().closeFuture().sync();              } else {                  System.out.printf("[author tangjie] Netty RPC Server start fail!\n");              }          } finally {              worker.shutdownGracefully();              boss.shutdownGracefully();          }      }  }  </code></pre>    <p>最后还是老规矩，给出RPC服务端消息编码、解码、处理的核心模块代码实现，具体如下：</p>    <pre>  <code class="language-java">/**   * @filename:MessageRecvChannelInitializer.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:Rpc服务端管道初始化   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import io.netty.channel.ChannelInitializer;  import io.netty.channel.ChannelPipeline;  import io.netty.channel.socket.SocketChannel;  import io.netty.handler.codec.LengthFieldBasedFrameDecoder;  import io.netty.handler.codec.LengthFieldPrepender;  import io.netty.handler.codec.serialization.ClassResolvers;  import io.netty.handler.codec.serialization.ObjectDecoder;  import io.netty.handler.codec.serialization.ObjectEncoder;  import java.util.Map;    public class MessageRecvChannelInitializer extends ChannelInitializer<SocketChannel> {        //ObjectDecoder 底层默认继承半包解码器LengthFieldBasedFrameDecoder处理粘包问题的时候，      //消息头开始即为长度字段，占据4个字节。这里出于保持兼容的考虑      final public static int MESSAGE_LENGTH = 4;      private Map<String, Object> handlerMap = null;        MessageRecvChannelInitializer(Map<String, Object> handlerMap) {          this.handlerMap = handlerMap;      }        protected void initChannel(SocketChannel socketChannel) throws Exception {          ChannelPipeline pipeline = socketChannel.pipeline();          //ObjectDecoder的基类半包解码器LengthFieldBasedFrameDecoder的报文格式保持兼容。因为底层的父类LengthFieldBasedFrameDecoder          //的初始化参数即为super(maxObjectSize, 0, 4, 0, 4);           pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, MessageRecvChannelInitializer.MESSAGE_LENGTH, 0, MessageRecvChannelInitializer.MESSAGE_LENGTH));          //利用LengthFieldPrepender回填补充ObjectDecoder消息报文头          pipeline.addLast(new LengthFieldPrepender(MessageRecvChannelInitializer.MESSAGE_LENGTH));          pipeline.addLast(new ObjectEncoder());          //考虑到并发性能，采用weakCachingConcurrentResolver缓存策略。一般情况使用:cacheDisabled即可          pipeline.addLast(new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.weakCachingConcurrentResolver(this.getClass().getClassLoader())));          pipeline.addLast(new MessageRecvHandler(handlerMap));      }  }  </code></pre>    <pre>  <code class="language-java">/**   * @filename:MessageRecvHandler.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:Rpc服务器消息处理   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import io.netty.channel.ChannelHandlerContext;  import io.netty.channel.ChannelInboundHandlerAdapter;  import java.util.Map;  import newlandframework.netty.rpc.model.MessageRequest;  import newlandframework.netty.rpc.model.MessageResponse;    public class MessageRecvHandler extends ChannelInboundHandlerAdapter {        private final Map<String, Object> handlerMap;        public MessageRecvHandler(Map<String, Object> handlerMap) {          this.handlerMap = handlerMap;      }        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {          MessageRequest request = (MessageRequest) msg;          MessageResponse response = new MessageResponse();          MessageRecvInitializeTask recvTask = new MessageRecvInitializeTask(request, response, handlerMap, ctx);          //不要阻塞nio线程，复杂的业务逻辑丢给专门的线程池          MessageRecvExecutor.submit(recvTask);      }        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {          //网络有异常要关闭通道          ctx.close();      }  }  </code></pre>    <pre>  <code class="language-java">/**   * @filename:MessageRecvInitializeTask.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:Rpc服务器消息线程任务处理   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import io.netty.channel.ChannelFuture;  import io.netty.channel.ChannelFutureListener;  import io.netty.channel.ChannelHandlerContext;  import java.util.Map;  import newlandframework.netty.rpc.model.MessageRequest;  import newlandframework.netty.rpc.model.MessageResponse;  import org.apache.commons.beanutils.MethodUtils;    public class MessageRecvInitializeTask implements Runnable {        private MessageRequest request = null;      private MessageResponse response = null;      private Map<String, Object> handlerMap = null;      private ChannelHandlerContext ctx = null;        public MessageResponse getResponse() {          return response;      }        public MessageRequest getRequest() {          return request;      }        public void setRequest(MessageRequest request) {          this.request = request;      }        MessageRecvInitializeTask(MessageRequest request, MessageResponse response, Map<String, Object> handlerMap, ChannelHandlerContext ctx) {          this.request = request;          this.response = response;          this.handlerMap = handlerMap;          this.ctx = ctx;      }        public void run() {          response.setMessageId(request.getMessageId());          try {              Object result = reflect(request);              response.setResult(result);          } catch (Throwable t) {              response.setError(t.toString());              t.printStackTrace();              System.err.printf("RPC Server invoke error!\n");          }            ctx.writeAndFlush(response).addListener(new ChannelFutureListener() {              public void operationComplete(ChannelFuture channelFuture) throws Exception {                  System.out.println("RPC Server Send message-id respone:" + request.getMessageId());              }          });      }        private Object reflect(MessageRequest request) throws Throwable {          String className = request.getClassName();          Object serviceBean = handlerMap.get(className);          String methodName = request.getMethodName();          Object[] parameters = request.getParameters();          return MethodUtils.invokeMethod(serviceBean, methodName, parameters);      }  }  </code></pre>    <p>然后是RPC消息处理的回调实现模块代码</p>    <pre>  <code class="language-java">/**   * @filename:MessageCallBack.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:Rpc消息回调   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.core;    import java.util.concurrent.TimeUnit;  import java.util.concurrent.locks.Condition;  import java.util.concurrent.locks.Lock;  import java.util.concurrent.locks.ReentrantLock;  import newlandframework.netty.rpc.model.MessageRequest;  import newlandframework.netty.rpc.model.MessageResponse;    public class MessageCallBack {        private MessageRequest request;      private MessageResponse response;      private Lock lock = new ReentrantLock();      private Condition finish = lock.newCondition();        public MessageCallBack(MessageRequest request) {          this.request = request;      }        public Object start() throws InterruptedException {          try {              lock.lock();              //设定一下超时时间，rpc服务器太久没有相应的话，就默认返回空吧。              finish.await(10*1000, TimeUnit.MILLISECONDS);              if (this.response != null) {                  return this.response.getResult();              } else {                  return null;              }          } finally {              lock.unlock();          }      }        public void over(MessageResponse reponse) {          try {              lock.lock();              finish.signal();              this.response = reponse;          } finally {              lock.unlock();          }      }  }  </code></pre>    <p>到此为止，NettyRPC的关键部分：服务端、客户端的模块已经通过Netty全部实现了。