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From John Embretsen <John.Embret...@Sun.COM>
Subject Re: Derby causes PermGen leaks in Tomcat
Date Tue, 25 Sep 2007 14:15:15 GMT
Alan Burlison wrote:
>> Derby objects are still loaded, and jstack shows several instances of 
>> this:
>>
>> "derby.antiGC" daemon prio=1 tid=0x088e7000 nid=0xd in Object.wait() 

>> So it's clear that although the Derby server is stopped, it's still 
>> zombified somewhere inside the Tomcat JVM.  How do I cleanly and 
>> completely remove Derby from a running JVM?
> 
> I found this thread that looked relevant: 
> http://www.nabble.com/RE%3A-AntiGC-Not-Shutting-Down-p1217286.html
> 
> "Shutting down the databases before shutting down the server has solved 
> all of my problems."
> 
> I've modified my code to do the same, and I've even tried explicitly 
> unloading the Derby JDBC driver, but I still get an instance of AntiGC 
> hanging around, although all the other Derby threads do terminate.

I haven't seen any details of how you unload the embedded driver, but have you 
tried shutting down the Derby system explicitly as well as (or instead of) 
shutting down the particular database?

When I run a small test case (outside of Tomcat) I see the AntiGC thread hanging 
around after doing:
  - load embedded driver (with newInstance())
  - start the network server using the NetworkServerControl API
  - shutdown database (example URL: "jdbc:derby:leakDB;shutdown=true")
  - shutdown server (netServerControl.shutdown())

However, when I do:
  - load embedded driver (with newInstance())
  - start the network server using the NetworkServerControl API
  - shutdown Derby system (example URL: "jdbc:derby:;shutdown=true")
  - shutdown server (netServerControl.shutdown())

I don't see the AntiGC thread (using jstack).

PermGen space usage seems to be fairly stable  at around 11-12 MB even after 
several hundred iterations of either of the scenarios mentioned above, so I'm 
not able to reproduce your case outside Tomcat (please post if you are!). I 
suspect Tomcat may be a part of the problem here...


-- 
John



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