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From Ruslan Gainutdinov <rusla...@gmail.com>
Subject In cluster, when using DeltaManager memory leak can occur
Date Thu, 09 Sep 2010 11:00:25 GMT
Tested on apache-tomcat-6.0.29 running under jdk 1.6.0_18.

When DeltaManager is instantiated and assigned in StandardContext.start(),
is it done AFTER StandardContext.bindThreads().

DeltaManager, in turn, during initalization, asks for sessions in other nodes,
and this may result in creating threads ThreadPoolExecutor in tribes.

These threads created with contextClassLoader set to current
webapplication WebAppClassLoader.

This results in memory leak and error message during redeployment in tomcat log:

09/09/2010 14:46:19 S - - WebappClassLoader.clearReferencesThreads:
The web application [/creditdev] appears to have started a thread
named [pool-1-thread-1] but has failed to stop it. This is very likely
to create a memory leak.

Stacktrace:
	at java.util.concurrent.ThreadPoolExecutor.addThread(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor.addIfUnderCorePoolSize(Unknown
Source)
	at java.util.concurrent.ThreadPoolExecutor.execute(Unknown Source)
	at org.apache.catalina.tribes.group.interceptors.MessageDispatch15Interceptor.addToQueue(MessageDispatch15Interceptor.java:67)
	at org.apache.catalina.tribes.group.interceptors.MessageDispatchInterceptor.sendMessage(MessageDispatchInterceptor.java:68)
	at org.apache.catalina.tribes.group.ChannelInterceptorBase.sendMessage(ChannelInterceptorBase.java:75)
	at org.apache.catalina.tribes.group.interceptors.TcpFailureDetector.sendMessage(TcpFailureDetector.java:87)
	at org.apache.catalina.tribes.group.ChannelInterceptorBase.sendMessage(ChannelInterceptorBase.java:75)
	at org.apache.catalina.tribes.group.GroupChannel.send(GroupChannel.java:216)
	at org.apache.catalina.tribes.group.GroupChannel.send(GroupChannel.java:175)
	at org.apache.catalina.ha.tcp.SimpleTcpCluster.send(SimpleTcpCluster.java:813)
	at org.apache.catalina.ha.session.DeltaManager.getAllClusterSessions(DeltaManager.java:959)
	at org.apache.catalina.ha.session.DeltaManager.start(DeltaManager.java:930)
	at org.apache.catalina.core.ContainerBase.setManager(ContainerBase.java:438)
	at org.apache.catalina.core.StandardContext.start(StandardContext.java:4559)
	at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
	at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
	at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:546)
	at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:637)
	at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:563)
	at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:498)
	at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1277)
	at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:321)
	at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
	at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
	at org.apache.catalina.core.StandardHost.start(StandardHost.java:785)
	at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
	at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:445)
	at org.apache.catalina.core.StandardService.start(StandardService.java:519)
	at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
	at org.apache.catalina.startup.Catalina.start(Catalina.java:581)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
	at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.tanukisoftware.wrapper.WrapperStartStopApp.run(WrapperStartStopApp.java:243)
	at java.lang.Thread.run(Unknown Source)

Proposed solution - implement java.util.concurrent.ThreadFactory in
MessageDispatch15Interceptor
and pass instance on ThreadPoolExecutor executor creation.

This instance must call setContextClassLoader(null) in newThread()
overriden method.

With kindest personal regards,
Ruslan Gainutdinov
<ruslanfg@gmail.com>

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