Python 官方文档:入门教程 => 点击学习
目录1、两阶段终止模式介绍2、Terminator代码演示3、TerminationRequester4、模拟客户端或者服务端都可能终止服务的例子 5、Mac telnet模拟客户端
有时候,我们希望提前结束线程,但安全可靠地停止线程,并不是一件容易的事情,如果立即停止线程,会使共享的数据结构处于不一致的状态,如目前已经废弃使用的Thread类的stop方法(它会使线程在抛出java.lang.ThreadDeath
之后终止线程,即使是在执行synchronized
方法的时候)。更好的做法是执行完终止处理,再终止线程,即Two-phase Termination
,两阶段终止模式。
该模式有两个角色:
Terminator
,终止者,负责接收终止请求,执行终止处理,处理完成后再终止自己。TerminationRequester
:终止请求发出者,用来向Terminator
发出终止请求。该模式示例代码如下:
public class CounterIncrement extends Thread {
private volatile boolean terminated = false;
private int counter = 0;
private Random random = new Random(System.currentTimeMillis());
@Override
public void run() {
try {
while (!terminated) {
System.out.println(Thread.currentThread().getName()+" "+counter++);
Thread.sleep(random.nextInt(1000));
}
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
this.clean();
}
}
private void clean() {
System.out.println("do some clean work for the second phase,current counter "+counter);
}
public void close() {
this.terminated = true;
this.interrupt();
}
}
public class CounterTest {
public static void main(String[] args) throws InterruptedException {
CounterIncrement counterIncrement = new CounterIncrement();
counterIncrement.start();
Thread.sleep(15_000L);
//主动清理
counterIncrement.close();
}
}
这段代码可以看出实现两阶段终止模式必须注意的是:
使用线程停止标志和interrupt
方法,两者缺一不可
public void close() {
this.terminated = true;
this.interrupt();
}
这里使用了terminated
作为线程停止标志,变量采用volatile
修饰,避免了使用显式锁的开销,又保证了内存可见性。线程run
方法会检查terminated
属性,如果属性为true
,就停止线程,但线程可能调用了阻塞方法,处于wait
状态,任务也就可能永远不会检查terminated
标志;线程也有可能处于sleep()
状态,等sleep
时间过后再执行终止状态,程序的响应性就下降了。你可以把方法改成如下运行,线程停止明显变慢了许多:
public void close() {
terminated = true;
}
public class AppServer extends Thread {
private static final int DEFAULT_PORT = 12722;
private final static ExecutorService executor = Executors.newFixedThreadPool(10);
private int port;
private volatile boolean start = true;
private List<ClientHandler> clientHandlers = new ArrayList<>();
private ServerSocket server;
public AppServer() {
this(DEFAULT_PORT);
}
public AppServer(int port) {
this.port = port;
}
@Override
public void run() {
try {
server = new ServerSocket(port);
while (start) {
Socket client = server.accept();
ClientHandler clientHandler = new ClientHandler(client);
executor.submit(clientHandler);
this.clientHandlers.add(clientHandler);
}
} catch (IOException e) {
//throw new RuntimeException();
} finally {
this.dispose();
}
}
public void dispose() {
System.out.println("dispose");
this.clientHandlers.stream().forEach(ClientHandler::stop);
this.executor.shutdown();
}
public void shutdown() throws IOException {
this.start = false;
this.interrupt();
this.server.close();
}
}
public class ClientHandler implements Runnable {
private final Socket socket;
private volatile boolean running = true;
public ClientHandler(Socket socket) {
this.socket = socket;
}
@Override
public void run() {
try (InputStream inputStream = socket.getInputStream();
OutputStream outputStream = socket.getOutputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(inputStream));
PrintWriter printWriter = new PrintWriter(outputStream)) {
while (running) {
String message = br.readLine();
if (message == null) {
break;
}
System.out.println("Come from client >" + message);
printWriter.write("echo " + message+"\n");
printWriter.flush();
}
} catch (IOException e) {
//自动关闭的时候 将running
this.running = false;
}finally {
this.stop();
}
}
public void stop() {
if (!running) {
return;
}
this.running = false;
try {
this.socket.close();
} catch (IOException e) {
}
}
}
public class AppServerClient {
public static void main(String[] args) throws InterruptedException, IOException {
AppServer server = new AppServer(12135);
server.start();
Thread.sleep(20_000L);
server.shutdown();
}
}
boGon:~ kpioneer$ telnet localhost 12135
Trying ::1...
Connected to localhost.
Escape character is '^]'.
hello
echo hello
I love you
echo I love you
Connection closed by foreign host.
服务端输出:
Come from client >hello
Come from client >I love you
dispose
总结:
可以看到,在子类使用两阶段终止模式时,其只需要实现各自所需要执行的任务,并且更新当前任务的数量即可。在某些情况下,当前任务的数量也可以不进行更新,比如在进行终止时,不关心当前剩余多少任务需要执行。
到此这篇关于Java多线程 两阶段终止模式Two-Phase Termination Patter
的文章就介绍到这了,更多相关Java多线程 两阶段终止模式内容请搜索编程网以前的文章或继续浏览下面的相关文章希望大家以后多多支持编程网!
--结束END--
本文标题: Java多线程 两阶段终止模式Two-Phase Termination Patter
本文链接: https://www.lsjlt.com/news/155780.html(转载时请注明来源链接)
有问题或投稿请发送至: 邮箱/279061341@qq.com QQ/279061341
2024-03-01
2024-03-01
2024-03-01
2024-02-29
2024-02-29
2024-02-29
2024-02-29
2024-02-29
2024-02-29
2024-02-29
回答
回答
回答
回答
回答
回答
回答
回答
回答
回答
0