由于netty采用了事件機制,是以給鍊路監測和連接配接管理帶來了一些麻煩,是以最好給鍊路加上心跳處理
(1) 伺服器端關鍵點,主要在initpipe中和實作IdleStateAwareChannelHandler.
pipeline.addLast("timeout", new IdleStateHandler(timer, 10, 10, 0));//此兩項為添加心跳機制 10秒檢視一次線上的用戶端channel是否空閑,IdleStateHandler為netty jar包中提供的類
pipeline.addLast("hearbeat", new Heartbeat());
如果要捕獲檢測結果,需要繼承IdleStateAwareChannelHandler,來判斷用戶端是否存在,但是這種機制還得一個心跳包發送來檢測。
public class Heartbeat extends IdleStateAwareChannelHandler{
int i = 0;
@Override
public void channelIdle(ChannelHandlerContext ctx, IdleStateEvent e)
throws Exception {
// TODO Auto-generated method stub
super.channelIdle(ctx, e);
if(e.getState() == IdleState.WRITER_IDLE)
i++;
if(i==3){
e.getChannel().close();
System.out.println("掉了。");
}
}
}
(2)用戶端關鍵點,也在booststrap,initpipe和IdleStateAwareChannelHandler
bootstrap.setOption("allIdleTime","5"); //這裡,很重要
pipeline.addLast("timeout", new IdleStateHandler(timer, 0, 0, 10));
pipeline.addLast("idleHandler", new ClientIdleHandler());
實作IdleStateAwareChannelHandler 的handler負責定時發送檢測包
public class ClientIdleHandler extends IdleStateAwareChannelHandler {
final Logger logger = LoggerFactory.getLogger(ClientIdleHandler.class);
@Override
public void channelIdle(ChannelHandlerContext ctx, IdleStateEvent e) throws Exception {
if( e.getState() == IdleState.ALL_IDLE){
logger.debug("鍊路空閑!發送心跳!S:{} - C:{} idleState:{}", new Object[]{ctx.getChannel().getRemoteAddress(), ctx.getChannel().getLocalAddress() , e.getState()});
e.getChannel().write(MessageHelper.buildMessageEcho());
super.channelIdle(ctx, e);
}
}
}
此外為了獲得一些業務阻塞異常導緻一些網路不确認狀态,采取辦法是:用發送upstream的異常來通知解決。
public void exceptionCaught(
ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
if (this == ctx.getPipeline().getLast()) {
logger.warn(
"EXCEPTION, please implement " + getClass().getName() +
".exceptionCaught() for proper handling.", e.getCause());
}
ctx.sendUpstream(e);
}