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Posted to dev@xmlbeans.apache.org by "Jochen Kemnade (JIRA)" <xm...@xml.apache.org> on 2014/10/17 09:02:34 UTC
[jira] [Commented] (XMLBEANS-502) Usage of XmlBeans triggers
"clearThreadLocalMap" warnings in Tomcat with XSSF
[ https://issues.apache.org/jira/browse/XMLBEANS-502?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14174794#comment-14174794 ]
Jochen Kemnade commented on XMLBEANS-502:
-----------------------------------------
These problem usually occur when you subclass ThreadLocal (usually to implement }}initialValue}}). Those classes reference the webapp's classloader. The ThreadLocal subclass in turn is referenced by each Thread instance (that's how ThreadLocals are implemented, they have a "helper-Map" in each Thread instance, so the leak is actually not a tiny Random instance but the whole webapp's classloader with a bunch of class definitions and statically referenced parts of the webapp.
If you don't subclass ThreadLocal and set the value lazily instead, the problem should be solved.
> Usage of XmlBeans triggers "clearThreadLocalMap" warnings in Tomcat with XSSF
> -----------------------------------------------------------------------------
>
> Key: XMLBEANS-502
> URL: https://issues.apache.org/jira/browse/XMLBEANS-502
> Project: XMLBeans
> Issue Type: Bug
> Affects Versions: Version 2.3
> Environment: Apache Tomcat 6.0.35, Apache POI 3.9-20121203, Java SE 6/7, any operating system
> Reporter: Christopher Brown
> Attachments: leak1.png, leak2.png
>
>
> Hello,
> After creating this issue https://issues.apache.org/bugzilla/show_bug.cgi?id=55149 I was advised to create the issue here. This appears to be similar to https://issues.apache.org/jira/browse/XMLBEANS-103 but as it's marked as FIXED and as I'm using a more recent version (and as it's not completely identical), I'm creating a new issue.
> It would appear that XMLBeans is creating (and not clearing) ThreadLocal variables. This causes Tomcat to complain about classloader leaks (see messages below). Based on information in XMLBEANS-103, I have tried to coax the JVM to clear the ThreadLocal (by performing garbage collection on the JVM), but that doesn't clear the ThreadLocals, even if allowing time to elapse AFTER using POI to process an XSSF document and BEFORE stopping Tomcat.
> To workaround this, we're having to impose long downtime when a restart is required. Perhaps a utility class within XMLBeans could be made available with the POI distribution such as:
> XMLBeansCache.clearThreadLocals()
> ...that I could call from a "finally" block after processing the XSSF document?
> Here's the information from Tomcat's logs:
> SEVERE: The web application [/foobar] created a ThreadLocal with key of type [org.apache.xmlbeans.XmlBeans$1] (value [org.apache.xmlbeans.XmlBeans$1@7d3aace]) and a value of type [java.lang.ref.SoftReference] (value [java.lang.ref.SoftReference@5972be65]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.
> Jun 26, 2013 7:01:56 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap
> SEVERE: The web application [/foobar] created a ThreadLocal with key of type [org.apache.xmlbeans.impl.schema.SchemaTypeLoaderImpl$1] (value [org.apache.xmlbeans.impl.schema.SchemaTypeLoaderImpl$1@7c3206c3]) and a value of type [java.util.ArrayList] (value [[java.lang.ref.SoftReference@385a2be8]]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.
> Jun 26, 2013 7:01:56 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap
> SEVERE: The web application [/foobar] created a ThreadLocal with key of type [org.apache.xmlbeans.impl.store.Locale$1] (value [org.apache.xmlbeans.impl.store.Locale$1@27f8a93f]) and a value of type [java.lang.ref.SoftReference] (value [java.lang.ref.SoftReference@362f7b99]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.
> Jun 26, 2013 7:01:56 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap
> SEVERE: The web application [/foobar] created a ThreadLocal with key of type [org.apache.xmlbeans.impl.store.CharUtil$1] (value [org.apache.xmlbeans.impl.store.CharUtil$1@675b9599]) and a value of type [java.lang.ref.SoftReference] (value [java.lang.ref.SoftReference@2dbaa4d2]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.
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