java - Tomcat8内存泄漏

Question

当我尝试在 Java 8 上停止 tomcat8 时，出现一些内存泄漏错误:

org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] appears to have started a thread named [Abandoned connection cleanup thread] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.lang.Object.wait(Native Method)
 java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:142)
 com.mysql.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:40)
23-Jan-2015 08:18:10.202 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] appears to have started a thread named [pool-5-thread-1] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread


23-Jan-2015 08:18:10.205 SEVERE [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.checkThreadLocalMapForLeaks The web application [ROOT] created a ThreadLocal with key of type [com.util.ThreadLocalProperties$1] (value [com.util.ThreadLocalProperties$1@2fafda6e]) and a value of type [java.util.Properties] (value [{}]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.

ThreadLocalProperties 类是:

public class ThreadLocalProperties extends Properties {

    private static final long serialVersionUID = -4260632266508618756L;
    private final ThreadLocal<Properties> localProperties = new ThreadLocal<Properties>() {
        @Override
        protected Properties initialValue() {
            return new Properties();
        }
    };

    public ThreadLocalProperties(Properties properties) {
        super(properties);
    }

    @Override
    public String getProperty(String key) {
        String localValue = localProperties.get().getProperty(key);
        return localValue == null ? super.getProperty(key) : localValue;
    }

    @Override
    public Object setProperty(String key, String value) {
        return localProperties.get().setProperty(key, value);
    }

    public ThreadLocal<Properties> getThreadLocal() {
        return localProperties;
    }
}

然后我像这样开始和停止它:

@WebListener()
public class GeneralListener implements ServletContextListener {

    ThreadLocalProperties threadLocalProperties = new ThreadLocalProperties(System.getProperties());

    @Override
    public void contextDestroyed(ServletContextEvent arg0) {
        threadLocalProperties.getThreadLocal().remove();
    }

    @Override
    public void contextInitialized(ServletContextEvent arg0) {
        System.setProperties(threadLocalProperties);
    }
}

为什么我会得到所有这些内存泄漏错误？同样，当我运行关机时，它并没有关闭它，我必须手动终止该进程。

怎么了？

Answer 1

没有什么可担心的。这是当它检测到应用程序已启动它自己的 Thread 或创建了 ThreadLocal 时，tomcat 输出的标准消息。如果您在关闭时终止线程并在不再需要 threadlocals 时删除它们，则不会有问题。

Why would I get all this memory leaks errors? as well, when I run shutdown, it doesn't shut it down, I have to manually kill the process.

我见过这种行为，当应用程序启动 ScheduledExecutor 时(但任何其他 Thread/TheadPool 都会发生这种情况)并且没有在 contextDestroyed 上关闭它。因此，请检查您是否在应用程序/服务器停止时关闭线程。

现在谈谈你的具体问题为什么服务器没有停止:JDBC 驱动程序在 JVM 中注册为单例，并与所有 Web 应用程序共享。更多信息 here.解决问题的最佳方法是将 MySQL 驱动程序移动到 Tomcat 的 /lib 文件夹中。如果你做不到，你可以试试this但它更像是一种 hack，而不是真正的解决方案。