现在给出spring加载配置rpc-invoke-config.xml的内容：</p>    <pre>  <code class="language-java"><?xml version="1.0" encoding="UTF-8"?>  <beans xmlns="http://www.springframework.org/schema/beans"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xmlns:context="http://www.springframework.org/schema/context"         xsi:schemaLocation="http://www.springframework.org/schema/beans         http://www.springframework.org/schema/beans/spring-beans.xsd         http://www.springframework.org/schema/context         http://www.springframework.org/schema/context/spring-context.xsd">    <context:component-scan base-package="newlandframework.netty.rpc.core"/>    <context:property-placeholder location="classpath:newlandframework/netty/rpc/config/rpc-server.properties"/>    <bean id="rpcbean" class="newlandframework.netty.rpc.model.MessageKeyVal">      <property name="messageKeyVal">        <map>          <entry key="newlandframework.netty.rpc.servicebean.Calculate">            <ref bean="calc"/>          </entry>        </map>      </property>    </bean>    <bean id="calc" class="newlandframework.netty.rpc.servicebean.CalculateImpl"/>    <bean id="rpcServer" class="newlandframework.netty.rpc.core.MessageRecvExecutor">      <constructor-arg name="serverAddress" value="${rpc.server.addr}"/>    </bean>  </beans>  </code></pre>    <p>再贴出RPC服务绑定ip信息的配置文件：rpc-server.properties的内容。</p>    <pre>  <code class="language-java">#rpc server's ip address config  rpc.server.addr=127.0.0.1:18888  </code></pre>    <p>最后NettyRPC服务端启动方式参考如下：</p>    <pre>  <code class="language-java">new ClassPathXmlApplicationContext("newlandframework/netty/rpc/config/rpc-invoke-config.xml");  </code></pre>    <p>如果一切顺利，没有出现意外的话，控制台上面，会出现如下截图所示的情况：</p>    <p><img src="https://simg.open-open.com/show/d11aab4f09f1ca3c3f32ff6a73459090.jpg"></p>    <p>如果出现了，说明NettyRPC服务器，已经启动成功！</p>    <p>上面基于Netty的RPC服务器，并发处理性能如何呢？实践是检验真理的唯一标准，下面我们就来实战一下。</p>    <p>下面的测试案例，是基于RPC远程调用两数相加函数，并返回计算结果。客户端同时开1W个线程，同一时刻，瞬时发起并发计算请求，然后观察Netty的RPC服务器是否有正常应答回复响应，以及客户端是否有正常返回调用计算结果。值得注意的是，测试案例是基于1W个线程瞬时并发请求而设计的，并不是1W个线程循环发起请求。这两者对于衡量RPC服务器的并发处理性能，还是有很大差别的。当然，前者对于并发性能的处理要求，要高上很多很多。</p>    <p>现在，先给出RPC计算接口、RPC计算接口实现类的代码实现：</p>    <pre>  <code class="language-java">/**   * @filename:Calculate.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:计算器定义接口   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.servicebean;    public interface Calculate {      //两数相加      int add(int a, int b);  }  </code></pre>    <pre>  <code class="language-java">/**   * @filename:CalculateImpl.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:计算器定义接口实现   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.servicebean;    public class CalculateImpl implements Calculate {      //两数相加      public int add(int a, int b) {          return a + b;      }  }  </code></pre>    <p>下面是瞬时并发RPC请求的测试样例：</p>    <pre>  <code class="language-java">/**   * @filename:CalcParallelRequestThread.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:并发线程模拟   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.servicebean;    import newlandframework.netty.rpc.core.MessageSendExecutor;  import java.util.concurrent.CountDownLatch;  import java.util.logging.Level;  import java.util.logging.Logger;    public class CalcParallelRequestThread implements Runnable {        private CountDownLatch signal;      private CountDownLatch finish;      private MessageSendExecutor executor;      private int taskNumber = 0;        public CalcParallelRequestThread(MessageSendExecutor executor, CountDownLatch signal, CountDownLatch finish, int