JAVA RPC (九) netty服务端解析

时间：2021-11-20 12:36:51

源码地址：https://gitee.com/a1234567891/koalas-rpc

企业生产级百亿日PV高可用可拓展的RPC框架。理论上并发数量接近服务器带宽，客户端采用thrift协议，服务端支持netty和thrift的TThreadedSelectorServer半同步半异步线程模型，支持动态扩容，服务上下线，权重动态，可用性配置，页面流量统计，支持trace跟踪等，天然接入cat支持数据大盘展示等，持续为个人以及中小型公司提供可靠的RPC框架技术方案，贴上

   @Override

     public void run() {

         try {

             if (Epoll.isAvailable ()) {

                 bossGroup = new EpollEventLoopGroup (serverPublisher.bossThreadCount==0?AbstractKoalsServerPublisher.DEFAULT_EVENT_LOOP_THREADS:serverPublisher.bossThreadCount);

                 workerGroup = new EpollEventLoopGroup ( serverPublisher.workThreadCount==0? AbstractKoalsServerPublisher.DEFAULT_EVENT_LOOP_THREADS*2:serverPublisher.workThreadCount);

             } else {

                 bossGroup = new NioEventLoopGroup (serverPublisher.bossThreadCount==0?AbstractKoalsServerPublisher.DEFAULT_EVENT_LOOP_THREADS:serverPublisher.bossThreadCount);

                 workerGroup = new NioEventLoopGroup ( serverPublisher.workThreadCount==0? AbstractKoalsServerPublisher.DEFAULT_EVENT_LOOP_THREADS*2:serverPublisher.workThreadCount );

             }

             executorService = KoalasThreadedSelectorWorkerExcutorUtil.getWorkerExecutorWithQueue (serverPublisher.koalasThreadCount==0?AbstractKoalsServerPublisher.DEFAULT_KOALAS_THREADS:serverPublisher.koalasThreadCount,serverPublisher.koalasThreadCount==0?AbstractKoalsServerPublisher.DEFAULT_KOALAS_THREADS:serverPublisher.koalasThreadCount,serverPublisher.workQueue,new KoalasDefaultThreadFactory (serverPublisher.serviceInterface.getName ()));

             ServerBootstrap b = new ServerBootstrap ();

             b.group ( bossGroup, workerGroup ).channel ( workerGroup instanceof EpollEventLoopGroup ? EpollServerSocketChannel.class : NioServerSocketChannel.class )

                     .handler ( new LoggingHandler ( LogLevel.INFO ) )

                     .childHandler ( new NettyServerInitiator (serverPublisher,executorService))

                     .option ( ChannelOption.SO_BACKLOG, 1024 )

                     .option ( ChannelOption.SO_REUSEADDR, true )

                     .option ( ChannelOption.SO_KEEPALIVE, true );

             Channel ch = b.bind ( serverPublisher.port ).sync ().channel ();

             Runtime.getRuntime().addShutdownHook(new Thread(){

                 @Override

                 public void run(){

                     logger.info ( "Shutdown by Runtime" );

                     if(zookeeperServer != null){

                         zookeeperServer.destroy ();

                     }

                     logger.info ( "wait for service over 3000ms" );

                     try {

                         Thread.sleep ( 3000 );

                     } catch (Exception e) {

                     }

                     if(executorService!=null){

                         executorService.shutdown ();

                     }

                     if(bossGroup != null) bossGroup.shutdownGracefully ();

                     if(workerGroup != null) workerGroup.shutdownGracefully ();

                 }

             });

             if(StringUtils.isNotEmpty ( serverPublisher.zkpath )){

                 ZookServerConfig zookServerConfig = new ZookServerConfig ( serverPublisher.zkpath,serverPublisher.serviceInterface.getName (),serverPublisher.env,serverPublisher.port,serverPublisher.weight,"netty" );

                 zookeeperServer = new ZookeeperServer ( zookServerConfig );

                 zookeeperServer.init ();

             }

         } catch ( Exception e){

             logger.error ( "NettyServer start faid !",e );

             if(bossGroup != null) bossGroup.shutdownGracefully ();

             if(workerGroup != null) workerGroup.shutdownGracefully ();

         }

         logger.info("netty server init success server={}",serverPublisher);

     }

首先开启NIO服务，由系统内核来判断是否支持epoll-EpollEventLoopGroup,如果不支持epoll采用IO多路复用的方式EpollEventLoopGroup，然后声明一个用户自定义线程池，这里有不清楚的读者肯定会问，netty本身支持连接线程和IO线程，为什么还要自定义声明自定义线程池，原因是假设在IO线程池中做的业务非常复杂，大量耗时，这样就会阻塞了netty线程的IO处理速度，影响吞吐量，这也就是reactor模型的设计理念，不让业务干扰连接线程和IO读写线程。NettyServerInitiator就是实际处理的业务handle了。

  Runtime.getRuntime().addShutdownHook(new Thread(){

                 @Override

                 public void run(){

                     logger.info ( "Shutdown by Runtime" );

                     if(zookeeperServer != null){

                         zookeeperServer.destroy ();

                     }

                     logger.info ( "wait for service over 3000ms" );

                     try {

                         Thread.sleep ( 3000 );

                     } catch (Exception e) {

                     }

                     if(executorService!=null){

                         executorService.shutdown ();

                     }

                     if(bossGroup != null) bossGroup.shutdownGracefully ();

                     if(workerGroup != null) workerGroup.shutdownGracefully ();

                 }

             });

