The concurrency issue when using DbSqlSession to refresh CacheEntity to the database. about flowable-engine

[filiphr]

This works as designed.

What you have explained is valid optimistic lock that makes sure that Flowable stays in a consistent state. There is nothing wrong in the DbSqlSession since it is never been accessed concurrently from different threads.

The reason why you are seeing the optimistic locking exception is due to the fact that the second step is going to actually try and delete the "Share Task", this will trigger a deletion of the execution for the "NotCancelActivity" execution. However, in step 1 the "NotCancelActivity" will actually be deleted since it will be executed.

When the execution happens in the same time both threads are going to read REV_=1 for the "NotCancelActivity" execution. Depending on which thread finishes first there would either be an optimistic lock exception on the first or the second step.

If Step 1 finishes first, then in Step 2 when trying to delete "NotCancelActivity" it will try to delete the execution with the appropriate id and revision 1. However, that execution no longer exists and thus an optimistic lock exception is thrown.

If Step 2 finishes first, then in Steps when trying to delete the "Share Task" and its associated "NotCancelActivity" execution, a similar thing happens. There is no execution for "NotCancelActivity" anymore and thus there is an optimistic lock exception.

Since this works as designed we are going to close this. However, feel free what you think should happen and how an optimistic locking exception can be avoided here.