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https://issues.apache.org/jira/browse/KARAF-4687?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15452658#comment-15452658
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Grzegorz Grzybek commented on KARAF-4687:
-----------------------------------------
All leaks are related to {{java.lang.Exception#classContext}} field added for
pax-logging in {{karaf/exception/src/main/java/java/lang/Exception.java}}.
The problem is related to one of the worst patterns that are very very bad in
OSGi - static instances of Throwables.
Even without the improvement for pax-logging (additional classContext field)
there's natively visible field called {{backtrace}} - see more details here:
https://github.com/eclipse/jetty.project/issues/868.
First leak can be solved by changing Class array into WeakReference<Class> array
Second leak can be fixed by using special JDK7 Throwable constructor that
allows to configure whether stacktrace/backtrace should be set/initialized at
all - this is great improvement for those who like static instances of
Throwables. But *they should be avoided at all cost* in OSGi (and generally).
If only we could change xerces code to use this new constructor for
org.apache.xerces.impl.XMLEntityScanner.END_OF_DOCUMENT_ENTITY static
Throwable... If we could, we won't have to change Class array into
WeakReference<Class> array...
> ClassLoader leak with java.lang.Exception and karaf.exception library
> ---------------------------------------------------------------------
>
> Key: KARAF-4687
> URL: https://issues.apache.org/jira/browse/KARAF-4687
> Project: Karaf
> Issue Type: Bug
> Affects Versions: 2.4.4, 4.0.6, 3.0.8
> Reporter: Grzegorz Grzybek
>
> Here's much worse leak I found in JVisualVM:
> {noformat}
> this - value: org.apache.felix.framework.BundleWiringImpl #1
> <- m_wiring - class:
> org.apache.felix.framework.BundleWiringImpl$BundleClassLoaderJava5, value:
> org.apache.felix.framework.BundleWiringImpl #1
> <- <classLoader> - class: org.ops4j.pax.logging.slf4j.Slf4jLogger,
> value: org.apache.felix.framework.BundleWiringImpl$BundleClassLoaderJava5 #1
> <- <class> - class: org.ops4j.pax.logging.slf4j.Slf4jLogger, value:
> org.ops4j.pax.logging.slf4j.Slf4jLogger class Slf4jLogger
> <- LOGGER - class:
> org.apache.karaf.features.internal.FeaturesServiceImpl, value:
> org.ops4j.pax.logging.slf4j.Slf4jLogger #3
> <- [19] - class: java.lang.Class[], value:
> org.apache.karaf.features.internal.FeaturesServiceImpl class
> FeaturesServiceImpl
> <- classContext - class: org.apache.xerces.impl.XMLEntityScanner$1,
> value: java.lang.Class[] #23
> <- END_OF_DOCUMENT_ENTITY (sticky class) - class:
> org.apache.xerces.impl.XMLEntityScanner, value:
> org.apache.xerces.impl.XMLEntityScanner$1 #1
> {noformat}
> and
> {noformat}
> this - value: org.apache.felix.framework.BundleWiringImpl #18
> <- m_wiring - class:
> org.apache.felix.framework.BundleWiringImpl$BundleClassLoaderJava5, value:
> org.apache.felix.framework.BundleWiringImpl #18
> <- <classLoader> - class: io.fabric8.api.scr.ValidatingReference,
> value: org.apache.felix.framework.BundleWiringImpl$BundleClassLoaderJava5 #16
> <- <class> - class: io.fabric8.api.scr.ValidatingReference, value:
> io.fabric8.api.scr.ValidatingReference class ValidatingReference
> <- curator - class:
> io.fabric8.zookeeper.curator.CuratorFrameworkLocator, value:
> io.fabric8.api.scr.ValidatingReference #1
> <- [140] - class: java.lang.Object[], value:
> io.fabric8.zookeeper.curator.CuratorFrameworkLocator class
> CuratorFrameworkLocator
> <- elementData - class: java.util.Vector, value: java.lang.Object[]
> #3790
> <- classes - class:
> org.apache.felix.framework.BundleWiringImpl$BundleClassLoaderJava5, value:
> java.util.Vector #120
> <- <classLoader> - class:
> io.fabric8.zookeeper.curator.ManagedCuratorFramework$State, value:
> org.apache.felix.framework.BundleWiringImpl$BundleClassLoaderJava5 #15
> <- [93] - class: java.lang.Class[], value:
> io.fabric8.zookeeper.curator.ManagedCuratorFramework$State class
> ManagedCuratorFramework$State
> <- classContext - class:
> org.eclipse.jgit.errors.StopWalkException, value: java.lang.Class[] #946
> <- INSTANCE - class:
> org.eclipse.jgit.errors.StopWalkException, value:
> org.eclipse.jgit.errors.StopWalkException #1
> <- [332] - class: java.lang.Object[], value:
> org.eclipse.jgit.errors.StopWalkException class StopWalkException
> <- elementData - class: java.util.Vector, value:
> java.lang.Object[] #3772
> <- classes - class:
> org.apache.felix.framework.BundleWiringImpl$BundleClassLoaderJava5, value:
> java.util.Vector #119
> <- <classLoader> - class: org.eclipse.jgit.nls.NLS, value:
> org.apache.felix.framework.BundleWiringImpl$BundleClassLoaderJava5 #14
> <- <class> - class: org.eclipse.jgit.nls.NLS, value:
> org.eclipse.jgit.nls.NLS class NLS
> <- value - class:
> java.lang.ThreadLocal$ThreadLocalMap$Entry, value: org.eclipse.jgit.nls.NLS #1
> <- [11] - class:
> java.lang.ThreadLocal$ThreadLocalMap$Entry[], value:
> java.lang.ThreadLocal$ThreadLocalMap$Entry #144
> <- table - class:
> java.lang.ThreadLocal$ThreadLocalMap, value:
> java.lang.ThreadLocal$ThreadLocalMap$Entry[] #1
> <- inheritableThreadLocals (thread object) - class:
> java.lang.Thread, value: java.lang.ThreadLocal$ThreadLocalMap #2
> {noformat}
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