[jira] [Reopened] (COCOON-2259) Memory leak in PoolableProxyHandler

["Thorsten Scherler (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/COCOON-2259?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Thorsten Scherler reopened COCOON-2259:
---------------------------------------


We are researching a memoryLeak in a client application and found that this patch is not enough. As reported by  miguel valencia and Mercedes Duarte Madiedo the use of 
this.componentHolder.set(null);
leads to a memory leak.

Our research lead us to 
http://dspace.2283337.n4.nabble.com/ThreadLocals-and-OutOfMemory-td4642935.html
http://www.0xcafefeed.com/2004/06/of-non-static-threadlocals-and-memory/

Since cocoon2.2 is 1.5 compatible using the remove() method is getting rid of the memory leak.
                
> Memory leak in PoolableProxyHandler
> -----------------------------------
>
>                 Key: COCOON-2259
>                 URL: https://issues.apache.org/jira/browse/COCOON-2259
>             Project: Cocoon
>          Issue Type: Bug
>          Components: * Cocoon Core
>    Affects Versions: 2.2, 2.2-dev (Current SVN)
>            Reporter: Alexander Daniel
>            Assignee: Thorsten Scherler
>             Fix For: 2.2-dev (Current SVN)
>
>         Attachments: patchForIssue2259.txt
>
>
> I reproduced the problem with following pipeline and by adding log output to PoolableProxyHandler [1]
> <map:pipeline id="cocoonTest" type="noncaching">
> 	<map:match pattern="cocoonProtocol">
> 		<map:generate src="cocoon://sub"/>
> 		<map:serialize type="xhtml"/>
> 	</map:match>
> 	<map:match pattern="sub">
> 		<map:generate src="welcome/welcome.xml"/>
> 		<map:transform src="welcome/welcome.xslt"/>
> 		<map:serialize type="xhtml"/>
> 	</map:match>
> </map:pipeline>
> Changing the line 
>      this.attributeName = PoolableProxyHandler.class.getName() + '/' + this.handler.hashCode();
> to
>      this.attributeName = PoolableProxyHandler.class.getName() + '/' + this.hashCode();
> fixes the memory leak.
> Why? The PoolableFactoryBean [2] handler is a singleton for every pipeline component, i.e. one instance for noncaching pipeline, one instance for xalan transformer, ... Therefore the attributeName is the same for every component of the same type but Spring requires an unique value for the destruction callback handler.
> In the example sitemap above two noncaching pipeline instances are needed for processing the request. Both call registerDestructionCallback with the same attributeName. Because the attributeName is the same the callback is only called once and the other component remains in ThreadLocal.
> [1] http://svn.apache.org/repos/asf/cocoon/trunk/core/cocoon-sitemap/cocoon-sitemap-impl/src/main/java/org/apache/cocoon/core/container/spring/avalon/PoolableProxyHandler.java
> [2] http://svn.apache.org/repos/asf/cocoon/trunk/core/cocoon-sitemap/cocoon-sitemap-impl/src/main/java/org/apache/cocoon/core/container/spring/avalon/PoolableFactoryBean.java

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