Permgen内存泄漏，具有热重新部署和Oracle数据库

Question

我有一个在生产环境中运行的基于SpringRoo的应用程序，在一些热重新部署后导致严重的permgen内存泄漏。

为了“找到并修复”泄漏并在分析过程中减少变量，我使用roo创建了一个简单，简化的应用程序，并获得了相同的行为。 该项目（使用Spring Roo（1.2.3.RELEASE）创建）仅使用名为“name”的字符串字段持久保存名为“Person”的实体。

我使用Oracle 11.2.0.2作为数据库在Tomcat 7.0.39上部署战争。 每次重新部署后，我都会在catalina.out

中收到此消息

INFO: Undeploying context [/ojdbc-0.1.0.BUILD-SNAPSHOT]
mag 06, 2013 10:50:43 AM org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
SEVERE: The web application [/ojdbc-0.1.0.BUILD-SNAPSHOT] registered the JDBC driver       [oracle.jdbc.OracleDriver] but failed to unregister it when the web application was stopped.    To prevent a memory leak, the JDBC Driver has been forcibly unregistered.

经过两次热重新曝光后，我收到 permgen错误：

mag 06, 2013 10:51:08 AM org.apache.catalina.startup.HostConfig deployWAR
INFO: Deploying web application archive /Applications/apache-tomcat-7.0.39/webapps/ojdbc-    0.1.0.BUILD-SNAPSHOT.war
Exception in thread "ContainerBackgroundProcessor[StandardEngine[Catalina]]"
Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "ContainerBackgroundProcessor[StandardEngine[Catalina]]"
Exception in thread "RMI TCP Connection(idle)" mag 06, 2013 10:51:17 AM ServerCommunicatorAdmin reqIncoming
WARNING: The server has decided to close this client connection.
java.lang.OutOfMemoryError: PermGen space
Exception in thread "RMI TCP Connection(idle)" java.lang.OutOfMemoryError: PermGen space

我尝试使用VisualVm / EclipseMemory Analyzer进行分析，这是我到目前为止所做的。

事实是我没有观察到另一个数据库（例如PostgreSQL或Hypersonic）的这种行为。是否有与Oracle相关的问题导致泄漏？

Here是一个包含roo脚本生成器的zip存档，它是.hprof转储文件。

Answer 1

尝试将Oracle JDBC驱动程序移动到Tomcat的lib目录中，而不是在应用程序的lib文件夹中。看起来OracleDiagnosabilityMBean正在处理Catalina。

编辑：由于您无法控制Tomcat，请尝试将Oracle类加载到哪里（除了替换Oracle init的AppContext）：

http://cdivilly.wordpress.com/2012/04/23/permgen-memory-leak/

//somewhere in application startup, e.g. the ServletContextListener
try {
 final ClassLoader active = Thread.currentThread().getContextClassLoader();
 try {
  //Find the root classloader
  ClassLoader root = active;
  while (root.getParent() != null) {
   root = root.getParent();
  }
  //Temporarily make the root class loader the active class loader
  Thread.currentThread().setContextClassLoader(root);
  //Force the AppContext singleton to be created and initialized
  sun.awt.AppContext.getAppContext();
 } finally {
 //restore the class loader
 Thread.currentThread().setContextClassLoader(active);   
}
} catch ( Throwable t) {
   //Carry on if we get an error
   LOG.warning("Failed to address PermGen leak");
}

Answer 2

有一个内部Oracle错误报告

Oracle Support Bug 18707079 (JDBC THIN DRIVER LEAKS THREADS AND REFERENCES ON WEBAPP SHUTDOWN): https://support.oracle.com/epmos/faces/BugDisplay?id=18707079

描述了您的问题：

When the webapp is shutdown, customer experience the following problems:
1) The OracleDiagnosabilityMBean is not de-registered
2) OracleTimeoutPollingThread does not stop
3) The following thread does not stop: 
oracle.jdbc.driver.BlockSource.ThreadedCachingBlockSource.BlockReleaser

设置为Fixed in Product Version 12.2。希望它很快就会发布！

Answer 3

试试这个：

在web xml中注册ServletContextListener

<listener>
    <listener-class>my.package.MyShutdownServletContextListener</listener-class>
</listener>

源：

public class MyShutdownServletContextListener implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent event) {
    final ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();
    try {
        Thread.currentThread().setContextClassLoader(ClassLoader.getSystemClassLoader());
        java.sql.DriverManager.getDrivers();
        Class.forName("oracle.jdbc.driver.OracleTimeoutThreadPerVM");
    } catch (ClassNotFoundException e) {
        /* noop */
    } finally {
        Thread.currentThread().setContextClassLoader(contextClassLoader);
    }
}
@Override
public void contextDestroyed(ServletContextEvent event) {}
}