reactor模式：主从式reactor

前面两篇文章提到

NIO的server模式只有5个阶段，但是，NIO的selectionkey里确实有个accept事件，所以，为了区别，衍生出了主reactor和从reactor

并且，从reactor可以根据服务器的负荷，新增多个从reactor进行请求处理

服务器架构如下图

这个就是完整版的reactor模式的架构图了，目前使用到了reactor模式的框架（如netty），基本用的模式就是这个

代码实现：

 1  // Reactor線程  
 2     package server;  
 3       
 4     import java.io.IOException;  
 5     import java.net.InetSocketAddress;  
 6     import java.nio.channels.SelectionKey;  
 7     import java.nio.channels.Selector;  
 8     import java.nio.channels.ServerSocketChannel;  
 9     import java.util.Iterator;  
10     import java.util.Set;  
11       
12     public class TCPReactor implements Runnable {  
13       
14         private final ServerSocketChannel ssc;  
15         private final Selector selector; // mainReactor用的selector  
16       
17         public TCPReactor(int port) throws IOException {  
18             selector = Selector.open();  
19             ssc = ServerSocketChannel.open();  
20             InetSocketAddress addr = new InetSocketAddress(port);  
21             ssc.socket().bind(addr); // 在ServerSocketChannel綁定監聽端口  
22             ssc.configureBlocking(false); // 設置ServerSocketChannel為非阻塞  
23             SelectionKey sk = ssc.register(selector, SelectionKey.OP_ACCEPT); // ServerSocketChannel向selector註冊一個OP_ACCEPT事件，然後返回該通道的key  
24             sk.attach(new Acceptor(ssc)); // 給定key一個附加的Acceptor對象  
25         }  
26       
27         @Override  
28         public void run() {  
29             while (!Thread.interrupted()) { // 在線程被中斷前持續運行  
30                 System.out.println("mainReactor waiting for new event on port: "  
31                         + ssc.socket().getLocalPort() + "...");  
32                 try {  
33                     if (selector.select() == 0) // 若沒有事件就緒則不往下執行  
34                         continue;  
35                 } catch (IOException e) {  
36                     e.printStackTrace();  
37                 }  
38                 Set<SelectionKey> selectedKeys = selector.selectedKeys(); // 取得所有已就緒事件的key集合  
39                 Iterator<SelectionKey> it = selectedKeys.iterator();  
40                 while (it.hasNext()) {  
41                     dispatch((SelectionKey) (it.next())); // 根據事件的key進行調度  
42                     it.remove();  
43                 }  
44             }  
45         }  
46       
47         /* 
48          * name: dispatch(SelectionKey key) 
49          * description: 調度方法，根據事件綁定的對象開新線程 
50          */  
51         private void dispatch(SelectionKey key) {  
52             Runnable r = (Runnable) (key.attachment()); // 根據事件之key綁定的對象開新線程  
53             if (r != null)  
54                 r.run();  
55         }  
56       
57     }

