io.netty.channel.socket.nio.AbstractNioChannel doRegister() ？？

[boboyada]

@OverRide
protected void doRegister() throws Exception {.............
selectionKey = javaChannel().register(eventLoop().selector, 0, this);
what does the "opt==0" means ?
1=OP_READ
2=OP_WRITE
8=OP_CONNECT
16=OP_ACCEPT
0=??

but ,I found that:
NioEventLoop.has method :
private static void processSelectedKey(SelectionKey k, AbstractNioChannel ch) {
............
....................
try {
int readyOps = k.readyOps();
if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {
unsafe.read();
if (!ch.isOpen()) {
// Connection already closed - no need to handle write.
return;
}
}
........
"readyOps==0" ,why?

thanks you!

[normanmaurer]

@boboyada I think this is a left over and we could remove it.

@trustin agree ?

[trustin]

It's an intentional stuff to deal with a potential JDK bug where it returns a selection key with readyOps set to 0 for no good reason, leading to a spin loop. So, I'd leave it as it is.

[normanmaurer]

@trustin maybe we could just have a comment here to know later again why we
have it there ?

2013/9/15 Trustin Lee notifications@github.com

It's an intentional stuff to deal with a potential JDK bug where it
returns a selection key with readyOps set to 0 for no good reason, leading
to a spin loop. So, I'd leave it as it is.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/1836#issuecomment-24477435
.

[normanmaurer]

Added a comment to clearify.

[yingchaozyc]

for (;;) {
try {
// 在JDK的channel上注册事件 这块没有理解清楚 TODO 注册的数字值是0 是什么意思？岂不是没有事件接受
selectionKey = javaChannel().register(eventLoop().selector, 0, this);
return;
} catch (CancelledKeyException e) {
if (!selected) {
// Force the Selector to select now as the "canceled" SelectionKey may still be
// cached and not removed because no Select.select(..) operation was called yet.
eventLoop().selectNow();
selected = true;
} else {
// We forced a select operation on the selector before but the SelectionKey is still cached
// for whatever reason. JDK bug ?
throw e;
}
}
}

why set 0 in register method? avoid jdk bug here? version4.0.17.final
I can't understand , it's not a questions with blow code:

if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {

[boboyada]

你好，我很久没有看这个项目了，当时也没有看透。
今天抽空再看了一下。也无法准确回答。这个0注册肯定是不会引起实质性的任何“读”操作的。这种注册只是想判断JDK的selector有没有立刻返回或报错。所以才会在eventloop中有if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {这一判断。
认为注册与绑定，连接是不同的意图。所以在clientboot.connect方法链中，有如下一句
AbstractNioChannel.java
private void fulfillConnectPromise(ChannelPromise promise, boolean wasActive) {
if (!wasActive && isActive()) {
pipeline().fireChannelActive();----》这个方法的实现中，才会出现真正的SelectionKey.OP_READ的注册动作。
}
}

------------------ 原始邮件 ------------------
发件人: "yingchaozyc";notifications@github.com;
发送时间: 2014年5月12日(星期一) 晚上11:49
收件人: "netty/netty"netty@noreply.github.com;
抄送: "ant"287602273@qq.com;
主题: Re: [netty] io.netty.channel.socket.nio.AbstractNioChannel doRegister() ？？ (#1836)

for (;;) {
try {
// 在JDK的channel上注册事件 这块没有理解清楚 TODO 注册的数字值是0 是什么意思？岂不是没有事件接受
selectionKey = javaChannel().register(eventLoop().selector, 0, this);
return;
} catch (CancelledKeyException e) {
if (!selected) {
// Force the Selector to select now as the "canceled" SelectionKey may still be
// cached and not removed because no Select.select(..) operation was called yet.
eventLoop().selectNow();
selected = true;
} else {
// We forced a select operation on the selector before but the SelectionKey is still cached
// for whatever reason. JDK bug ?
throw e;
}
}
}

why set 0 in register method? avoid jdk bug here? version4.0.17.final
I can't understand , it's not a questions with blow code:

if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {

—
Reply to this email directly or view it on GitHub.

[dengyuankai272]

There are two way to register interested events:

1. Channel.register()
2. SelectionKey.interestOps(int)

netty use 2.

After binding channel to selector with interestOps 0, netty will invoke fireChannelActive()
->fire a read event
->HeadContext.unsafe.doBeginRead()
->SelectionKey.interestOps(int)
to set interestOps.

protected void doBeginRead() throws Exception {  
    if (inputShutdown) {  
        return;  
    }  

    final SelectionKey selectionKey = this.selectionKey;  
    if (!selectionKey.isValid()) {  
        return;  
    }  

    final int interestOps = selectionKey.interestOps();  
    if ((interestOps & readInterestOp) == 0) {  
        selectionKey.interestOps(interestOps | readInterestOp);  
    }  
}

[zuoshoulan]

It took me a day to find the place to register “SelectionKey.OP_ACCEPT”，finally，I found that，case 1 eq case 2

        selector = Selector.open();
        serverSocket = ServerSocketChannel.open();
        serverSocket.configureBlocking(false);
//        SelectionKey sk = serverSocket.register(selector, SelectionKey.OP_ACCEPT); // case 1
        SelectionKey sk = serverSocket.register(selector, 0); //case 2
        serverSocket.socket().bind(new InetSocketAddress(port));
        sk.attach(new Acceptor());