7:18 a.m.
ud1 [https://community.jboss.org/people/ud1] created the discussion
"Jboss AOP classloading bug"
To view the discussion, visit: https://community.jboss.org/message/715200#715200
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I'm using JBoss 6.0.0 with AOP for logging user actions and function call durations.
Functions of interest are marked by our custom @Trace annotation and there is an our
tracing aspect, that do all the work. But sometimes, probably after jboss restart, some
random functionality of the project becomes unavailable, e.g. some dropdown lists
didn't working or some buttons pressing do nothing. After second rebooting everething
work fine. I can't reproduce this on my machine, but customers regulary (once or twice
a month) reporting about the problem. Here is the typical log with org.jboss.classpool
logging on:
http://pastebin.com/f4TEduCB http://pastebin.com/f4TEduCB
When all is functioning properly the log look's like:
http://pastebin.com/zZKPk643 http://pastebin.com/zZKPk643
I have made some investigation and degugging, so probably I have found the cause of the
problem.
At first, if you look at ClassPoolToDomainAdapter with a lot of byte array class paths in
it, you could see the difference, at normal working this list
contains
BaseClassLoader@xxxxxx{vfs:///D:/retailHub/loan/server/default/deploy/myProject.ear}
ClassPath at the end, but then the problem is it doesn't.
After deepest code investigation I figured out, that this could happen then something call
close() on а ClassPool, and this probably happens inside unregisterClassLoader()
function.
During joint point constraction Aspect Manager calls several times unregisterClassLoader()
function:
ClassPoolRepository
public void unregisterClassLoader(ClassLoader classLoader)
{
registryHandler.unregisterClassLoader(classLoader); // <-- calls
JBossClRegistryHandler.unregisterClassLoader()
if (callbacks != null && callbacks.size() > 0)
{
for (ClassPoolRepositoryCallback callback : callbacks)
{
callback.classLoaderUnregistered(classLoader);
}
}
}
which in turn calls JBossClRegistryHandler.registerClassLoader() functions with possible
result of a closing the class pool.
JBossClRegistryHandler
public ClassPool registerClassLoader(ClassLoader classLoader)
{
ScopedClassPool classPool = (ScopedClassPool)
successor.registerClassLoader(classLoader);
if (classPool == null) // <-- true
{
// TODO check this works; was delegate before
successor.unregisterClassLoader(classLoader); // <-- calls
classLoader.close()
}
else
{
Module module = getModuleForClassLoader(classLoader);
this.registeredModules.put(module, classPool);
}
return classPool;
}
I can't understand what is the purpose of the DefaultClassLoaderRegistryHandler, but
it can return null from registerClassLoader() function,
probaly then several jointpoints are generated concurrently from different threads:
ClassPoolRepository$DefaultClassLoaderRegistryHandler
public ClassPool registerClassLoader(ClassLoader classLoader)
{
if (classLoader == null)
{
classLoader = SecurityActions.getContextClassLoader();
}
if (currentClassLoaders.putIfAbsent(classLoader, Boolean.TRUE) != null)
{
return null; // <-- Returns null
}
ScopedClassPool classPool = (ScopedClassPool)
ClassPoolRepository.super.registerClassLoader(classLoader);
currentClassLoaders.remove(classLoader);
return classPool;
}
ScopedClassPoolRepositoryImpl:
public void unregisterClassLoader(ClassLoader cl) {
synchronized (registeredCLs) {
ScopedClassPool pool = registeredCLs.remove(cl);
if (pool != null)
pool.close(); // <-- close
}
}
ScopedClassPool:
public void close() {
this.removeClassPath(classPath); // <-- remove
BaseClassLoader@xxxxxx{vfs:///D:/retailHub/loan/server/default/deploy/myProject.ear}
classpath
classPath.close();
classes.clear();
softcache.clear();
}
During joint point creation the myProject.war class loader is used, it redirects calls to
JBossClClassPoolDomain, and in turn to SuperClassesFirstWeavingStrategy, and finally
the reference to the old ClassPool (with a lot of byte array class paths) is used. Is has
no myProject.ear ClassLoader any more, so NotFoundException is fired.
I don't know how to fix this, I will appreciate your help.
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