 1  // 接受連線請求線程  
 2     package server;  
 3       
 4     import java.io.IOException;  
 5     import java.nio.channels.SelectionKey;  
 6     import java.nio.channels.Selector;  
 7     import java.nio.channels.ServerSocketChannel;  
 8     import java.nio.channels.SocketChannel;  
 9       
10     public class Acceptor implements Runnable {  
11       
12         private final ServerSocketChannel ssc; // mainReactor監聽的socket通道  
13         private final int cores = Runtime.getRuntime().availableProcessors(); // 取得CPU核心數  
14         private final Selector[] selectors = new Selector[cores]; // 創建核心數個selector給subReactor用  
15         private int selIdx = 0; // 當前可使用的subReactor索引  
16         private TCPSubReactor[] r = new TCPSubReactor[cores]; // subReactor線程  
17         private Thread[] t = new Thread[cores]; // subReactor線程  
18       
19         public Acceptor(ServerSocketChannel ssc) throws IOException {  
20             this.ssc = ssc;  
21             // 創建多個selector以及多個subReactor線程  
22             for (int i = 0; i < cores; i++) {  
23                 selectors[i] = Selector.open();  
24                 r[i] = new TCPSubReactor(selectors[i], ssc, i);  
25                 t[i] = new Thread(r[i]);  
26                 t[i].start();  
27             }  
28         }  
29       
30         @Override  
31         public synchronized void run() {  
32             try {  
33                 SocketChannel sc = ssc.accept(); // 接受client連線請求  
34                 System.out.println(sc.socket().getRemoteSocketAddress().toString()  
35                         + " is connected.");  
36       
37                 if (sc != null) {  
38                     sc.configureBlocking(false); // 設置為非阻塞  
39                     r[selIdx].setRestart(true); // 暫停線程  
40                     selectors[selIdx].wakeup(); // 使一個阻塞住的selector操作立即返回  
41                     SelectionKey sk = sc.register(selectors[selIdx],  
42                             SelectionKey.OP_READ); // SocketChannel向selector[selIdx]註冊一個OP_READ事件，然後返回該通道的key  
43                     selectors[selIdx].wakeup(); // 使一個阻塞住的selector操作立即返回  
44                     r[selIdx].setRestart(false); // 重啟線程  
45                     sk.attach(new TCPHandler(sk, sc)); // 給定key一個附加的TCPHandler對象  
46                     if (++selIdx == selectors.length)  
47                         selIdx = 0;  
48                 }  
49             } catch (IOException e) {  
50                 e.printStackTrace();  
51             }  
52         }  
53       
54     }

 1  package server;  
 2       
 3     import java.io.IOException;  
 4     import java.nio.channels.SelectionKey;  
 5     import java.nio.channels.Selector;  
 6     import java.nio.channels.ServerSocketChannel;  
 7     import java.util.Iterator;  
 8     import java.util.Set;  
 9       
10     public class TCPSubReactor implements Runnable {  
11       
12         private final ServerSocketChannel ssc;  
13         private final Selector selector;  
14         private boolean restart = false;  
15         int num;  
16       
17         public TCPSubReactor(Selector selector, ServerSocketChannel ssc, int num) {  
18             this.ssc = ssc;  
19             this.selector = selector;  
20             this.num = num;  
21         }  
22       
23         @Override  
24         public void run() {  
25             while (!Thread.interrupted()) { // 在線程被中斷前持續運行  
26                 //System.out.println("ID:" + num  
27                 //      + " subReactor waiting for new event on port: "  
28                 //      + ssc.socket().getLocalPort() + "...");  
29                 System.out.println("waiting for restart");  
30                 while (!Thread.interrupted() && !restart) { // 在線程被中斷前以及被指定重啟前持續運行  
31                     try {  
32                         if (selector.select() == 0)  
33                             continue; // 若沒有事件就緒則不往下執行  
34                     } catch (IOException e) {  
35                         e.printStackTrace();  
36                     }  
37                     Set<SelectionKey> selectedKeys = selector.selectedKeys(); // 取得所有已就緒事件的key集合  
38                     Iterator<SelectionKey> it = selectedKeys.iterator();  
39                     while (it.hasNext()) {  
40                         dispatch((SelectionKey) (it.next())); // 根據事件的key進行調度  
41                         it.remove();  
42                     }  
43                 }  
44             }  
45         }  
46       
47         /* 
48          * name: dispatch(SelectionKey key) description: 調度方法，根據事件綁定的對象開新線程 
49          */  
50         private void dispatch(SelectionKey key) {  
51             Runnable r = (Runnable) (key.attachment()); // 根據事件之key綁定的對象開新線程  
52             if (r != null)  
53                 r.run();  
54         }  
55       
56         public void setRestart(boolean restart) {  
57             this.restart = restart;  
58         }  
59     }

