Guice 3.0 + Tomcat 7.0 = ClassLoader内存泄漏 [英] Guice 3.0 + Tomcat 7.0 = ClassLoader memory leak

问题描述

我知道这个问题已经存在至少3年了（ Issue 92 ），但我仍然不满意当前的状态。我也知道如果重新部署后重新启动，这不会影响Tomcat（如 Guice +中所述） Tomcat潜在的内存泄漏）。

我的问题是我在重新部署后遇到 OutOfMemoryError：PermGen 错误。请注意，我没有明确使用google-collections，我只使用Guice 3.0（通过maven）。在分析堆转储之后，我仍然看到线程 com.google.inject.internal.Finalizer 仍处于活动状态，保留对Tomcat的WebappClassLoader的引用，从而阻碍了垃圾回收。 / p>

如果我实际上需要重新部署而不重新启动并使用Guice会怎样？我有什么选择？

解决方案

好吧，没有人帮助我，所以这就是我所学到的：

Finalizer线程由FinalizableReferenceQueue（FRQ）启动。 MapMaker中有一个对FRQ的硬（静态）引用。 WebAppClassLoader没有被垃圾收集，因为由于硬参考，MapMaper仍然存在。

以下代码解决我的问题：

  final Class<？> queueHolderClass = 
 Class.forName（com.google.inject.internal.util。$ MapMaker $ QueueHolder）; 
 final字段queueField = queueHolderClass.getDeclaredField（queue）; 
 //使MapMaker.QueueHolder.queue可访问
 queueField.setAccessible（true）; 
 //从MapMaker.QueueHolder.queue中移除最终修饰符
 final Field modifiersField = Field.class.getDeclaredField（modifiers）; 
 modifiersField.setAccessible（true）; 
 modifiersField.setInt（queueField，queueField.getModifiers（）& ~Modifier.FINAL）; 
 //将其设置为null 
 queueField.set（null，null）; 
  

以下是违规代码（ com.google .inject.internal.util.MapMaker ）：

  / **包装类确保队列不存在直到它被使用才被创造。 * / 
私有静态类QueueHolder {
静态final finalizableReferenceQueue queue = new FinalizableReferenceQueue（）; 
} 
  

执行此操作后，Finalizer线程会正常死亡。

I know that this problem has been around for at least 3 yeears (Issue 92), but I'm still not satisfied with the current state of it. I am also aware that this does not affect Tomcat if you do restart after redeploying (as suggested in Guice + Tomcat potential memory leak).

My problem is that I am experiencing OutOfMemoryError: PermGen errors after some redeployments. Notice that I am not using google-collections explicitly, I am only using Guice 3.0 (via maven). After analyzing heap dumps, I still see that the thread com.google.inject.internal.Finalizer is still active, keeps a reference to Tomcat's WebappClassLoader, thus hindering garbage collection.

What if I actually require redeployments without restarting and am using Guice? What are my options?

解决方案

Well, no one was there to help me, so here's what I learned:

The Finalizer thread is started by the FinalizableReferenceQueue (FRQ). There is a hard (static) reference to the FRQ in MapMaker. The WebAppClassLoader was not garbage collected because MapMaper was still around due to the hard reference.

The following code solved my problem:

final Class<?> queueHolderClass = 
    Class.forName("com.google.inject.internal.util.$MapMaker$QueueHolder");
final Field queueField = queueHolderClass.getDeclaredField("queue");
// make MapMaker.QueueHolder.queue accessible
queueField.setAccessible(true);
// remove the final modifier from MapMaker.QueueHolder.queue
final Field modifiersField = Field.class.getDeclaredField("modifiers");
modifiersField.setAccessible(true);
modifiersField.setInt(queueField, queueField.getModifiers() & ~Modifier.FINAL);
// set it to null
queueField.set(null, null);

Here's the offending code (com.google.inject.internal.util.MapMaker):

/** Wrapper class ensures that queue isn't created until it's used. */
private static class QueueHolder {
  static final FinalizableReferenceQueue queue = new FinalizableReferenceQueue();
}

After doing this, the Finalizer thread gracefully dies.

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