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Implementering af keep-alive beskeder i Netty ved hjælp af WriteTimeoutHandler

Netty

Til Netty 4.0 og nyere , bør du udvide ChannelDuplexHandler som i eksempel fra IdleStateHandler dokumentation :

 // An example that sends a ping message when there is no outbound traffic
 // for 30 seconds.  The connection is closed when there is no inbound traffic
 // for 60 seconds.

 public class MyChannelInitializer extends ChannelInitializer<Channel> {
     @Override
     public void initChannel(Channel channel) {
         channel.pipeline().addLast("idleStateHandler", new IdleStateHandler(60, 30, 0));
         channel.pipeline().addLast("myHandler", new MyHandler());
     }
 }

 // Handler should handle the IdleStateEvent triggered by IdleStateHandler.
 public class MyHandler extends ChannelDuplexHandler {
     @Override
     public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
         if (evt instanceof IdleStateEvent) {
             IdleStateEvent e = (IdleStateEvent) evt;
             if (e.state() == IdleState.READER_IDLE) {
                 ctx.close();
             } else if (e.state() == IdleState.WRITER_IDLE) {
                 ctx.writeAndFlush(new PingMessage());
             }
         }
     }
 }

Jeg vil foreslå at tilføje IdleStateHandler og derefter tilføje din tilpassede implementering af IdleStateAwareUpstreamHandler, som kan reagere på inaktiv tilstand. Dette fungerer meget godt for mig på mange forskellige projekter.

Javadocs viser følgende eksempel, som du kan bruge som base for din implementering:

public class MyPipelineFactory implements ChannelPipelineFactory {

    private final Timer timer;
    private final ChannelHandler idleStateHandler;

    public MyPipelineFactory(Timer timer) {
        this.timer = timer;
        this.idleStateHandler = new IdleStateHandler(timer, 60, 30, 0);
        // timer must be shared.
    }

    public ChannelPipeline getPipeline() {
        return Channels.pipeline(
            idleStateHandler,
            new MyHandler());
    }
}

// Handler should handle the IdleStateEvent triggered by IdleStateHandler.
public class MyHandler extends IdleStateAwareChannelHandler {

    @Override
    public void channelIdle(ChannelHandlerContext ctx, IdleStateEvent e) {
        if (e.getState() == IdleState.READER_IDLE) {
            e.getChannel().close();
        } else if (e.getState() == IdleState.WRITER_IDLE) {
            e.getChannel().write(new PingMessage());
        }
    }
}

ServerBootstrap bootstrap = ...;
Timer timer = new HashedWheelTimer();
...
bootstrap.setPipelineFactory(new MyPipelineFactory(timer));
...

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