Context: Hibernate 2.1.4 + JBoss 3.2.3 + MySQL

Goal: to perform XA (distributed transaction) over 2 Hibernate sessions, each session connected to a different data source.

Both the datasources are local-tx-datasources since the MySQL Connector/J driver does not support XA.

Thus, I am getting a Warning as specified in this wiki item
http://www.jboss.org/wiki/Wiki.jsp?page ... MSWithJDBC

I want to know of some way to simulate 2PC. My idea is to create maintain my own transaction logs, one each for HibernateSession1 & HibernateSession2. I would do a flush on both sessions. If no exceptions are thrown, all is well. If I get some exceptions, I will try to simulate a rollback by reversing the steps in the transaction logs. I'd probably place the logs in a static ThreadLocal. My understanding is that when you call session.flush(), it is persisted to the DB and no explicit tx.rollback() will revert it to the previous state.

Qu'en pensez-vous ?

A

Alister,

I guess nobody has replied to this because it just doesn't sound like a good idea (well not to me anyway).

Upgrading your JBoss to 3.2.6 will fix the warning. If you need 2PC then you should move to a database that supports it. Building these sort of things yourself is very difficult and adds considerable overhead to your application. Your solution may also fail under obscure conditions (what happens if your roll back fails for instance).

Firebird http://firebird.sourceforge.net/ is one suggestion. It is a real database with full XA transaction support. Online support is also good via its mailing lists.

David

Let's suppose you commited first DS. Then got error commiting second and you're going to rollback by hands first DS. So the data that was commited and maybe already used by someone else will magically disappear. In the worst case, some could have already changed that data so it will be lost forever. This is absolutely inappropriate and it's what XA about.



No, session.flush() executes SQL statement against DS. if you're in TX calling tx.rollback() will revert the previous state (in fact, state is never changed unless it's commited).

David is right, if you need XA just use DS which supports it.

PS instead of writing hibernate XA emulation for MySQL maybe you can write XA support for MySQL itself?