UnitOfWork synchronization bug?

Question

We're using UnitOfWork in our web application(OC4J 9.0.2 with the latest Toplink release 9.0.3.3).
In a "save" request, we register three different type of objects(three tables) in a uow.
Then we do a jmeter test with 10 the same "save" requests simultaniously. What the "save" does is two things:
(1) Do a query to retrieve a sequency Id
(2) Set the id to the first record and save the three records using UOW with the first record using id as the optimisticLock field.
The result:
2 successful saves,
1 error save ( saved the three correct objects and one extra from a different request)
The other 7, we got optimisticLockException and didn't save anything except one saved partially (which caused the error save mentioned above).
When we use ExternalTransactionController, we got "ValidationException" instead of OptimisticLockException. Other than that, it failed in a similar manner as the Toplink transaction controller did.
Is this a synchronization bug in our code or Toplink?
Anybody has similar experience or just my buggy code?
Thanks,
Wei

Answer 1

Don,
Here is my test:
In the "save", I save three records:
ARecord, BRecord, CRecord (Each has its own table)
and I also update a SequenceNumber record.
ARecord has a sequence number field and I uses "useChangedFieldsLocking" for optimistic locking for updating SequenceNumber object.
Here is the steps I do to "Save":
(1) get a client session and do a query on my sequence table to retrieve a sequence number in a SequencyNumber object
(2) Set the sequence id to ARecord
(3) Set some id related fields in BRecord,CRecord
(4) Register ARecord, BRecord and CRecord to a UOW
(5) Register the SequenceNumber I retrieved in Step (1) to UOW
(6) Increase the sequence in the SequenceNumber object
(7) commit
The optimistic locking works "all the time" if I use a single thread test.
In multiple thread condition, it works some times. When if failed, my result becomes:
for a ARecord here are the related saves:
ARecord, BRecord, BRecord, CRecord, CRecord
Some times I got three duplicates.
"Are you changing the pk of an object in a UOW?"
I don't think I changed the SequenceNumber object's pk.
I only changed one field value in my sequence table (not a key)
For the new objects, I do set their keys.
When I change my session to use External transaction controller:
serverSession.setExternalTransactionController(new Oracle9iJTSExternalTransactionController());
instead of getting a optimistic locking exception, I got this instead:
EXCEPTION [TOPLINK-7061] (TopLink - 9.0.3.3 (Build 430)): oracle.toplink.exceptions.ValidationException
EXCEPTION DESCRIPTION: Exception occurred within JTS.
INTERNAL EXCEPTION: javax.transaction.RollbackException
at oracle.toplink.exceptions.ValidationException.jtsExceptionRaised(Unknown Source)
at oracle.toplink.jts.JTSExternalTransactionController.commitTransaction(Unknown Source)
at oracle.toplink.publicinterface.Session.commitExternalTransaction(Unknown Source)
at oracle.toplink.publicinterface.UnitOfWork.commitInternallyStartedExternalTransaction(Unknown Source)
at oracle.toplink.publicinterface.UnitOfWork.commit(Unknown Source)
at icis.qci.db.QciInsert.insertToDB(QciInsert.java:50)
at icis.qci.common.CommonHttpHelper.commitFormJava(CommonHttpHelper.java:184)
at icis.qci.docket.QciDocketAction.executeProcess(QciDocketAction.java:97)
at icis.common.action.BaseCaseProcessAction.execute(BaseCaseProcessAction.java:84)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:484)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:274)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1480)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:506)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:195)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:309)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:336)
at com.evermind.server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:684)
at com.evermind.server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:269)
at com.evermind.server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:735)
at com.evermind.server.http.HttpRequestHandler.run(HttpRequestHandler.java:243)
at com.evermind.util.ThreadPoolThread.run(ThreadPoolThread.java:64)
Thanks for you help.
Wei