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> 本文由用户 sdangel 自行上传分享，仅供网友学习交流。所有权归原作者，若您的权利被侵害，请联系管理员。
转载本站原创文章，请注明出处，并保留原始链接、图片水印。
本站是一个以用户分享为主的开源技术平台，欢迎各类分享！