java - 线程获取已被其他线程获取的 ReentrantLock

Question

我们的应用程序在 WebLogic 12c 中运行，正在从队列系统检索消息，我们从中检索消息的队列被配置为 FIFO。我们使用 Spring 来配置检索功能，容器 (org.springframework.jms.listener.DefaultMessageListenerContainer) 和消息监听器 (org.springframework.jms.core.support.JmsGatewaySupport) 都是单例。此外，该容器默认配置了一个 WorkManager 作为任务执行器。为了保证消息按照预期的顺序(消息发送到队列的顺序)进行处理，我们在监听器中使用了 ReentrantLock，并且我们期望消息被一条一条地检索和处理。监听器代码如下:

public class JmsReceiveAdapterImpl extends JmsGatewaySupport implements SessionAwareMessageListener {
    private final ReentrantLock lock = new ReentrantLock(true);
    [...]
    public void onMessage(Message rcvMessage, Session session) throws JMSException {
        lock.lock();
        logger.warn("Lock has been acquired by thread: " + Thread.currentThread().getId());
        try {
            [...]
        } finally {
            logger.warn("Lock is going to be released by thread: " + Thread.currentThread().getId());
            lock.unlock();
        }
    }
}

即使两条消息以正确的顺序放置在队列中，并且它们按该顺序被消耗(回想一下，队列是 FIFO 队列)，不知何故，这两条消息由应用程序并行处理，如图所示在以下日志 block 中:

    Lock has been acquired by thread: 28
    Backout count: 1
    Message 1 / 1 received from XXX Message ID1 received.
    Lock has been acquired by thread: 54 
    Backout count: 1
    Message 1 / 1 received from XXX Message ID2 received.
    ***** ERROR *****
    Lock is going to be released by thread: 54
    Lock is going to be released by thread: 28

为什么我们会出现这种行为？有什么想法吗？

非常感谢您。

Answer 1

改变

logger.warn("Lock has been acquired by thread: " + Thread.currentThread().getId());

至

logger.warn("Lock has been acquired by thread: " + Thread.currentThread().getId() + " And Object " + System.identityHashCode(this));

您可能会看到 System.identityHashCode 将是两个不同的数字。如果是同一个对象，则identityHashCode 将是相同的。如果它们不同，则意味着它们是不同的对象。

这告诉您有多个 ReentrantLock 实例，并且不支持差异实例上的互斥。