netty心跳检测 heartbeat（五）

HeartBeat心跳

心跳检测的必要性 

1.集群心跳检测，避免网络中断

2.数据同步：主节点写日志，从节点每隔一段时间拉取主节点日志。

心跳检测存在的意义：

客户端和服务端已经建立了长连接，客户端开飞行模式，关机，关闭wifi，服务端不会(感知)收到通知(handRemoved)并关闭连接。

核心事件 ：

ChannelInboundHandlerAdapter类的userEventTriggered事件

心跳检测服务端代码 ：

server启动类 ：

 1 public class HeartBeatServer {
 2
 3     public static void main(String[] args) throws InterruptedException {
 4
 5         EventLoopGroup bossGroup = new NioEventLoopGroup();
 6         EventLoopGroup workerGroup = new NioEventLoopGroup();
 7
 8         try{
 9             ServerBootstrap serverBootstrap = new ServerBootstrap();
10             serverBootstrap.group(bossGroup,workerGroup).
11                     channel(NioServerSocketChannel.class)
12                     .handler(new LoggingHandler(LogLevel.INFO))
13                     .childHandler(new MyHeartBeatInitializer());
14
15             ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
16             channelFuture.channel().closeFuture().sync();
17         }finally {
18             bossGroup.shutdownGracefully();
19             workerGroup.shutdownGracefully();
20         }
21
22     }
23
24 }

心跳检测初始化类 ：

 1 public class MyHeartBeatInitializer extends ChannelInitializer<SocketChannel> {
 2     @Override
 3     protected void initChannel(SocketChannel ch) throws Exception {
 4
 5         ChannelPipeline channelPipeline = ch.pipeline();
 6
 7         channelPipeline.addLast(new IdleStateHandler(3,7,10, TimeUnit.SECONDS));
 8         channelPipeline.addLast(new MyHeartBeatHandler());
 9
10     }
11 }

心跳检测逻辑处理handler：

 1 public class MyHeartBeatHandler extends ChannelInboundHandlerAdapter {
 2
 3     @Override
 4     public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
 5
 6         if(evt instanceof IdleStateEvent){
 7             IdleStateEvent idleStateEvent = (IdleStateEvent)evt;
 8
 9             String eventType = null;
10
11             switch (idleStateEvent.state()){
12                 case READER_IDLE:
13                     eventType = "读空闲";
14                     break;
15                 case WRITER_IDLE:
16                     eventType = "写空闲";
17                     break;
18                 case ALL_IDLE:
19                     eventType = "读写空闲";
20                     break;
21
22             }
23
24             System.out.println(ctx.channel().remoteAddress()+" 超时事件："+eventType);
25
26             ctx.channel().close();
27         }
28
29     }
30 }