Steve,
Is your usage multithreaded? If so, you'll need to make sure that usage
is mutlireaer or single writer.
Using jena transaction mecahnism is best - they work with datasets and
choose the best implementation for the datasets. For ones containing
inference, that's MRSW locking.
Another approach is to not reuse the inf model but to create a new one.
Any operation gets the model to work with from some AtomicReference<>.
Then outstanding threads finish what they are doing with the old setup
while new requests get the new view. Teh garbage collector wil reclaim
space sometime after all the outstanding old operatiosn have finished.
Andy
On 28/10/2021 13:26, Steve Vestal wrote:
Does anyone have any suggestions on things to try to avoid a
ConcurrentModificationException when using
OWLReasoner.OWL_MEM_MICRO_RULE_INF? Or what the potential consequences
of that are? (The below stack dump only goes back to where my code made
the call, the full one is fairly lengthy and full of Eclipse stuff as
well as mine. This is Jena 3.17.)
I am doing something a bit odd. There is one imported model that gets
reloaded from time-to-time, at the end of which I do an
ontModel.getBaseModel().rebind(). (The overall intent is sort of a
backwards base v schema workflow, where it is a small set of definitions
and axioms applied to the same big base model that get changed.) I get
this exception shortly after doing a reload/rebind, such as the first
one or few queries (as in this stackdump). After that things seem to
work OK. I only get the one exception after a reload/rebind. I'd still
like to (someday) understand what I'm doing, though.
Openllet/Pellet doesn't do this, but that is overkill and noticeably
slower for many workflows.
There is some punning done in the big base model, but works OK in many
workflows. This is the only case where I have seen anything other than
a few "not supported" warnings.
java.util.ConcurrentModificationException
at
org.apache.jena.reasoner.rulesys.impl.LPTopGoalIterator.checkCME(LPTopGoalIterator.java:248)
at
org.apache.jena.reasoner.rulesys.impl.LPTopGoalIterator.hasNext(LPTopGoalIterator.java:222)
at
org.apache.jena.util.iterator.WrappedIterator.hasNext(WrappedIterator.java:90)
at
org.apache.jena.util.iterator.WrappedIterator.hasNext(WrappedIterator.java:90)
at
org.apache.jena.util.iterator.FilterIterator.hasNext(FilterIterator.java:55)
at
org.apache.jena.util.iterator.WrappedIterator.hasNext(WrappedIterator.java:90)
at
org.apache.jena.util.iterator.FilterIterator.hasNext(FilterIterator.java:55)
at
org.apache.jena.sparql.engine.iterator.QueryIterTriplePattern$TripleMapper.hasNextBinding(QueryIterTriplePattern.java:143)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:74)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.iterator.QueryIterBlockTriplesStar.hasNextBinding(QueryIterBlockTriplesStar.java:54)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.iterator.QueryIterRepeatApply.makeNextStage(QueryIterRepeatApply.java:101)
at
org.apache.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:65)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.iterator.QueryIterConvert.hasNextBinding(QueryIterConvert.java:58)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:38)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:38)
at
org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:114)
at
org.apache.jena.sparql.engine.ResultSetStream.hasNext(ResultSetStream.java:74)
at
org.apache.jena.sparql.engine.ResultSetCheckCondition.hasNext(ResultSetCheckCondition.java:55)
at
com.adventiumlabs.fhowl.core.reasoner.StructuredClass.findReifiedStructure(StructuredClass.java:1231)
