Question

我正在调查tomcat关闭进程的奇怪问题：在runnig shutdown.sh之后，java进程仍然出现（我使用ps -ef|grep tomcat检查）情况有点复杂，因为我限制了对服务器的访问（例如，没有调试）

我使用远程kill -3 <PID>和Hotspot功能进行了线程转储（使用jConsole）和堆转储。

在查看线程转储之后，我发现了这个：

"pool-2-thread-1" #74 prio=5 os_prio=0 tid=0x00007f3354359800 nid=0x7b46 waiting on condition [0x00007f333e55d000]
  java.lang.Thread.State: WAITING (parking)
       at sun.misc.Unsafe.park(Native Method)
       - parking to wait for  <0x00000000c378d330> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
       at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
       at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
       at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1081)
       at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)
       at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
       at java.lang.Thread.run(Thread.java:748)

所以，我对问题的理解如下：CachedThreadpool中有一个资源（数据库连接或其他东西），此资源现已被锁定，并阻止线程pool-2-thread-1停止。假设这个线程不是deamon - JVM无法正常停止。

有没有办法找出哪个资源被锁定，锁定的位置以及如何避免？另一个问题是 - 如何防止这种情况？另一个是：地址0x00007f333e55d000用于什么？

谢谢！

Answer 1

在苦苦挣扎之后，我发现，冻结的线程总是具有相同的名称pool-2-thread-1。我grep项目的所有源代码，以找到任何启动任何预定线程池的地方：Executors#newScheduledThreadPool。经过大量的时间我记录了所有这些地方，线程池中有线程名称。还有一个重启服务器和问题！

我发现了一个线程池，它只用一个线程启动，并使用以下代码：

private void shutdownThreadpool(int tries) {
    try {
        boolean terminated;
        LOGGER.debug("Trying to shutdown thread pool in {} tries", tries);
        pool.shutdown();
        do {
            terminated = pool.awaitTermination(WAIT_ON_SHUTDOWN,TimeUnit.MILLISECONDS);
            if (--tries == 0
                    && !terminated) {
                LOGGER.debug("After 10 attempts couldn't shutdown thread pool, force shutdown");
                pool.shutdownNow();
                terminated = pool.awaitTermination(WAIT_ON_SHUTDOWN, TimeUnit.MILLISECONDS);
                if (!terminated) {
                    LOGGER.debug("Cannot stop thread pool even with force");
                    LOGGER.trace("Some of the workers doesn't react to Interruption event properly");
                    terminated = true;
                }
            } else {
                LOGGER.info("After {} attempts doesn't stop", tries);
            }
        } while (!terminated);
        LOGGER.debug("Successfully stop thread pool");
    } catch (final InterruptedException ie) {
        LOGGER.warn("Thread pool shutdown interrupted");
    }
}

之后问题就解决了。

tomcat：等待条件线程

1 个答案: