在线程池中寻找堆栈

在线程池中寻找堆栈

下面看一个简单的例子:

public class DivTask implements Runnable {

    int a, b;

    public DivTask(int a, int b) {
        this.a = a;
        this.b = b;
    }

    @Override
    public void run() {
        double re = a / b;
        System.out.println(re);
    }
}

运行该任务:

    public static void main(String[] args) {
        ThreadPoolExecutor pools = new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                0L, TimeUnit.SECONDS,
                new SynchronousQueue<Runnable>());

        for (int i = 0; i < 5; i++) {
            pools.submit(new DivTask(100, i));
        }
    }

可以得到:

100.0
25.0
33.0
50.0

只有4个输出,也就是说程序漏算了一组数据,并且程序没有任何日志,没有任何错误提示.

解决上述问题最简单的一种方法就输出放弃submit(),改用execute()

pools.execute(new DivTask(100, i));

或者使用

Future  submit = pools.submit(new DivTask(100, i));
submit.get();

上面两种方法都可以得到部分堆栈信息,如下所示:

Exception in thread "pool-1-thread-1" java.lang.ArithmeticException: / by zero
	at threadDemo.DivTask.run(DivTask.java:19)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
100.0
25.0
33.0
50.0

这里只能知道异常是在哪里抛的,并不知道是在哪里提交的,所以我们扩展我们的ThreadPoolExecutor线程池

/**
 * @author luozhiyun on 2018/6/25.
 */
public class TraceThreadPoolExecutor extends ThreadPoolExecutor {
    public TraceThreadPoolExecutor(int corePoolSize, int maximumPoolSize,
                                   long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
    }

    @Override
    public void execute(Runnable command) {
        super.execute(wrap(command,clientTrace(),Thread.currentThread().getName()));
    }

    @Override
    public Future<?> submit(Runnable task) {
        return super.submit(wrap(task, clientTrace(), Thread.currentThread().getName()));
    }

    private Exception clientTrace() {
        return new Exception("Client stack trace");
    }

    private Runnable wrap(final Runnable task, final Exception clientStack, String clientThreadName) {
        return new Runnable() {
            @Override
            public void run() {
                try {
                    task.run();
                } catch (Exception e) {
                    clientStack.printStackTrace();
                    throw e;
                }
            }
        };
    }

    public static void main(String[] args) {
        ThreadPoolExecutor pools = new TraceThreadPoolExecutor(0, Integer.MAX_VALUE,
                0L, TimeUnit.SECONDS,
                new SynchronousQueue<Runnable>());

        for (int i = 0; i < 5; i++) {
            pools.execute(new DivTask(100, i));
        }
    }
}

通过上面扩展的线程池, 就可以打印出堆栈信息了

100.0
25.0
33.0
50.0
java.lang.Exception: Client stack trace
	at threadDemo.TraceThreadPoolExecutor.clientTrace(TraceThreadPoolExecutor.java:25)
	at threadDemo.TraceThreadPoolExecutor.execute(TraceThreadPoolExecutor.java:16)
	at threadDemo.TraceThreadPoolExecutor.main(TraceThreadPoolExecutor.java:48)
Exception in thread "pool-1-thread-1" java.lang.ArithmeticException: / by zero
	at threadDemo.DivTask.run(DivTask.java:19)
	at threadDemo.TraceThreadPoolExecutor$1.run(TraceThreadPoolExecutor.java:33)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

Process finished with exit code 0

现在我们不仅可以得到异常发生的Runnable实现内的信息,我们也知道了这个任务是在哪里提交的.