But then again, I cannot lock what I don't have: locks work on models, and I only get OntModel instance when getOntology() is called.
Maybe synchronized is the solution here? On Sun, 17 Jul 2016 at 15:32, Martynas Jusevičius <marty...@graphity.org> wrote: > Thanks Andy. > > All of our code except OntDocumentManager access uses imutable objects, so > I hope to keep lock usage to an absolute minimum. Transactions look like an > overkill at this point. > > So if getOntology() is a write operation, if I wrap only this piece of > code where it is called into a WRITE critical section, wouldn't that be > enough? > > I think the docs lack an explanation on which ops are read and which are > write. > > On Sun, 17 Jul 2016 at 12:22, Andy Seaborne <a...@apache.org> wrote: > >> Better: transactions (3.1.0) >> >> http://jena.staging.apache.org/documentation/txn/transactions.html >> >> We now have a fully ACID transactional in-memory graph (TIM) as well as >> TDB. >> >> The "Txn" highlevel API is not in the released codebase. >> >> http://jena.staging.apache.org/documentation/txn/txn.html >> >> Planning now for transactions should make things a lot easier later. >> >> Andy >> >> On 16/07/16 16:03, Martynas Jusevičius wrote: >> > On a second thought, since our code is only reading from the models, it >> is >> > probably easier and safer just to clone the shared model into a >> per-request >> > copy, and keep the code as it is. >> >> If the shared model is only ever read, you can share it. >> >> (getOntology isn't a read operation.) >> >> > >> > Is the following code the fastest way to do it? Is add() expensive? >> > >> > >> > OntModel ontModel = >> > OntDocumentManager.getInstance().getOntology(ontologyURI, ontModelSpec); >> > OntModel clonedModel = ModelFactory.createOntologyModel(ontModelSpec); >> > clonedModel.add(ontModel); >> > >> > >> > On Sat, Jul 16, 2016 at 3:47 PM, Martynas Jusevičius < >> marty...@graphity.org> >> > wrote: >> >> Hey, >> >> >> >> in our webapp, all objects are created per-request, except ontologies >> >> stored in a shared OntDocumentManager, that are accessed like this: >> >> >> >> OntDocumentManager.getInstance().getOntology(ontologyURI, >> ontModelSpec); >> >> >> >> This has caused some ConcurrentModificationExceptions. >> >> I have read the >> >> https://jena.apache.org/documentation/notes/concurrency-howto.html >> >> document, and wanted to check if I get this right. >> >> >> >> Basically, every operation and iterator on a shared OntModel has to be >> >> in a critical section? Even if it's indirect and called on an OntClass >> >> from the OntModel: >> >> >> >> OntModel ontModel = >> >> OntDocumentManager.getInstance().getOntology(ontologyURI, >> >> ontModelSpec); >> >> ontModel.enterCriticalSection(Lock.READ); >> >> try >> >> { >> >> OntClass ontClass = ontModel.getOntClass("http://some/class";); >> >> NodeIterator it = ontClass.listPropertyValues(GC.supportedMode); >> >> try >> >> { >> >> while (it.next) >> >> ... >> >> } >> >> finally >> >> { >> >> it.close(); >> >> } >> >> } >> >> finally >> >> { >> >> model.leaveCriticalSection() ; >> >> } >> >> >> >> Is that correct? >> >> >> >> Martynas >> > >> >>
