Netty空闲检测之写空闲

// 源码位置: io.netty.handler.timeout.IdleStateHandler#write


@Override
public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
    if (writerIdleTimeNanos > 0 || allIdleTimeNanos > 0) {
        // 业务线程在执行写入的时候,最终会将写操作封装成一个写任务放入IO线程的队列中.同时它会设置一个监听,用于回调使用. 
        ctx.write(msg, promise.unvoid()).addListener(writeListener);
    } else {
        ctx.write(msg, promise);
    }
}


private final ChannelFutureListener writeListener = new ChannelFutureListener() {
    @Override
    public void operationComplete(ChannelFuture future) throws Exception {
        lastWriteTime = ticksInNanos();
        firstWriterIdleEvent = firstAllIdleEvent = true;
    }
};

// 源码位置: io.netty.handler.timeout.IdleStateHandler.WriterIdleTimeoutTask
private final class WriterIdleTimeoutTask extends AbstractIdleTask {


    WriterIdleTimeoutTask(ChannelHandlerContext ctx) {
        super(ctx);
    }


    @Override
    protected void run(ChannelHandlerContext ctx) {
        long lastWriteTime = IdleStateHandler.this.lastWriteTime;
        
        long nextDelay = writerIdleTimeNanos - (ticksInNanos() - lastWriteTime);
        
        if (nextDelay <= 0) {
            writerIdleTimeout = schedule(ctx, this, writerIdleTimeNanos, TimeUnit.NANOSECONDS);


            boolean first = firstWriterIdleEvent;
            firstWriterIdleEvent = false;


            try {
                // 这个地方就是用于是否考虑写操作慢的情况
                if (hasOutputChanged(ctx, first)) {
                    return;
                }


                IdleStateEvent event = newIdleStateEvent(IdleState.WRITER_IDLE, first);
                channelIdle(ctx, event);
            } catch (Throwable t) {
                ctx.fireExceptionCaught(t);
            }
        } else {
            writerIdleTimeout = schedule(ctx, this, nextDelay, TimeUnit.NANOSECONDS);
        }
    }
}