Re: [Springframework-developer] Hibernate resource management issue

[<jue...@we...>]

Colin,
=20
Thanks for tracking this down. It's actually a problem with =
SessionFactoryUtils' inner class SessionSynchronization: It assumes that =
beforeCompletion is called in any case, even if beforeCommit has thrown =
an exception. However, this just applies if you specified a =
TransactionManagerLookup in the Hibernate configuration; else, =
afterCompletion will do the cleanup - which will be called in any case.
=20
When you remove the Hibernate TransactionManagerLookup, you shouldn't =
face the issue - the bug doesn't have any effects then. Note that you =
don't need that TransactionManagerLookup when using Spring's =
JtaTransactionManager, as Spring will properly apply cache callbacks =
anyway. A TransactionManagerLookup just adds value when used with EJB =
CMT or manual JTA, for ultra-correct cache callbacks.
=20
So essentially, everything should be fine if using =
HibernateTransactionManager, or JtaTransactionManager without a =
Hibernate TransactionManagerLookup. This is clearly something to fix, =
but I guess we don't need to do an immediate 1.0.1 followup release; I'd =
like to gather further bug reports first. For the time being, let's =
suggest to remove the TransactionManagerLookup from the Hibernate =
configuration.
=20
Juergen
=20

________________________________

Von: Colin Sampaleanu [mailto:col...@ex...]
Gesendet: Do 25.03.2004 20:32
An: spr...@li...; j=FCrgen h=F6ller =
[werk3AT]
Betreff: Re: [Springframework-developer] Hibernate resource management =
issue



Juergen,

I am almost 100% sure this block of code from
AbstractPlatformTransactionManager is wrong:
        else {
            try {
                try {
                    triggerBeforeCommit(defStatus);
                    triggerBeforeCompletion(defStatus);
                    if (status.isNewTransaction()) {
                        logger.info("Initiating transaction commit");
                        doCommit(defStatus);
                    }
                }
                catch (UnexpectedRollbackException ex) {
                    triggerAfterCompletion(defStatus,
TransactionSynchronization.STATUS_ROLLED_BACK, ex);
                    throw ex;
                }
                catch (TransactionException ex) {
                    if (this.rollbackOnCommitFailure) {
                        doRollbackOnCommitException(defStatus, ex);
                        triggerAfterCompletion(defStatus,
TransactionSynchronization.STATUS_ROLLED_BACK, ex);
                    }
                    else {
                        triggerAfterCompletion(defStatus,
TransactionSynchronization.STATUS_UNKNOWN, ex);
                    }
                    throw ex;
                }
                catch (RuntimeException ex) {
                    doRollbackOnCommitException(defStatus, ex);
                    triggerAfterCompletion(defStatus,
TransactionSynchronization.STATUS_ROLLED_BACK, ex);
                    throw ex;
                }
                catch (Error err) {
                    doRollbackOnCommitException(defStatus, err);
                    triggerAfterCompletion(defStatus,
TransactionSynchronization.STATUS_UNKNOWN, err);
                    throw err;
                }
                triggerAfterCompletion(defStatus,
TransactionSynchronization.STATUS_COMMITTED, null);
            }
            finally {
                cleanupAfterCompletion(defStatus);
            }
        }

triggerBeforeCommit() execute, which in the Hibernate case will force a
flush. However, if that flush throws an exception, then
   triggerBeforeCompletion(defStatus);
never gets called. However, triggerBeforeCompletion is what is actually
supposed to release the Hibernate session holder from the current
thread! So in this case, the session (which is totally hosed of course),
gets left on the thread. I believe in some environments this wouldn't
matter that much, as the threads don't get resused. In the JBoss case,
new requests coming in will get the existing thread, and this time,
SessionFactoryUtils will see the session is there, and try to use it.
Bang, it all blows up...

So for this code to work properly, what needs to happen is that
triggerBeforeCompletion still needs to be called even if
triggerBeforeCommit fails. While I am ok with writing the code in this
method to handle this, I am not 100% sure this is safe in terms of all
the other interactions that will happen as a result; mot of this code is
your baby with me only having traced through it once in a while. So if
you would prefer to resolve this that would be great.

Unless I am mistaken about this bug, I think it is a pretty serious one,
and warrants an almost immediate release of a v1.0.1 of Spring...

Regards,
Colin


Colin Sampaleanu wrote:

> I am tracking down a possible Hibernate resource management issue.
>
> In a running app, some time yesterday, some code, running in a wrapped
> transaction with Hibernate handling ORM, encountered an Oracle
> constraint violation and threw an exception. Fine...
>
> But when I log into the app myself now via the web ui and then it gets
> a service object to read some data, the service object is wrapped with
> a transaction interceptor, and also a hibernate interceptor. The
> Hibernate interceptor is already seeing a Hibernate Session existing
> on the current thread, so it is not creating a new one. Then at the
> end of the transaction, when the Hibernate session is attempted to be
> flushed, Hibernate tries to write out the old bad data from yesterday.
>
> What this essentially means is that when the error from yesterday
> happened, the session did not get released from the thread, and has
> been sticking around all this time. When I came via struts, I was
> given the same thread as yesterday by the appserver, and the old
> invalid session was still on it. The problem is not that it's reusing
> that session, but why it was ever left that the day before.
>
> Will try to duplicate this...