java 线程抛出 RuntimeException - 对线程池的影响
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Threads throwing RuntimeException - Impact on Threadpool
提问by R Kaja Mohideen
I just read this articleand thought that threadpool may run out of worker threads if the Runnable's throw exception and exit. I did a small code and checked, but the poolsize didn't vary.
我刚刚读了这篇文章，认为如果Runnable抛出异常并退出，线程池可能会耗尽工作线程。我做了一个小代码并检查，但池大小没有变化。
public class ThreadPoolTest {
public static void main(String[] args) throws InterruptedException {
ThreadPoolExecutor tp = new ThreadPoolExecutor(1, 1, 5, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(1));
Thread.sleep(1000);
System.out.println(tp.getPoolSize());
tp.execute(new Runnable(){
@Override
public void run() {
System.out.println("Executing & Throwing");
throw new NullPointerException();
}
});
Thread.sleep(1000);
System.out.println(tp.getPoolSize());
tp.execute(new Runnable(){
@Override
public void run() {
System.out.println("Executing & Throwing");
throw new NullPointerException();
}
});
Thread.sleep(1000);
System.out.println(tp.getPoolSize());
tp.shutdown();
}
}
}
Output I got was
我得到的输出是
0
Exception in thread "pool-1-thread-1" java.lang.NullPointerException
at threads.ThreadPoolTest.run(ThreadPoolTest.java:18)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Executing & Throwing
1
Exception in thread "pool-1-thread-2" java.lang.NullPointerException
at threads.ThreadPoolTest.run(ThreadPoolTest.java:29)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Executing & Throwing
1
This is on Java 7. Is there any java Threadpool implementation which is vulnerable as stated in the article?
这是在 Java 7 上。是否有文章中所述的易受攻击的 Java 线程池实现？
采纳答案by Brian Agnew
Reading the article, the gist is that a poorly written thread pool can suffer from this problem. In fact, any application that creates a thread and doesn't/can't handle an uncaught exception from that thread.
阅读这篇文章，要点是写得不好的线程池可能会遇到这个问题。事实上，任何创建线程但不/不能处理来自该线程的未捕获异常的应用程序。
I'd expect any reputable source of a thread pool to handle this scenario in some fashion. By reputable, I would include the Oracle-sourced solutions. I suspect if someone was hand-coding a thread pool and they lacked experience then they'd write a less-robust solution.
我希望线程池的任何有信誉的来源都能以某种方式处理这种情况。有信誉的，我会包括来自 Oracle 的解决方案。我怀疑如果有人手动编码线程池并且他们缺乏经验，那么他们会编写一个不太可靠的解决方案。
回答by assylias
The article states:
文章指出：
The standard thread pools allow an uncaught task exception to terminate the pool thread
标准线程池允许未捕获的任务异常终止池线程
which is the case. A slightly amended version of your code shows that the ThreadPool will create a new thread when the previous has died due to an exception.
情况就是这样。对您的代码稍作修改的版本显示，当前一个线程因异常而死亡时，ThreadPool 将创建一个新线程。
As a side comment, you would in general use the submitmethod, and try to geton the returned Future to see if an exception has be thrown.
作为旁注，您通常会使用该submit方法，并尝试get在返回的 Future 上查看是否已抛出异常。
Output:
输出：
0
Creating new thread
Executing & Throwing
Creating new thread
Exception in thread "Thread-0" java.lang.NullPointerException
at javaapplication4.Test2.run(Test2.java:47)
....
1
Executing & Throwing
Creating new thread
Exception in thread "Thread-1" java.lang.NullPointerException
at javaapplication4.Test2.run(Test2.java:56)
....
1
Code:
代码：
public static void main(String[] args) throws InterruptedException {
ThreadPoolExecutor tp = new ThreadPoolExecutor(1, 1, 5, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(1), new ThreadFactory() {
@Override
public Thread newThread(Runnable r) {
System.out.println("Creating new thread");
return new Thread(r);
}
});
Thread.sleep(1000);
System.out.println(tp.getPoolSize());
tp.execute(new Runnable() {
@Override
public void run() {
System.out.println("Executing & Throwing");
throw new NullPointerException();
}
});
Thread.sleep(100);
System.out.println(tp.getPoolSize());
tp.execute(new Runnable() {
@Override
public void run() {
System.out.println("Executing & Throwing");
throw new NullPointerException();
}
});
Thread.sleep(100);
System.out.println(tp.getPoolSize());
tp.shutdown();
}
