[Mulgara-general] NPE running embedded server at DEBUG log level - causes failure to start

Paul Gearon gearon at ieee.org
Mon Dec 12 16:44:08 UTC 2011

Hi Stephen,

Thanks for finding this. This bug is something left over from the days
of needing to debug the free list. Since it's worked correctly for so
many years now, no one has needed to run this class with debugging
enabled, so the bug was never triggered.

(I'll check in a patch shortly)

Was there a particular problem you were encountering with the free
list that required you to enable debugging, or are you just interested
to see how it works? The data structure and algorithm is obtuse, and
it isn't publicly documented. But I can help out if there's anything
you need.


On Mon, Dec 12, 2011 at 6:52 AM, Stephen Bayliss
<stephen.bayliss at acuityunlimited.net> wrote:
> When running the server embedded, it looks like there's an NPE that only
> occurs in DEBUG logging which is causing the server to fail to start.
> The culprit seems to be:
> org.mulgara.store.xa.FreeList.Phase
> Method: public sychronized Token use()
> If debug is enabled, it's doing a stack.add(new StackTace()) - but stack is
> set to null on construction (and not set anywhere else).  Liine 1147.
> Possibly another NPE due to the same cause around line 1242 (these from the
> 2.1.11 released source code).
> Regards
> Steve
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