为什么在Netty用户指南中调用ctx.write()之后没有调用ctx.flush()?

问题描述

在netty Java文档中说so be sure to call flush() once you want to request to flush，但是在此示例中说没有必要调用ctx.flush().但是我没有发现flush(ChannelHandlerContext ctx)像它所说的那样.

In the netty Java document says that so be sure to call flush() once you want to request to flush, but in this example it says that there is no need to call ctx.flush(). But I did not find flush(ChannelHandlerContext ctx) was called as what it said.

package io.netty.example.time;

public class TimeEncoder extends ChannelOutboundHandlerAdapter {
    @Override
    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
        UnixTime m = (UnixTime) msg;
        ByteBuf encoded = ctx.alloc().buffer(4);
        encoded.writeInt((int)m.value());
        ctx.write(encoded, promise); // (1)
    }
}

Second, we did not call ctx.flush(). There is a separate handler method void flush(ChannelHandlerContext ctx) which is purposed to override the flush() operation. https://netty.io/wiki/user-guide-for-4.x.html#wiki-h3-8

Second, we did not call ctx.flush(). There is a separate handler method void flush(ChannelHandlerContext ctx) which is purposed to override the flush() operation.https://netty.io/wiki/user-guide-for-4.x.html#wiki-h3-8

推荐答案

缓冲的要点是，您可以将一堆"数据聚集"在一起并一次发送，因为发送大量数据的速度大致一样快因为要发送少量数据(因为IO速度很慢).

The point of buffering is that you "gather" a bunch of data together and send it all at once, because it's roughly as fast to send a lot of data as it is to send a small amount of data (because IO is slow).

这正在分配一个4字节的缓冲区.如果每4个字节刷新一次，那将不是很有效.

This is allocating a 4-byte buffer. If you flushed every 4 bytes, it wouldn't be very efficient.

在某处会有冲洗，只是不是以这种特定方法进行的.

There will be a flush, somewhere, just not in this particular method.

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