[ openjms-Bugs-1107742 ] Clock Daemon Thread never exits in Applet

Bugs item #1107742, was opened at 2005-01-23 23:32
Message generated for change (Settings changed) made by tanderson
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Category: client
Group: v0.7.6.1
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Tim Anderson (tanderson)
>Assigned to: Tim Anderson (tanderson)
Summary: Clock Daemon Thread never exits in Applet

Initial Comment:
[Originally from 
http://article.gmane.org/gmane.comp.java.openjms.use
r/2231 ]

In an applet environment, the Clock daemon thread 
raises the following stack traces when the applet is 
exited:

SEVERE: Internal error in clock daemon
java.lang.InterruptedException: sleep interrupted
    at java.lang.Thread.sleep(Native Method)
    at org.exolab.jms.util.Clock.run(Clock.java:210)

followed closely by:

SEVERE: Internal error in clock daemon
java.lang.ThreadDeath
    at java.lang.Thread.stop(Thread.java:630)
    at java.lang.ThreadGroup.stopOrSuspend
(ThreadGroup.java:633)
    at java.lang.ThreadGroup.stop
(ThreadGroup.java:547)
    at sun.awt.AppContext.dispose(AppContext.java:411)
    at sun.applet.AppletClassLoader.release
(AppletClassLoader.java:668)
    at sun.plugin.security.PluginClassLoader.release
(PluginClassLoader.java:407)
    at sun.applet.AppletPanel.release
(AppletPanel.java:168)
    at sun.applet.AppletPanel.sendEvent
(AppletPanel.java:265)
    at sun.plugin.AppletViewer.onPrivateClose
(AppletViewer.java:834)
    at sun.plugin.AppletViewer$1.run
(AppletViewer.java:796)
    at java.lang.Thread.run(Thread.java:534)


To make matters worse, once this error is raised 
dumping the running threads shows this (after 
numerous runs):
Dump thread list ...
Group main,ac=20,agc=10,pri=10
    main,5,alive
    AWT-Motif,6,alive,dameon
    AWT-Shutdown,5,alive
    Thread-1,5,alive
    Thread-2,5,alive
    AWT-EventQueue-0,6,alive
Group Plugin Thread Group,ac=4,agc=0,pri=10
    Main Console Writer,6,alive
    AWT-EventQueue-1,6,alive
    Java2D Disposer,10,alive,dameon
    TimerQueue,5,alive,dameon
Group http://myserver/myappletpage/-
threadGroup,ac=1,agc=0,pri=4
    Clock Daemon,4,alive,dameon
Group http://myserver/myappletpage/-
threadGroup,ac=1,agc=0,pri=4
    Clock Daemon,4,alive,dameon
Group http://myserver/myappletpage/-
threadGroup,ac=1,agc=0,pri=4
    Clock Daemon,4,alive,dameon
 ...

Which also causes the memory to never be released.  
Obviously some object is being referenced by this 
running thread which causes JMS to never release 
memory - as evidenced by this:

Garbage collect ... completed.
Memory: 47,368K  Free: 21,342K  (45%) ... completed.

Looking at the code for "org.exolab.jms.util.Clock" - the 
run() method has no safe exit condition, running in 
a "while(true)" block...........   I assume that this causes 
the ThreadDeath exception - which in turn could cause 
the Applet code to stop destroying the thread group - 
thus keeping objects references which should be gone.  
A simple thread exit condition here may fix this.

Ken M.



----------------------------------------------------------------------

Comment By: Tim Anderson (tanderson)
Date: 2005-03-26 00:24

Message:
Logged In: YES 
user_id=557161

Fixed in CVS. Fix will be available in the 0.7.7 release.

----------------------------------------------------------------------

Comment By: Tim Anderson (tanderson)
Date: 2005-01-23 23:33

Message:
Logged In: YES 
user_id=557161

Changing the Clock code so that run() looks something like:
 
        while (true) {
            try {
                for (int i = 0; i < _synchEvery; ++i) {
                    sleep(_unsynchTicks);
                    synchronized (Clock.class) {
                        _clock += _unsynchTicks + _adjust;
                    }
                }
                synchronize();
            } catch (ThreadDeath exception) {
                _log.debug("clock daemon terminating", 
exception);
                throw exception;
            } catch (Throwable exception) {
                _log.error("Internal error in clock daemon", 
exception);
            }
        }
 
should correct the problem.

----------------------------------------------------------------------

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