[jboss-jira] [JBoss JIRA] Closed: (JBCOMMON-50) TimedCachePolicy leaks classloader to timer thread
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https://jira.jboss.org/jira/browse/JBCOMMON-50?page=com.atlassian.jira.pl...
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Brian Stansberry closed JBCOMMON-50.
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Resolution: Done
Done.
By default, the class now sets the current threads context classloader to the system
classloader before creating the Timer. This is fine for the internal usage of this class,
where the timer tasks just call System.currentTimeMillis() (in TimedCachePolicy.run()).
But, since common-core is a utility library and people may have subclassed
TimedCachePolicy to do more in run(),[1] I added the ability to control what classloader
is used. This can be done by setting the system property
"jboss.common.timedcachepolicy.timer.classloader". Possible values are:
"system" -- use the system classloader (the default)
"current" -- use TimedCachePolicy.class.getClassLoader()
"context" -- use TCCL
If any SecurityException is thrown reading the system property or changing the TCCL, the
old method is left in place.
[1] I looked in the AS codebase, including integrated libs, and saw no subclassing.
TimedCachePolicy leaks classloader to timer thread
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Key: JBCOMMON-50
URL: https://jira.jboss.org/jira/browse/JBCOMMON-50
Project: JBoss Common
Issue Type: Bug
Security Level: Public(Everyone can see)
Components: common-core (2.x)
Affects Versions: 2.2.4.GA, 2.2.5.beta1
Reporter: Brian Stansberry
Assignee: Brian Stansberry
Fix For: 2.2.12.GA
Attachments: JBCOMMON-50.patch
TimedCachePolicy has a static reference to a Timer, restartTimer. A timer creates a new
thread when it is initialized; the thread inherits its TCCL from the TCCL of the thread
that initializes it. Effect is that TCCL leaks to the restartTimer's thread.
Not sure the best solution here, since common-core is a general use library. In general I
think the right solution is to set the TCCL to a "safe" classloader before
creating the Timer, and restore the TCCL afterwards. But what is a "safe"
classloader? If you use TimedCachePolicy.class.getClassLoader(), then that classloader is
leaked. That's fine in JBoss AS, but may be bad in other use cases. Perhaps null or
system classloader is the right choice; I don't know enough about how this class is
used to have a good idea if the TimerTasks being used (seems to only be RestartTimer) need
to load classes.
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