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Netty Client重连实现

2016-05-02 20:32 369 查看

from:http://itindex.net/detail/54161-netty-client

当我们用Netty实现一个TCP client时，我们当然希望当连接断掉的时候Netty能够自动重连。
Netty Client有两种情况下需要重连：

Netty Client启动的时候需要重连
在程序运行中连接断掉需要重连。
对于第一种情况，Netty的作者在stackoverflow上给出了解决方案，
对于第二种情况，Netty的例子uptime中实现了一种解决方案。

而Thomas在他的文章中提供了这两种方式的实现的例子。

实现ChannelFutureListener 用来启动时监测是否连接成功，不成功的话重试：

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public class Client        {          private EventLoopGroup loop = new NioEventLoopGroup();          public static void main( String[] args )          {            new Client().run();          }          public Bootstrap createBootstrap(Bootstrap bootstrap, EventLoopGroup eventLoop) {            if (bootstrap != null) {              final MyInboundHandler handler = new MyInboundHandler(this);              bootstrap.group(eventLoop);              bootstrap.channel(NioSocketChannel.class);              bootstrap.option(ChannelOption.SO_KEEPALIVE, true);              bootstrap.handler(new ChannelInitializer<SocketChannel>() {                @Override                protected void initChannel(SocketChannel socketChannel) throws Exception {                  socketChannel.pipeline().addLast(handler);                }              });              bootstrap.remoteAddress("localhost", 8888);            bootstrap.connect().addListener(new ConnectionListener(this));           }            return bootstrap;          }          public void run() {            createBootstrap(new Bootstrap(), loop);        }        }

ConnectionListener 负责重连：

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public class ConnectionListener implements ChannelFutureListener {         private Client client;         public ConnectionListener(Client client) {           this.client = client;         }         @Override         public void operationComplete(ChannelFuture channelFuture) throws Exception {           if (!channelFuture.isSuccess()) {             System.out.println("Reconnect");             final EventLoop loop = channelFuture.channel().eventLoop();             loop.schedule(new Runnable() {               @Override               public void run() {                 client.createBootstrap(new Bootstrap(), loop);               }             }, 1L, TimeUnit.SECONDS);           }         }       }

同样在ChannelHandler监测连接是否断掉，断掉的话也要重连：

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public class MyInboundHandler extends SimpleChannelInboundHandler {          private Client client;          public MyInboundHandler(Client client) {            this.client = client;          }          @Override          public void channelInactive(ChannelHandlerContext ctx) throws Exception {            final EventLoop eventLoop = ctx.channel().eventLoop();            eventLoop.schedule(new Runnable() {              @Override              public void run() {                client.createBootstrap(new Bootstrap(), eventLoop);              }            }, 1L, TimeUnit.SECONDS);            super.channelInactive(ctx);          }        }

参考文档

http://stackoverflow.com/questions/19739054/whats-the-best-way-to-reconnect-after-connection-closed-in-netty
https://github.com/netty/netty/blob/master/example/src/main/java/io/netty/example/uptime/UptimeClientHandler.java
http://tterm.blogspot.jp/2014/03/netty-tcp-client-with-reconnect-handling.html
ctx.close vs ctx.channel().close
ctx.write vs ctx.channel().write

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