Optimistic locking failure

Optimistic locking failure:

I am using a Semaphore to force this execution of concurrents transactions T1 and T2 that cause parallel updates to A/B but it does not throw an OptimisticLockException and roll back.

           T1                           T2
----------------------------------------------------------
READ(A) version=1 value=0   |
READ(B) version=1 value=0   |
                             | READ(A)  version=1 value=0
                             | READ(B)  version=1 value=0
                             | B = A + B + 20
                             | WRITE(B) version=2 value=20
A = A + B + 10              |
WRITE(A) version=2 value=10 |
-----------------------------------------------------------
Results A: version=2 value=10, B: version=2 value=20

Thanks.

Please explain the test output:

Sequential=true Lock=WRITE
Thread[Thread-2,5,main] READ  A1 version=1 value=0
Thread[Thread-2,5,main] READ  B2 version=1 value=0
Thread[Thread-2,5,main] WRITE A1 version=2 value=10
Thread[Thread-3,5,main] READ  A1 version=2 value=10
Thread[Thread-3,5,main] READ  B2 version=1 value=0
Thread[Thread-3,5,main] WRITE B2 version=2 value=30
A1 version=2 value=10, B2 version=2 value=30

Sequential=false Lock=WRITE
Thread[Thread-6,5,main] READ  A1 version=1 value=0
Thread[Thread-6,5,main] READ  B2 version=1 value=0
Thread[Thread-6,5,main] WRITE A1 version=2 value=10
Thread[Thread-7,5,main] READ  A1 version=2 value=10
Thread[Thread-7,5,main] READ  B2 version=1 value=0
Thread[Thread-7,5,main] WRITE B2 version=2 value=30
A1 version=2 value=10, B2 version=2 value=30

• There are 2 runs. Which one demonstrates the issue? the sec
• According to the output in both cases the execution of the threads is sequential, so exception is not expected. Please explain the problem.

Please try this new version attached,  the output would be something like this:

Thread[Thread-1,5,main] READ  A1 version=1 value=0
Thread[Thread-1,5,main] READ  B2 version=1 value=0
Thread[Thread-2,5,main] READ  A1 version=1 value=0
Thread[Thread-2,5,main] READ  B2 version=1 value=0
Thread[Thread-2,5,main] WRITE B2 version=2 value=20
Thread[Thread-1,5,main] WRITE A1 version=2 value=10
A1 version=2 value=10, B2 version=2 value=20

Thanks.

Thank you for the revised test that demonstrates the issue well.

Please try build 2.3.7_23 that should throw an exception in this case.

It would be great if was fixed the same problem with LockModeType.READ:

Thread[Thread-1,5,main] READ  A1 version=1 value=0
Thread[Thread-1,5,main] READ  B2 version=1 value=0
Thread[Thread-2,5,main] READ  A1 version=1 value=0
Thread[Thread-2,5,main] READ  B2 version=1 value=0
Thread[Thread-2,5,main] WRITE B2 version=2 value=20
Thread[Thread-1,5,main] WRITE A1 version=2 value=10
A1 version=2 value=10, B2 version=2 value=20

Thanks.

You are right again. To support this, starting build 2.3.7_24 OPTIMISTIC (READ) is implemented as OPTIMISTIC_FORCE_INCREMENT (WRITE). This is allowed by JPA, and is required by ObjectDB in order to identify this conflict that your test demonstrates.