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https://issues.apache.org/jira/browse/DERBY-3745?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12612304#action_12612304
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Brett Kail commented on DERBY-3745:
-----------------------------------

If code is creating a background Thread for its own purposes, then it needs to 
ensure that it does not hold on to an application class loader.  This is true 
for any code intended to run in an application server environment.

If the driver is unloaded, then Derby did seem to properly stop threads in the 
testcase I looked at.  However, in an application server environment, the Derby 
driver cannot be unloaded when a single application is stopped since there can 
be many applications running that all depend on Derby.

> Derby can leak classloaders in an app server environment
> --------------------------------------------------------
>
>                 Key: DERBY-3745
>                 URL: https://issues.apache.org/jira/browse/DERBY-3745
>             Project: Derby
>          Issue Type: Bug
>          Components: Services
>    Affects Versions: 10.3.3.0, 10.4.1.3, 10.5.0.0
>            Reporter: Kathey Marsden
>            Assignee: Kathey Marsden
>         Attachments: derby-3745_10.3_diff.txt, derby-3745_10.3_diff2.txt
>
>
> A user reported potential class loader leaks in Derby
> ...The first one looks like Derby created a long-running
> thread and copying the context class loader.  To fix, the
> context class loader should be saved/set/restored around the
> creation of the new thread so that it copies some benign class
> loader instead (e.g., null or getClass().getClassLoader()):
>  0x42278e58 java/lang/[EMAIL PROTECTED]
>   [truncating at running thread LEAK]
> Object:  0x42278e58 java/lang/[EMAIL PROTECTED]
> Children:
>  0x42278ee0 java/lang/[EMAIL PROTECTED]
>  0x4226e558 java/lang/[EMAIL PROTECTED]
>  0x42278e40
> org/apache/derby/impl/services/monitor/[EMAIL PROTECTED]
>  0x419cfac0
> The second is another long running thread.  The same applies:
>  0x426fe7a0 java/lang/[EMAIL PROTECTED]
>   [truncating at running thread LEAK]
> Object:  0x426fe7a0 java/lang/[EMAIL PROTECTED]
> Parents:
>  0x4226e5a8 [Ljava/lang/Thread;@6f386f38
>  0x426fe548
> org/apache/derby/iapi/services/context/[EMAIL PROTECTED]
> Children:
>  0x426fe838 java/lang/[EMAIL PROTECTED]
>  0x4226e558 java/lang/[EMAIL PROTECTED]
>  0x426fe4f8
> org/apache/derby/impl/services/daemon/[EMAIL PROTECTED]
>  0x419cfac0
> The third is a TimerThread owneed , which is created when a
> Timer is created.  The same applies:
>  0x425ac538 java/util/[EMAIL PROTECTED]
>   [truncating at running thread LEAK]
> Object:  0x425ac538 java/util/[EMAIL PROTECTED]
> Parents:
>  0x41faaf58 [Ljava/lang/Thread;@3c583c58
> Object:  0x425ac510 java/util/[EMAIL PROTECTED]
> Parents:
>  0x425ac500
> org/apache/derby/impl/services/timer/[EMAIL PROTECTED]
> 6e2
> For more info, see thread at:
> http://www.nabble.com/ClassLoader-leaks--td18121374.html

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