手动关闭钩子，服务关闭的时候要主动关闭节点信息。下面来看一下hander拦截器

package netty.initializer;

import io.netty.channel.ChannelInitializer;

import io.netty.channel.socket.SocketChannel;

import netty.hanlder.KoalasDecoder;

import netty.hanlder.KoalasEncoder;

import netty.hanlder.KoalasHandler;

import org.apache.thrift.TProcessor;

import server.config.AbstractKoalsServerPublisher;

import java.util.concurrent.ExecutorService;

/**

 * Copyright (C) 2018

 * All rights reserved

 * User: yulong.zhang

 * Date:2018年11月23日11:13:33

 */

public class NettyServerInitiator extends ChannelInitializer<SocketChannel> {

    private ExecutorService executorService;

    private  AbstractKoalsServerPublisher serverPublisher;

    public NettyServerInitiator(AbstractKoalsServerPublisher serverPublisher,ExecutorService executorService){

        this.serverPublisher = serverPublisher;

        this.executorService = executorService;

    }

    @Override

    protected void initChannel(SocketChannel ch) {

        ch.pipeline ().addLast ( "decoder",new KoalasDecoder () );

        ch.pipeline ().addLast ( "encoder",new KoalasEncoder ());

        ch.pipeline ().addLast ( "handler",new KoalasHandler (serverPublisher,executorService) );

    }

}
decode负责拆包。encoder负责装包，handler是真正业务处理的逻辑，所有的业务处理都在这里的线程池中运行，结果通过ChannelHandlerContext 异步的返回给client端，通过这种方式真正的实现了reactor
下面我们看看拆包处理
 package netty.hanlder;

 import io.netty.buffer.ByteBuf;

 import io.netty.channel.ChannelHandlerContext;

 import io.netty.handler.codec.ByteToMessageDecoder;

 import org.slf4j.Logger;

 import org.slf4j.LoggerFactory;

 import server.KoalasServerPublisher;

 import java.util.List;

 /**

  * Copyright (C) 2018

  * All rights reserved

  * User: yulong.zhang

  * Date:2018年11月23日11:13:33

  */

 public class KoalasDecoder extends ByteToMessageDecoder {

     private final static Logger logger = LoggerFactory.getLogger ( KoalasDecoder.class );

     @Override

     protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) {

         try {

             if (in.readableBytes () < 4) {

                 return;

             }

             in.markReaderIndex ();

             byte[] b = new byte[4];

             in.readBytes ( b );

             int length = decodeFrameSize ( b );

             if (in.readableBytes () < length) {

                 //reset the readerIndex

                 in.resetReaderIndex ();

                 return;

             }

             in.resetReaderIndex ();

             ByteBuf fream = in.readRetainedSlice ( 4 + length );

             in.resetReaderIndex ();

             in.skipBytes ( 4 + length );

             out.add ( fream );

         } catch (Exception e) {

             logger.error ( "decode error",e );

         }

     }

     public static final int decodeFrameSize(byte[] buf) {

         return (buf[0] & 255) << 24 | (buf[1] & 255) << 16 | (buf[2] & 255) << 8 | buf[3] & 255;

     }

 }

通过读取四个字节的长度来决定消息体长度，然后根据消息体长度来读取所有的字节流数据。decodeFrameSize方法将四个字节流转成int类型。KoalasHandler处理器逻辑比较复杂，我们只看核心的内容，首先通过thrift解析字节流来获取transport

            ByteArrayInputStream inputStream = new ByteArrayInputStream ( b );

            ByteArrayOutputStream outputStream = new ByteArrayOutputStream (  );

            TIOStreamTransport tioStreamTransportInput = new TIOStreamTransport (  inputStream);

            TIOStreamTransport tioStreamTransportOutput = new TIOStreamTransport (  outputStream);

            TKoalasFramedTransport inTransport = new TKoalasFramedTransport ( tioStreamTransportInput,2048000 );

            inTransport.setReadMaxLength_ ( maxLength );

            TKoalasFramedTransport outTransport = new TKoalasFramedTransport ( tioStreamTransportOutput,2048000,ifUserProtocol );

最终扔到线程池里去执行，将当前IO线程释放给下一个任务。

           try {

                executorService.execute ( new NettyRunable (  ctx,in,out,outputStream,localTprocessor,b,privateKey,publicKey,className,methodName,koalasTrace,cat));

            } catch (RejectedExecutionException e){

                logger.error ( e.getMessage ()+ErrorType.THREAD+",className:" +className,e );

                handlerException(b,ctx,e,ErrorType.THREAD,privateKey,publicKey,thriftNative);

            }
RejectedExecutionException来负责当线程池不够用的时候返回给client端异常，因为server端的业务处理能力有限，所以这里适当的做了一下服务端保护防止雪崩的问题。当发现server端有大量的
RejectedExecutionException抛出，说明单机已经无法满足业务请求了，需要横向拓展机器来进行负载均衡。用户实际的业务执行是在Runable里，我们看看他到底做了什么
            try {

                 tprocessor.process ( in,out );

                 ctx.writeAndFlush (outputStream);

                 if(transaction!=null && cat)

                     transaction.setStatus ( Transaction.SUCCESS );

             } catch (Exception e) {

                 if(transaction!=null && cat)

                     transaction.setStatus ( e );

                 logger.error ( e.getMessage () + ErrorType.APPLICATION+",className:"+className,e );

                 handlerException(this.b,ctx,e,ErrorType.APPLICATION,privateKey,publicKey,thriftNative);

             }

通过thrift的process来执行业务逻辑，将结果通过ctx.writeAndFlush (outputStream)，返回给client端。在catch里处理当出现异常之后返回给client端异常结果。这样netty server的实现就全部结束了，thrift服务端解析相关内容我们下一篇来说，里面当中有很多细节需要读者是跟着源码阅读，如果有问题欢迎加群825199617来交流，更多spring，spring mvc，aop，jdk等源码交流等你来！

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