Re: Concurrent access to a shared (Ont)Model

[Andy Seaborne]

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