[castor-dev] Concurrent Transaction Problems

[Keir Bowden]

Hi,

I am having a problem with concurrent Castor transactions from different machines accessing the same database.

I am using access="db-locked", as I have two jboss servers accessing the same datbase via Castor. However, I am still seeing the following error when both servers attempt to update the same object in the database :

--- snip ---

org.exolab.castor.jdo.ObjectModifiedException: Transaction aborted:
Object of type com.ilumin.dcx.entity.jdo.Message with identity
57,000 has been modified by a concurrent transaction

--- snip ---

It then goes on to say that the cached object does not match that in the database, even though I have also set <cache-type cache="none"/> in my mappings file.

After some further digging, it appears that this problem is occurring because I am retrieving the message objects from the database using Database.load(). The javadocs say that this method will take into account the type of locking being used, but this doesn't appear to be the case. If I change this to run an OQL query that selects from the database on object id, I get the behaviour that I expect. I've turned on full debugging and have noticed that the SQL for loading message objects doesn't have the "HOLDLOCK" hint that I would expect, but the OQL query generated select statement does.

I am using the latest Castor - 0.9.4.2 - has anyone else experienced this? Is this a known problem with Database.load().

Cheers

--

Keir Bowden
Olive Systems Limited
http://www.olive.co.uk

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