JAVA RPC (九) netty服务端解析

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

 1   @Override
 2     public void run() {
 3         try {
 4             if (Epoll.isAvailable ()) {
 5                 bossGroup = new EpollEventLoopGroup (serverPublisher.bossThreadCount==0?AbstractKoalsServerPublisher.DEFAULT_EVENT_LOOP_THREADS:serverPublisher.bossThreadCount);
 6                 workerGroup = new EpollEventLoopGroup ( serverPublisher.workThreadCount==0? AbstractKoalsServerPublisher.DEFAULT_EVENT_LOOP_THREADS*2:serverPublisher.workThreadCount);
 7             } else {
 8                 bossGroup = new NioEventLoopGroup (serverPublisher.bossThreadCount==0?AbstractKoalsServerPublisher.DEFAULT_EVENT_LOOP_THREADS:serverPublisher.bossThreadCount);
 9                 workerGroup = new NioEventLoopGroup ( serverPublisher.workThreadCount==0? AbstractKoalsServerPublisher.DEFAULT_EVENT_LOOP_THREADS*2:serverPublisher.workThreadCount );
10             }
11             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 ()));
12 
13             ServerBootstrap b = new ServerBootstrap ();
14             b.group ( bossGroup, workerGroup ).channel ( workerGroup instanceof EpollEventLoopGroup ? EpollServerSocketChannel.class : NioServerSocketChannel.class )
15                     .handler ( new LoggingHandler ( LogLevel.INFO ) )
16                     .childHandler ( new NettyServerInitiator (serverPublisher,executorService))
17                     .option ( ChannelOption.SO_BACKLOG, 1024 )
18                     .option ( ChannelOption.SO_REUSEADDR, true )
19                     .option ( ChannelOption.SO_KEEPALIVE, true );
20             Channel ch = b.bind ( serverPublisher.port ).sync ().channel ();
21             Runtime.getRuntime().addShutdownHook(new Thread(){
22                 @Override
23                 public void run(){
24                     logger.info ( "Shutdown by Runtime" );
25                     if(zookeeperServer != null){
26                         zookeeperServer.destroy ();
27                     }
28                     logger.info ( "wait for service over 3000ms" );
29                     try {
30                         Thread.sleep ( 3000 );
31                     } catch (Exception e) {
32                     }
33                     if(executorService!=null){
34                         executorService.shutdown ();
35                     }
36                     if(bossGroup != null) bossGroup.shutdownGracefully ();
37                     if(workerGroup != null) workerGroup.shutdownGracefully ();
38                 }
39             });
40 
41             if(StringUtils.isNotEmpty ( serverPublisher.zkpath )){
42                 ZookServerConfig zookServerConfig = new ZookServerConfig ( serverPublisher.zkpath,serverPublisher.serviceInterface.getName (),serverPublisher.env,serverPublisher.port,serverPublisher.weight,"netty" );
43                 zookeeperServer = new ZookeeperServer ( zookServerConfig );
44                 zookeeperServer.init ();
45             }
46         } catch ( Exception e){
47             logger.error ( "NettyServer start faid !",e );
48             if(bossGroup != null) bossGroup.shutdownGracefully ();
49             if(workerGroup != null) workerGroup.shutdownGracefully ();
50         }
51 
52         logger.info("netty server init success server={}",serverPublisher);
53 
54     }

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。

 1  Runtime.getRuntime().addShutdownHook(new Thread(){
 2                 @Override
 3                 public void run(){
 4                     logger.info ( "Shutdown by Runtime" );
 5                     if(zookeeperServer != null){
 6                         zookeeperServer.destroy ();
 7                     }
 8                     logger.info ( "wait for service over 3000ms" );
 9                     try {
10                         Thread.sleep ( 3000 );
11                     } catch (Exception e) {
12                     }
13                     if(executorService!=null){
14                         executorService.shutdown ();
15                     }
16                     if(bossGroup != null) bossGroup.shutdownGracefully ();
17                     if(workerGroup != null) workerGroup.shutdownGracefully ();
18                 }
19             });

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
 1 package netty.hanlder;
 2 
 3 import io.netty.buffer.ByteBuf;
 4 import io.netty.channel.ChannelHandlerContext;
 5 import io.netty.handler.codec.ByteToMessageDecoder;
 6 import org.slf4j.Logger;
 7 import org.slf4j.LoggerFactory;
 8 import server.KoalasServerPublisher;
 9 
10 import java.util.List;
11 /**
12  * Copyright (C) 2018
13  * All rights reserved
14  * User: yulong.zhang
15  * Date:2018年11月23日11:13:33
16  */
17 public class KoalasDecoder extends ByteToMessageDecoder {
18 
19     private final static Logger logger = LoggerFactory.getLogger ( KoalasDecoder.class );
20 
21     @Override
22     protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) {
23 
24         try {
25             if (in.readableBytes () < 4) {
26                 return;
27             }
28 
29             in.markReaderIndex ();
30             byte[] b = new byte[4];
31             in.readBytes ( b );
32 
33             int length = decodeFrameSize ( b );
34 
35             if (in.readableBytes () < length) {
36                 //reset the readerIndex
37                 in.resetReaderIndex ();
38                 return;
39             }
40 
41             in.resetReaderIndex ();
42             ByteBuf fream = in.readRetainedSlice ( 4 + length );
43             in.resetReaderIndex ();
44 
45             in.skipBytes ( 4 + length );
46             out.add ( fream );
47         } catch (Exception e) {
48             logger.error ( "decode error",e );
49         }
50 
51     }
52 
53     public static final int decodeFrameSize(byte[] buf) {
54         return (buf[0] & 255) << 24 | (buf[1] & 255) << 16 | (buf[2] & 255) << 8 | buf[3] & 255;
55     }
56 }

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
 1            try {
 2                 tprocessor.process ( in,out );
 3                 ctx.writeAndFlush (outputStream);
 4                 if(transaction!=null && cat)
 5                     transaction.setStatus ( Transaction.SUCCESS );
 6             } catch (Exception e) {
 7                 if(transaction!=null && cat)
 8                     transaction.setStatus ( e );
 9                 logger.error ( e.getMessage () + ErrorType.APPLICATION+",className:"+className,e );
10                 handlerException(this.b,ctx,e,ErrorType.APPLICATION,privateKey,publicKey,thriftNative);
11             }

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！

 

【推广】 免费学中医，健康全家人
原文地址：https://www.cnblogs.com/zyl2016/p/10840087.html