OConcurrentModificationException while creating relations between verticies

[vladmlch]

I created one instance of class Car with name "Mercedes" and want to create a relation between this car and two instances of class Person. Test throws an exception: OConcurrentModificationException. How can I avoid it and create as many edges as I want from many Persons to the same vertex Car?

Thanks, Vlad

    @Test
    public void testInsertFromDifferentThreads() throws InterruptedException {

    int threadsCount = 2;
    ExecutorService service = Executors.newFixedThreadPool(threadsCount);

    OrientGraph t1 = factory.graph();
    t1.begin();
    t1.getVerticesOfClass("Person").forEach(t1::removeVertex);
    t1.commit();

    t1.begin();
    OrientVertex mercedes = t1.addVertex("class:Car");
    mercedes.setProperty("name", "Mercedes");
    t1.commit();

    final CountDownLatch threadLatch = new CountDownLatch(threadsCount);
    final CountDownLatch mainLatch = new CountDownLatch(threadsCount);

    for (int i = 0; i < threadsCount; i++) {
        service.execute(() -> {
            ODatabaseDocumentTx tx = factory.openDatabase();
            ODatabaseRecordThreadLocal.INSTANCE.set(tx);

            OrientGraph t2 = factory.graph();
            t2.begin();

            OrientVertex luca = t2.addVertex("class:Person");
            luca.setProperty("name", "Luca");

            Vertex mercedes1 = t2.getVertices("Car.name", "Mercedes").iterator().next();
            luca.addEdge("Owns", mercedes1);

            threadLatch.countDown();
            try {
                threadLatch.await();
                t2.commit();
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            } finally {
                mainLatch.countDown();
            }
        });
    }
    mainLatch.await();

    assertEquals(threadsCount, t1.countVertices("Person"));
}

Stacktrace:

Exception in thread "pool-3-thread-1" com.orientechnologies.orient.core.exception.OConcurrentModificationException: Cannot UPDATE the record #32:2 because the version is not the latest. Probably you are updating an old record or it has been modified by another user (db=v62 your=v61)
at com.orientechnologies.orient.core.conflict.OVersionRecordConflictStrategy.checkVersions(OVersionRecordConflictStrategy.java:55)
at com.orientechnologies.orient.core.conflict.OVersionRecordConflictStrategy.onUpdate(OVersionRecordConflictStrategy.java:42)
at com.orientechnologies.orient.core.storage.impl.local.OAbstractPaginatedStorage.checkAndIncrementVersion(OAbstractPaginatedStorage.java:2020)
at com.orientechnologies.orient.core.storage.impl.local.OAbstractPaginatedStorage.doUpdateRecord(OAbstractPaginatedStorage.java:1657)
at com.orientechnologies.orient.core.storage.impl.local.OAbstractPaginatedStorage.commitEntry(OAbstractPaginatedStorage.java:2105)
at com.orientechnologies.orient.core.storage.impl.local.OAbstractPaginatedStorage.commit(OAbstractPaginatedStorage.java:917)
at com.orientechnologies.orient.core.tx.OTransactionOptimistic.doCommit(OTransactionOptimistic.java:483)
at com.orientechnologies.orient.core.tx.OTransactionOptimistic.commit(OTransactionOptimistic.java:147)
at com.orientechnologies.orient.core.db.document.ODatabaseDocumentTx.commit(ODatabaseDocumentTx.java:2376)
at com.orientechnologies.orient.core.db.document.ODatabaseDocumentTx.commit(ODatabaseDocumentTx.java:2346)
at com.orientechnologies.orient.server.network.protocol.binary.ONetworkProtocolBinary.commit(ONetworkProtocolBinary.java:1087)
at com.orientechnologies.orient.server.network.protocol.binary.ONetworkProtocolBinary.executeRequest(ONetworkProtocolBinary.java:389)
at com.orientechnologies.orient.server.network.protocol.binary.OBinaryNetworkProtocolAbstract.execute(OBinaryNetworkProtocolAbstract.java:220)
at com.orientechnologies.common.thread.OSoftThread.run(OSoftThread.java:69)

[vladmlch]

Is there any updates with this issue?

[lvca]

@profic This seems the classic case where you should manage the exception and retry. Isn't it?

[vladmlch]

Ok, now I catch an eception and retry again. When O run test for 1000 records, I get about 200 concurrent modification exception, but when I run test second time and try to add more edges and vertices, there are no exceptions at all and the version of single vertex to which I create edges does'n increment.

[tglman]

@profic this is due to the use of the (ridbag)[http://www.orientechnologies.com/docs/last/RidBag.html] if you set RID_BAG_EMBEDDED_TO_SBTREEBONSAI_THRESHOLD to 0 this should never happen but be aware that is a database settings and you may don't want this behaviour in other classes, just read the documentation for more info ;)