Question

我正在使用Amazon Web Services AWS Java SDK编写Web应用程序。 Apache commons HttpClient版本3在幕后使用。我有commons-httpclient-3.0.1.jar。

我的catalina.out中有以下警告

SEVERE: The web application [/MyAppName] appears to have started a thread named
[MultiThreadedHttpConnectionManager cleanup] but has failed to stop it. This is 
very likely to create a memory leak.

所以我用contextDestroyed（）方法编写了一个ServletContextListener，调用：

MultiThreadedHttpConnectionManager.shutdownAll();

然而，警告仍然显示，尽管已经调用了方法。我还应该做些什么来确保清理？

编辑：我想绝对确定contextDestroyed（）确实被调用（建议使用nos），所以我在方法的第一个语句上放置了一个断点，停止了服务器和断点被击中我一步一步地执行了该方法，以确保不会引发异常，并且方法的每一行都没有问题地执行。这是我的源代码：

@Override
public void contextDestroyed(ServletContextEvent servletContextEvent) {
    System.out.println("contextDestroyed() start");
    MyMemCache.shutDown();
    MultiThreadedHttpConnectionManager.shutdownAll();
    ClassLoader contextClassLoader=Thread.currentThread().getContextClassLoader();
    LogFactory.release(contextClassLoader);
    java.beans.Introspector.flushCaches();
    System.out.println("contextDestroyed() end");
}

热插拔时：

INFO: Reloading Context with name [/MyAppName] has started
contextDestroyed() start
contextDestroyed() end
05 24, 11 3:11:00 PM org.apache.catalina.loader.WebappClassLoader 
    clearReferencesThreads
SEVERE: The web application [/MyAppName] appears to have started a thread 
    named [MultiThreadedHttpConnectionManager cleanup] but has failed to 
    stop it. This is very likely to create a memory leak.

Answer 1

这是AWS SDK中的一个错误，它会打开两个HttpClients并仅关闭其中一个。我的问题略有不同，因为我想在不重新启动webapp的情况下启动和停止各个地区和帐户的客户端。

我已经解决了这个问题（我已向他们报告，但他们似乎并不倾向于修复）：

public class MyAmazonEC2Client extends AmazonEC2AsyncClient {
    private boolean shutdownCalled = false;


    public MyAmazonEC2Client(final AWSCredentials awsCredentials) {
        super(awsCredentials);
    }


    public MyAmazonEC2Client(final AWSCredentials awsCredentials, final ClientConfiguration clientConfiguration) {
        this(awsCredentials, clientConfiguration, Executors.newCachedThreadPool());
    }


    public MyAmazonEC2Client(
                                 final AWSCredentials awsCredentials,
                                 final ClientConfiguration clientConfiguration,
                                 final ExecutorService executor) {
        super(awsCredentials, clientConfiguration, executor);
    }


    /**
     * Shuts down this client object, releasing any resources that might be held open.<br />
     */
    @Override
    public synchronized void shutdown() {
        try {
            shutdownCalled = true;

            // Call the proper shutdown method. This is in the base type and only shuts down one of the HttpClients created (the one that's never used)
            super.shutdown(); // close the HttpClient in AmazonWebServiceClient
        }
        finally {
            // Fix a bug in Amazon's implementation where they've duplicated the HttpClients
            try {
                super.client.shutdown(); // close the HttpClient in AmazonEC2Client
            }
            catch (Throwable t) {
                // ignore failures
            }
        }
    }
}

Answer 2

更新到AWS Java SDK 1.2.1版解决了这个问题。自我于2011年5月26日发布以来，我在发布问题时尚未提供此版本。

AWS SDK 1.2。*使用2009年发布的HttpClient 4，但AWS Java SDK仍在1.1。*版本中使用版本3。自从我的问题解决后，我不会进一步详细分析他们的代码更改。

Answer 3

我在axis2 web服务中也遇到了类似的错误，发现它是轴bug，在axis2 1.6版本中已修复。

虽然这个问题已经回答了AWS，但我已经为那些正在寻找类似的axis2错误的人提供了答案。

启动了名为MultiThreadedHttpConnectionManager清理的线程，但未能将其停止

3 个答案: