On 17/05/11 14:53, Frank Budinsky wrote:
Hi guys,
Hi Frank,
Your code looks OK but the error message implies there is another thread
about (it looks like the other thread is doing a write (includes sync) -
the stacktrace shows the code is doing a read at this point).
TDB throws ConcurrentModificationException as a checking operation.
it's not connected with locks directly but exists to check locks are
being used for MRSW. So "Reader = 1" is this thread, and "Writer = 1"
is something else.
Andy
I'm getting the following exception sometimes:
java.util.ConcurrentModificationException: Reader = 1, Writer = 1
at com.hp.hpl.jena.tdb.sys.ConcurrencyPolicyMRSW.policyError
(ConcurrencyPolicyMRSW.java:132)
at com.hp.hpl.jena.tdb.sys.ConcurrencyPolicyMRSW.policyError
(ConcurrencyPolicyMRSW.java:127)
at com.hp.hpl.jena.tdb.sys.ConcurrencyPolicyMRSW.checkConcurrency
(ConcurrencyPolicyMRSW.java:64)
at com.hp.hpl.jena.tdb.sys.ConcurrencyPolicyMRSW.startRead
(ConcurrencyPolicyMRSW.java:31)
at com.hp.hpl.jena.tdb.nodetable.NodeTupleTableConcrete.startRead
(NodeTupleTableConcrete.java:60)
at com.hp.hpl.jena.tdb.nodetable.NodeTupleTableConcrete.findAsNodeIds
(NodeTupleTableConcrete.java:132)
at com.hp.hpl.jena.tdb.store.TripleTable.find(TripleTable.java:71)
at com.hp.hpl.jena.tdb.store.GraphTDBBase.graphBaseFindWorker
(GraphTDBBase.java:115)
at com.hp.hpl.jena.tdb.store.GraphTriplesTDB.graphBaseFind
(GraphTriplesTDB.java:61)
at com.hp.hpl.jena.sparql.graph.GraphBase2.find(GraphBase2.java:232)
at com.hp.hpl.jena.sparql.graph.GraphBase2.graphBaseFind
(GraphBase2.java:253)
at com.hp.hpl.jena.sparql.graph.GraphBase2.find(GraphBase2.java:249)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.listStatements
(ModelCom.java:378)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.listStatements
(ModelCom.java:383)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.getProperty
(ModelCom.java:1003)
at com.ibm.lld.store.TDBMetadataStore.storeCurrentETag
(TDBMetadataStore.java:75)
I believe I'm correctly acquiring a WRITE lock. This is the failing code in
my class TDBMetadataStore:
public void storeCurrentETag(String resourceURI, String etag)
{
fResourceDataset.getLock().enterCriticalSection(Lock.WRITE);
try {
Model model = fResourceDataset.getDefaultModel();
Resource resource = model.getResource(resourceURI);
LINE 75 --> Statement etagStmt = model.getProperty(resource, IndexMeta.
ETag);
Shouldn't it be impossible to get to line 75, while there's an outstanding
Reader?
I'm using the latest TDB release (0.8.10). Any ideas what could be causing
this?
Thanks,
Frank.
