Hi again, It's fixed I think. I was reading the model before starting the transaction... Sorry for the inconvenience.
On Tue, Nov 20, 2012 at 6:30 PM, Emmanuelle <[email protected]> wrote: > Hi all, > > I'm currently working on my master thesis that's related to tracking > students activities to provide adapted services and recommendations to > help their learning. I have implemented an ontology using Protege and > loaded it into a TDB directory. The ontology models students, learning > resources and stores the activity of the students on those resources > at a learning platform. In the background, the learning platform sends > those events to the ontology using a webservice interface implemented > in Axis which is the one accessing the TDB ontology for reading and > writing. > > I started to stress test sending concurrent requests to the webservice > and I'm getting concurrency errors as follow: > java.util.ConcurrentModificationException: Reader = 3, Writer = 1 > at > com.hp.hpl.jena.tdb.sys.DatasetControlMRSW.policyError(DatasetControlMRSW.java:157) > at > com.hp.hpl.jena.tdb.sys.DatasetControlMRSW.policyError(DatasetControlMRSW.java:152) > at > com.hp.hpl.jena.tdb.sys.DatasetControlMRSW.checkConcurrency(DatasetControlMRSW.java:79) > at > com.hp.hpl.jena.tdb.sys.DatasetControlMRSW.startRead(DatasetControlMRSW.java:46) > ...... > (versions listed at the end of this note) > > I understand that jena-TDB handles transactions and I'm using it in my > code, and on the other side, that the axis2 webservice is using a > single JVM with multiple threads (I hope not to be wrong on that one) > but it seems that TDB doesn't lock the dataset for writing. Can you > please confirm? Should I take care of locking? > > I've been searching this list and the internet for similar problems, I > have found several posts but couldn't find a solution for it. I'm new > to semantic web technologies, it's the first time I'm using jena and > TDB so probably I've missed something. Any help will be greatly > appreciated. > > Thanks in advance, > Emmanuelle > > Versions: > I've tried to update to jena-2.7.4 + tdb-0.9.4 but was getting errors > in tomcat with them so I gave up. > - jena-core-2.7.0-incubating > - jena-tdb-0.9.0-incubating > - pellet 2.3.0 > - java version "1.6.0_35": > Java(TM) SE Runtime Environment (build 1.6.0_35-b10) > Java HotSpot(TM) 64-Bit Server VM (build 20.10-b01, mixed mode) > - tomcat5.5.35 > - axis2 1.5.6
