NIO使用Reactor模式遇到的问题
2024-08-21 21:19:39
关于Reactor模式，不再多做介绍，推荐Doug Lea大神的教程：Java 可扩展的IO
本来在Reactor的构造方法中完成一系列操作是没有问题的：
public class Reactor implements Runnable {
private final Selector selector;
public Reactor() throws IOException {
selector = Selector.open();
String host = "127.0.0.1";
int port = 12345;
ServerSocketChannel serverChannel = ServerSocketChannel.open();
serverChannel.socket().bind(new InetSocketAddress(host, port));
serverChannel.configureBlocking(false);
serverChannel.register(selector, SelectionKey.OP_ACCEPT, new Acceptor(serverChannel, selector));
}
@Override
public void run() {
while (!Thread.interrupted()) {
try {
selector.select();
Set<SelectionKey> selected = selector.selectedKeys();
Iterator<SelectionKey> it = selected.iterator();
while (it.hasNext()) {
dispatch(it.next());
}
selected.clear();
} catch (IOException e) {
e.printStackTrace();
}
}
}
private void dispatch(SelectionKey next) {
Runnable r = (Runnable) next.attachment();
if (r != null) {
r.run();
}
}
public void registerChannel(SelectableChannel channel, int ops) throws IOException {
if (channel instanceof ServerSocketChannel) {
ServerSocketChannel socketChannel = (ServerSocketChannel) channel;
channel.register(selector, ops, new Acceptor(socketChannel, selector));
}
}
}然而有些参数需要在外层操作，我想这样弄：
public Reactor() throws IOException {
selector = Selector.open();
}
在主线程中启动server [reactorManager.start()来启动Reactor线程]
private void startReactorManager() throws IOException {
reactorManager = new ReactorManager();
reactorManager.start();
}
private void startNIOServer(ServerConfig serverConfig) throws IOException {
String host = serverConfig.getHost();
int port = serverConfig.getTcpPort();
ServerSocketChannel serverChannel = ServerSocketChannel.open();
serverChannel.socket().bind(new InetSocketAddress(host, port));
serverChannel.configureBlocking(false);
reactorManager.registerChannel(serverChannel, SelectionKey.OP_ACCEPT);
}也就是先启动一个线程来Selector.open();然后在主线程中注册通道和事件。
结果一直无法监听到客户端的连接，跟踪才发现服务端的注册方法阻塞了，原因是锁的问题，具体还不清楚。
想一想，既然在构造函数中可以注册，放到main线程中却不行，那么是否我们可以在注册时检查，如果this是当前Reactor线程,就直接注册，这跟在构造函数中没有区别。
如果不是，就放到队列中，当然你这时放了，selector.select()一直阻塞着，你也无法取出来注册，那么我们可以利用selector.wakeup()唤醒它。
新的方案如下：
public class Reactor extends Thread {
private final Selector selector;
private LinkedBlockingQueue<Object[]> register = new LinkedBlockingQueue<>() ;//channel、ops、attach
private final AtomicBoolean wakeup = new AtomicBoolean() ;
public Reactor() throws IOException {
selector = Selector.open();
}
@Override
public void run() {
while (!Thread.interrupted()) {
try {
wakeup.set(false);
processRegister();
selector.select();
Set<SelectionKey> selected = selector.selectedKeys();
Iterator<SelectionKey> it = selected.iterator();
while (it.hasNext()) {
dispatch(it.next());
}
selected.clear();
} catch (IOException e) {
e.printStackTrace();
}
}
}
private void processRegister() {
Object[] object;
while ((object = this.register.poll()) != null) {
try {
SelectableChannel channel = (SelectableChannel) object[0];
if (!channel.isOpen())
continue;
int ops = ((Integer) object[1]).intValue();
Object attachment = object[2];
channel.register(this.selector, ops, attachment);
} catch (Exception e) {
e.printStackTrace();
}
}
}
private void dispatch(SelectionKey next) {
Runnable r = (Runnable) next.attachment();
if (r != null) {
r.run();
}
}
public void registerChannel(SelectableChannel channel, int ops) throws IOException {
ServerSocketChannel serverChannel = null;
if (channel instanceof ServerSocketChannel) {
serverChannel = (ServerSocketChannel) channel;
}
Object attachment = new Acceptor(serverChannel, selector);
if (this == Thread.currentThread()) {
serverChannel.register(selector, ops, attachment);
} else {
this.register.offer(new Object[]{ channel, ops, attachment });
if (wakeup.compareAndSet(false, true)) {
this.selector.wakeup();
}
}
}
}这样就解决了问题，在此记录下！
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