taskNumber) {          this.signal = signal;          this.finish = finish;          this.taskNumber = taskNumber;          this.executor = executor;      }        public void run() {          try {              signal.await();                Calculate calc = executor.execute(Calculate.class);              int add = calc.add(taskNumber, taskNumber);              System.out.println("calc add result:[" + add + "]");                finish.countDown();          } catch (InterruptedException ex) {              Logger.getLogger(CalcRequestThread.class.getName()).log(Level.SEVERE, null, ex);          }      }  }  </code></pre>    <pre>  <code class="language-java">/**   * @filename:RpcParallelTest.java   *   * Newland Co. Ltd. All rights reserved.   *   * @Description:rpc并发测试代码   * @author tangjie   * @version 1.0   *   */  package newlandframework.netty.rpc.servicebean;    import java.util.concurrent.CountDownLatch;  import newlandframework.netty.rpc.core.MessageSendExecutor;  import org.apache.commons.lang.time.StopWatch;    public class RpcParallelTest {        public static void main(String[] args) throws Exception {          final MessageSendExecutor executor = new MessageSendExecutor("127.0.0.1:18888");          //并行度10000          int parallel = 10000;            //开始计时          StopWatch sw = new StopWatch();          sw.start();            CountDownLatch signal = new CountDownLatch(1);          CountDownLatch finish = new CountDownLatch(parallel);            for (int index = 0; index < parallel; index++) {              CalcParallelRequestThread client = new CalcParallelRequestThread(executor, signal, finish, index);              new Thread(client).start();          }                    //10000个并发线程瞬间发起请求操作          signal.countDown();          finish.await();                    sw.stop();            String tip = String.format("RPC调用总共耗时: [%s] 毫秒", sw.getTime());          System.out.println(tip);            executor.stop();      }  }  </code></pre>    <p>好了，现在先启动NettyRPC服务器，确认没有问题之后，运行并发RPC请求客户端，看下客户端打印的计算结果，以及处理耗时。</p>    <p><img src="https://simg.open-open.com/show/47b038d97d60b884ffd2665bfe579382.jpg"></p>    <p>从上面来看，10000个瞬时RPC计算请求，总共耗时接近11秒。我们在来看下NettyRPC的服务端运行情况，如下所示：</p>    <p><img src="https://simg.open-open.com/show/05220feeb5cb95de3293fa48f888d5b4.jpg"></p>    <p>可以很清楚地看到，RPC服务端都有收到客户端发起的RPC计算请求，并返回消息应答。</p>    <p>最后我们还是要分别验证一下，RPC服务端是否存在丢包、粘包、IO阻塞的情况？1W个并发计算请求，是否成功接收处理并应答了？实际情况说明一切，看下图所示：</p>    <p><img src="https://simg.open-open.com/show/a213eccb330c3f50c51b60aa18b181b1.jpg"></p>    <p>非常给力，RPC的服务端确实成功接收到了客户端发起的1W笔瞬时并发计算请求，并且成功应答处理了。并没有出现：丢包、粘包、IO阻塞的情况。再看下RPC客户端，是否成功得到计算结果的应答返回了呢？</p>    <p><img src="https://simg.open-open.com/show/246d7af439ca0038894f71499a5dde30.jpg"></p>    <p>很好，RPC的客户端，确实收到了RPC服务端计算的1W笔加法请求的计算结果，而且耗时接近11秒。由此可见，基于Netty+业务线程池的NettyRPC服务器，应对并发多线程RPC请求，处理起来是得心应手，游刃有余！</p>    <p>最后，本文通过Netty这个NIO框架，实现了一个很简单的“高性能”的RPC服务器，代码虽然写出来了，但是还是有一些值得改进的地方，比如：</p>    <p>1、对象序列化传输可以支持目前主流的序列化框架：protobuf、JBoss Marshalling、Avro等等。</p>    <p>2、Netty的线程模型可以根据业务需求，进行定制。因为，并不是每笔业务都需要这么强大的并发处理性能。</p>    <p>3、目前RPC计算只支持一个RPC服务接口映射绑定一个对应的实现，后续要支持一对多的情况。</p>    <p>4、业务线程池的启动参数、线程池并发阻塞容器模型等等，可以配置化管理。</p>    <p>5、Netty的Handler处理部分，对于复杂的业务逻辑，现在是统一分派到特定的线程池进行后台异步处理。当然你还可以考虑JMS（消息队列）方式进行解耦，统一分派给消息队列的订阅者，统一处理。目前实现JMS的开源框架也有很多，ActiveMQ、RocketMQ等等，都可以考虑。</p>    <p>本文实现的NettyRPC，对于面前的您而言，一定还有很多地方，可以加以完善和改进，优化改进的工作就交给您自由发挥了。</p>    <p>由于本人技术能力、认知水平有限。本文中有说不对的地方，恳请园友们批评指正！不吝赐教！最后，感谢面前的您，耐心的阅读完本文，相信现在的你，对于Java开发高性能的服务端应用，又有了一个更深入的了解！本文算是对我Netty学习成果的阶段性总结，后续有时间，我还会继续推出Netty工业级开发的相关文章，敬请期待！</p>    <p> </p>    <p>来自： <a href="/misc/goto?guid=4959675257606833622" rel="nofollow">http://www.cnblogs.com/jietang/p/5615681.html</a></p>    <p> </p>