NIO的多线程优化

单线程会浪费多核的优势

单线程如果在某一业务上花费时间过长，会影响其他业务的处理

boss负责连接，worker负责读写

服务端代码：

package com.netty.demo;import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicInteger;import static com.netty.demo.ByteBufferUtil.debugAll;public class ThreadsServer {public static void main(String[] args) {try (ServerSocketChannel server = ServerSocketChannel.open()) {// 当前线程为Boss线程Thread.currentThread().setName("Boss");server.bind(new InetSocketAddress(8080));// 负责轮询Accept事件的SelectorSelector boss = Selector.open();server.configureBlocking(false);server.register(boss, SelectionKey.OP_ACCEPT);// 创建固定数量的WorkerWorker[] workers = new Worker[4];// 用于负载均衡的原子整数AtomicInteger robin = new AtomicInteger(0);for(int i = 0; i < workers.length; i++) {workers[i] = new Worker("worker-"+i);}while (true) {boss.select();Set<SelectionKey> selectionKeys = boss.selectedKeys();Iterator<SelectionKey> iterator = selectionKeys.iterator();while (iterator.hasNext()) {SelectionKey key = iterator.next();iterator.remove();// BossSelector负责Accept事件if (key.isAcceptable()) {// 建立连接SocketChannel socket = server.accept();System.out.println("connected...");socket.configureBlocking(false);// socket注册到Worker的Selector中System.out.println("before read...");// 负载均衡，轮询分配Workerworkers[robin.getAndIncrement()% workers.length].register(socket);System.out.println("after read...");}}}} catch (IOException e) {e.printStackTrace();}}static class Worker implements Runnable {private Thread thread;private volatile Selector selector;private String name;private volatile boolean started = false;/*** 同步队列，用于Boss线程与Worker线程之间的通信*/private ConcurrentLinkedQueue<Runnable> queue;public Worker(String name) {this.name = name;}public void register(final SocketChannel socket) throws IOException {// 只启动一次if (!started) {thread = new Thread(this, name);selector = Selector.open();queue = new ConcurrentLinkedQueue<>();thread.start();started = true;}// 向同步队列中添加SocketChannel的注册事件// 在Worker线程中执行注册事件queue.add(new Runnable() {@Overridepublic void run() {try {socket.register(selector, SelectionKey.OP_READ);} catch (IOException e) {e.printStackTrace();}}});// 唤醒被阻塞的Selector// select类似LockSupport中的park，wakeup的原理类似LockSupport中的unparkselector.wakeup();}@Overridepublic void run() {while (true) {try {selector.select();// 通过同步队列获得任务并运行Runnable task = queue.poll();if (task != null) {// 获得任务，执行注册操作task.run();}Set<SelectionKey> selectionKeys = selector.selectedKeys();Iterator<SelectionKey> iterator = selectionKeys.iterator();while(iterator.hasNext()) {SelectionKey key = iterator.next();iterator.remove();// Worker只负责Read事件if (key.isReadable()) {// 简化处理，省略细节SocketChannel socket = (SocketChannel) key.channel();ByteBuffer buffer = ByteBuffer.allocate(16);socket.read(buffer);buffer.flip();ByteBufferUtil.debugAll(buffer);}}} catch (IOException e) {e.printStackTrace();}}}}
}

客户端代码：

package com.netty.demo;import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;public class TestClient {public static void main(String[] args) throws IOException{SocketChannel sc = SocketChannel.open();sc.connect(new InetSocketAddress("localhost",8080));sc.write(Charset.defaultCharset().encode("1234567890abcdef"));System.in.read();}
}

一般worker的数量设置为cpu的核心数比较合适

阻塞I/O模型