Java 线程转储：java.lang.Thread.State: WAITING（在对象监视器上）

Question

我们的线程池中有大量线程无限期地等待连接，因为我们的 httpclient 没有任何超时。

线程转储：

"pool-18-thread-400" #471 prio=5 os_prio=0 tid=0x00007fdf37a61000 nid=0x6ed7 in Object.wait() [0x00007fde8df9e000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x00000007263acb18> (a org.apache.commons.httpclient.MultiThreadedHttpConnectionManager$ConnectionPool)
    at org.apache.commons.httpclient.MultiThreadedHttpConnectionManager.doGetConnection(Unknown Source)
    - locked <0x00000007263acb18> (a org.apache.commons.httpclient.MultiThreadedHttpConnectionManager$ConnectionPool)
    at org.apache.commons.httpclient.MultiThreadedHttpConnectionManager.getConnectionWithTimeout(Unknown Source)
    at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(Unknown Source)
    at org.apache.commons.httpclient.HttpClient.executeMethod(Unknown Source)

但我们调用 future.cancel(true) 时将 ma​​yInterruptIfRunning 标志 设置为 true 以在一段时间后终止此​​类长时间运行的线程。这些线程仍在等待连接并且没有被释放。

问题： 为什么这些线程没有被 future.cancel 清理？如果future.cancel 不会释放这些线程，有什么替代步骤可以杀死这种等待徒劳的线程？

添加有关实施的更多信息

我无法分享确切的代码，但提供了一些模拟示例

我们的 ThreadPoolexecutor 有 Unbounded LinkedBlockingQueue，我们未来的任务都是可调用的，我们正在使用 executor.submit(callable) 来执行我们的任务。

public class MockThreadPoolExecutor extends ThreadPoolExecutor {
    public MockThreadPoolExecutor(int numThread) {
        super(numThread,numThread, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>());
        prestartAllCoreThreads();
    }

}

Answer 1

您的线程正在 MultiThreadedHttpConnectionManager.doGetConnection 中的 synchronized (connectionPool) 监视器上等待，该监视器不负责中断。根据getConnectionWithTimeout 的文档，越来越多的maxHostConnections 和maxTotalConnections 可以提供帮助。也可以在http.connection-manager.timeout 中指定超时值，默认为 0，因此线程无限期地等待连接。

/**
 * Gets a connection or waits if one is not available.  A connection is
 * available if one exists that is not being used or if fewer than
 * maxHostConnections have been created in the connectionPool, and fewer
 * than maxTotalConnections have been created in all connectionPools.
 *
 * @param hostConfiguration The host configuration specifying the connection
 *        details.
 * @param timeout the number of milliseconds to wait for a connection, 0 to
 * wait indefinitely
 *
 * @return HttpConnection an available connection
 *
 * @throws HttpException if a connection does not become available in
 * 'timeout' milliseconds
 * 
 * @since 3.0
 */