 1   // Handler線程  
 2     package server;  
 3       
 4     import java.io.IOException;  
 5     import java.nio.channels.SelectionKey;  
 6     import java.nio.channels.SocketChannel;  
 7     import java.util.concurrent.LinkedBlockingQueue;  
 8     import java.util.concurrent.ThreadPoolExecutor;  
 9     import java.util.concurrent.TimeUnit;  
10       
11     public class TCPHandler implements Runnable {  
12       
13         private final SelectionKey sk;  
14         private final SocketChannel sc;  
15         private static final int THREAD_COUNTING = 10;  
16         private static ThreadPoolExecutor pool = new ThreadPoolExecutor(  
17                 THREAD_COUNTING, THREAD_COUNTING, 10, TimeUnit.SECONDS,  
18                 new LinkedBlockingQueue<Runnable>()); // 線程池  
19       
20         HandlerState state; // 以狀態模式實現Handler  
21       
22         public TCPHandler(SelectionKey sk, SocketChannel sc) {  
23             this.sk = sk;  
24             this.sc = sc;  
25             state = new ReadState(); // 初始狀態設定為READING  
26             pool.setMaximumPoolSize(32); // 設置線程池最大線程數  
27         }  
28       
29         @Override  
30         public void run() {  
31             try {  
32                 state.handle(this, sk, sc, pool);  
33       
34             } catch (IOException e) {  
35                 System.out.println("[Warning!] A client has been closed.");  
36                 closeChannel();  
37             }  
38         }  
39       
40         public void closeChannel() {  
41             try {  
42                 sk.cancel();  
43                 sc.close();  
44             } catch (IOException e1) {  
45                 e1.printStackTrace();  
46             }  
47         }  
48       
49         public void setState(HandlerState state) {  
50             this.state = state;  
51         }  
52     }

 1  package server;  
 2       
 3     import java.io.IOException;  
 4     import java.nio.channels.SelectionKey;  
 5     import java.nio.channels.SocketChannel;  
 6     import java.util.concurrent.ThreadPoolExecutor;  
 7       
 8     public interface HandlerState {  
 9       
10         public void changeState(TCPHandler h);  
11       
12         public void handle(TCPHandler h, SelectionKey sk, SocketChannel sc,  
13                 ThreadPoolExecutor pool) throws IOException ;  
14     }

package server;  
      
    import java.io.IOException;  
    import java.nio.ByteBuffer;  
    import java.nio.channels.SelectionKey;  
    import java.nio.channels.SocketChannel;  
    import java.util.concurrent.ThreadPoolExecutor;  
      
    public class ReadState implements HandlerState{  
      
        private SelectionKey sk;  
          
        public ReadState() {  
        }  
          
        @Override  
        public void changeState(TCPHandler h) {  
            // TODO Auto-generated method stub  
            h.setState(new WorkState());  
        }  
      
        @Override  
        public void handle(TCPHandler h, SelectionKey sk, SocketChannel sc,  
                ThreadPoolExecutor pool) throws IOException { // read()  
            this.sk = sk;  
            // non-blocking下不可用Readers，因為Readers不支援non-blocking  
            byte[] arr = new byte[1024];  
            ByteBuffer buf = ByteBuffer.wrap(arr);  
              
            int numBytes = sc.read(buf); // 讀取字符串  
            if(numBytes == -1)  
            {  
                System.out.println("[Warning!] A client has been closed.");  
                h.closeChannel();  
                return;  
            }  
            String str = new String(arr); // 將讀取到的byte內容轉為字符串型態  
            if ((str != null) && !str.equals(" ")) {  
                h.setState(new WorkState()); // 改變狀態(READING->WORKING)  
                pool.execute(new WorkerThread(h, str)); // do process in worker thread  
                System.out.println(sc.socket().getRemoteSocketAddress().toString()  
                        + " > " + str);  
            }  
              
        }  
          
        /* 
         * 執行邏輯處理之函數 
         */  
        synchronized void process(TCPHandler h, String str) {  
            // do process(decode, logically process, encode)..  
            // ..  
            h.setState(new WriteState()); // 改變狀態(WORKING->SENDING)  
            this.sk.interestOps(SelectionKey.OP_WRITE); // 通過key改變通道註冊的事件  
            this.sk.selector().wakeup(); // 使一個阻塞住的selector操作立即返回  
        }  
      
        /* 
         * 工作者線程 
         */  
        class WorkerThread implements Runnable {  
      
            TCPHandler h;  
            String str;  
      
            public WorkerThread(TCPHandler h, String str) {  
                this.h = h;  
                this.str=str;  
            }  
      
            @Override  
            public void run() {  
                process(h, str);  
            }  
      
        }  
    }

 1  package server;  
 2       
 3     import java.io.IOException;  
 4     import java.nio.channels.SelectionKey;  
 5     import java.nio.channels.SocketChannel;  
 6     import java.util.concurrent.ThreadPoolExecutor;  
 7       
 8     public class WorkState implements HandlerState {  
 9       
10         public WorkState() {  
11         }  
12           
13         @Override  
14         public void changeState(TCPHandler h) {  
15             // TODO Auto-generated method stub  
16             h.setState(new WriteState());  
17         }  
18       
19         @Override  
20         public void handle(TCPHandler h, SelectionKey sk, SocketChannel sc,  
21                 ThreadPoolExecutor pool) throws IOException {  
22             // TODO Auto-generated method stub  
23               
24         }  
25       
26     }

 package server;  
      
    import java.io.IOException;  
    import java.nio.ByteBuffer;  
    import java.nio.channels.SelectionKey;  
    import java.nio.channels.SocketChannel;  
    import java.util.concurrent.ThreadPoolExecutor;  
      
    public class WriteState implements HandlerState{  
      
        public WriteState() {  
        }  
          
        @Override  
        public void changeState(TCPHandler h) {  
            // TODO Auto-generated method stub  
            h.setState(new ReadState());  
        }  
      
        @Override  
        public void handle(TCPHandler h, SelectionKey sk, SocketChannel sc,  
                ThreadPoolExecutor pool) throws IOException { // send()  
            // get message from message queue  
              
            String str = "Your message has sent to "  
                    + sc.socket().getLocalSocketAddress().toString() + "
";  
            ByteBuffer buf = ByteBuffer.wrap(str.getBytes()); // wrap自動把buf的position設為0，所以不需要再flip()  
      
            while (buf.hasRemaining()) {  
                sc.write(buf); // 回傳給client回應字符串，發送buf的position位置 到limit位置為止之間的內容  
            }  
              
            h.setState(new ReadState()); // 改變狀態(SENDING->READING)  
            sk.interestOps(SelectionKey.OP_READ); // 通過key改變通道註冊的事件  
            sk.selector().wakeup(); // 使一個阻塞住的selector操作立即返回  
        }  
    }

 1 package server;  
 2       
 3     import java.io.IOException;  
 4       
 5     public class Main {  
 6       
 7           
 8         public static void main(String[] args) {  
 9             // TODO Auto-generated method stub  
10             try {  
11                 TCPReactor reactor = new TCPReactor(1333);  
12                 new Thread(reactor).start();  
13             } catch (IOException e) {  
14                 // TODO Auto-generated catch block  
15                 e.printStackTrace();  
16             }  
17         }  
18       
19     }

总的来说，主从式reactor比多线程的reactor先进的地方在于：

1.主reactor是一个线程，负责监听外部的连线请求，并派发给Acceptor处理。故Main Reactor中的selector只有注册OP_ACCEPT事件，也只能监听OP_ACCEPT事件。

而处理请求是其他N个不同的线程，即从reactor

2.可以根据请求的密集度来调控从reactor的个数

参考文章：

https://blog.csdn.net/yehjordan/article/details/51026045

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原文地址：https://www.cnblogs.com/billmiao/p/9872220.html