Memory Leak

[Emilio Miguelanez]

Hi list,

I have developed a jena-based application, which has a TDB back-end which loads 
a owl file with some good number of triples. All using the Jena API.

I have done some testing (1000 queries every second), and I get a memory leak 
on com.hp.jena.graph.Node_Literal. 

The stack is as follows


Currently 470 leaked objects exist of class
        com.hp.hpl.jena.graph.Node_Literal

The objects are created at
        com.hp.hpl.jena.graph.Node$2.construct(java.lang.Object):238

and are being held 
        in nodes of com.hp.hpl.jena.graph.NodeCache
                in present of com.hp.hpl.jena.graph.Node
                        in elementData of java.util.Vector
                                in classes of sun.misc.Launcher$AppClassLoader


The leak is not that huge (101K of the total available 77M heap), but it is a 
leak. It starts to show up half-way through the testing session. So I am 
assuming that a leaked object is created every time a query is executed. The 
query is being done in the following fn:

public static String printSelectQueryAsJSON(Model model, String queryString)
            throws QueryExecException, QueryParseException, IOException, 
ConcurrentModificationException {

        String queryResults = null;

        Query query = QueryFactory.create(queryString, Syntax.syntaxARQ);

        if (!query.isSelectType()) {
            throw new QueryExecException("Attempt to execute a SELECT query 
from a " + QueryEngineUtils.labelForQuery(query) + " query");
        }

        QueryExecution qexec = QueryExecutionFactory.create(query, model);

        //qexec.getContext().set(TDB.symLogExec, Explain.InfoLevel.FINE);

        ByteArrayOutputStream out = new ByteArrayOutputStream();

        try {
            ResultSet results;
            results = qexec.execSelect();

            ResultSetFormatter.outputAsJSON(out, results);
            queryResults = out.toString();
            
        } finally {
            qexec.close();
            out.flush();
        }
        
        long epoch_ends = System.currentTimeMillis();
        logger.debug("QET (" + lQueryId + "): " + (epoch_ends - epoch_starts));

        return queryResults;
    }


For extra info, the set of libraries I am using is:

Jena 2.6.4
ARQ-2.8.8
TDB-0.8.10


Any idea where I should start looking to solve this memory leak will be useful.

Thanks in advance,
Emilio