[Glass] instances not being garbage collected?

[Dale Henrichs]

Johan,

Two thing come to mind right off the bat:
  1. did these objects participate in an index?
  2. have you cycled all of your gems recently

If you are using indexes, strong references to objects will be made from
the DepMap (an ObjectTable-like entity that maps objects to their
dependents for modification tracking). Objects are managed correctly with
respect to the DepMap, however, if you drop a reference to a collection
that has an index without first removing the index, the DepMap will keep
objects alive. If you are not using indexes the DepMap should be empty.

Long running gems may end up keeping references to otherwise dead objects
[1], especially if you haven't haven't set  GEM_TEMPOBJ_POMGEN_PRUNE_ON_VOTE
to something like 90:

GEM_TEMPOBJ_POMGEN_PRUNE_ON_VOTE=90;

in your system.conf. Even with the above, you are not guaranteed to prune
all of the persistent references on the vote. You should be suspicious that
you are seeing this particular problem if you consistently see a high
number of possible dead in your mfc report. Also look at vsd and after an
mfc you should see the stone stat PossibleDeadObjs jump up to the value
that was reported when your mfc ran ... Then a short while later (after
voting is complete) you should see the stone stat DeadNotReclaimedObjs jump
... if DeadNotReclaimedObjs is significantly less than PossibleDeadObjs,
then those objects were "voted down" because one or more live gems had a
reference to the object in its head. If you've already got
GEM_TEMPOBJ_POMGEN_PRUNE_ON_VOTE
set to 90 you might try cycling all of your gems and run another mfc ....

If your PossibleDeadObjs from an mfc is not as high as you think it should
be, then I will have to do some more research on finding out if there are
any other "hidden" references to objects ...

Dale

[1] https://code.google.com/p/glassdb/issues/detail?id=136


On Mon, Jan 20, 2014 at 11:40 AM, Johan Brichau <johan at yesplan.be> wrote:

> Hi,
>
> My repository has a (large) number of objects that are no longer
> referenced from the persistent root but that are never garbage collected.
>
> When I do:
>
>         ClassXX allInstances
>
> I get a number of instances but when I then do for an instance i:
>
>         SystemRepository findReferencePathForObject: i
>
> The answer is that there is no path (aka 'false' as the second element in
> the array that is returned).
>
> Any ideas how I can investigate this?
>
> thx
> Johan
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