Finished my research of the ejb-core (3.0), jta (1.1) and jpa (2.0) specs
and found nothing, that guarantees these two behaviors.
So for me it looks like, that we rely on undefined behavior.
I might have overseen something, and if anyone knows more, I would
appreciate it, if you let me know.
Christian
On Fri, Jun 15, 2012 at 2:46 PM, Christian Romberg <cromberg_at_versant.com>wrote:
> Evan,
>
> You are right, the issue would not occur then.
>
> However so far I have been unsuccessful to find out, whether it is
> portable behavior, for the container to call Transaction.commit() while
> there are any XAResource enlisted with this Transaction, where start() had
> been invoked, but end() has not.
>
> Also I have not found out yet, whether there are scenarios, where the
> container must not delist the XAResource. (Although not
> directly applicable, the control flow diagram p.28/29 in the JTA spec
> suggests otherwise.)
>
> If both is defined, i.e. container does not delist XAResource it keeps in
> it's invocation context before calling Transaction.commit() and
> Transaction.commit() handles still enlisted resources fine (by calling
> beforeCompletion() first, calling end() after that, and then prepare+commit)
> then we (i.e. the JPA spec) would not have a problem.
>
> If anyone knows, that that is defined somewhere, please let me know, I
> will also continue researching the related specs.
>
> If that is not explicitly defined, than we (i.e. the JPA spec) do have a
> problem, because we rely on undefined behavior.
>
> Regards,
>
> Christian
>
>
> On Thu, Jun 14, 2012 at 10:31 PM, Evan Ireland <eireland_at_sybase.com>wrote:
>
>> Christian,
>>
>> In your step 6:
>>
>> "when the method invocation (of e.g. a session bean) ends, the container
>> will call Transaction.delistResource()"
>>
>> I wonder if that is the root of the difficulty.
>>
>> If the TM keeps JDBC connections (and/or XA resources) enlisted (in case
>> they are reused later in the same TX) until just before step 7b, then the
>> issue you are concerned about will not occur.
>>
>> > -----Original Message-----
>> > From: Christian Romberg [mailto:cromberg_at_versant.com]
>> > Sent: Friday, 15 June 2012 3:38 a.m.
>> > To: jsr338-experts_at_jpa-spec.java.net
>> > Subject: [jsr338-experts] question regarding JPA-JTA
>> > interaction (again)
>> >
>> > Dear group,
>> >
>> > While investigating and implementing our JTA integration, I
>> > came across the following problem for the standard
>> > implementation approach:
>> >
>> > 1. container starts a JTA transaction
>> > 2. createEntityManager is called, and registers a
>> > Synchronization instance
>> > 3. as soon as the EntityManager acquires a JDBC connection,
>> > the container gets the XAConnection from the connection pool,
>> > passes the result of XAConnection.getConnection() to the
>> > EntityManager and registers the result of XAConnection.getXAResource()
>> > with the current JTA transaction
>> > 4. the TM calls XAResource.start(xid, TMNOFLAGS);
>> > 5. all work done by the EntityManager with that connection
>> > happens in the context of the transaction (branch) denoted by xid now
>> > 6. when the method invocation (of e.g. a session bean) ends,
>> > the container will call Transaction.delistResource() which in
>> > turn will
>> > call XAResource.end(xid, TMSUCCESS) [mandated by JTA spec,
>> > JTA 1.1 sequence diagram on page 29]
>> > 7. Transaction.commit() will drive the
>> > 2-phase-commit-protocol, before invoking prepare and commit,
>> > all "beforeCompletion()" calls
>> > of registered Synchronization instances are invoked
>> > 7a. the beforeCompletion() implementation of the
>> > Synchronization instance registered in step 2 is supposed to
>> > flush all changes to the database
>> > 7b. XAResource.prepare(xid) is invoked
>> > 7c. XAResource.commit(xid) is invoked
>> >
>> > The problem ist step 7a: The connection is not associated
>> > with xid, so this simply does not work.
>> > Even if the connection is lazily acquired and released, there
>> > is no portable way to trigger the necessary
>> > start() and end() invocations by the JPA implementations.
>> >
>> > So how is this supposed to work?
>> >
>> > (Btw. we have direct control over our XAResource
>> > implementation, so we can trigger flushing by having a
>> > callback from our XAResource to
>> > our EntityManager during XAResource.end(), but this naturally
>> > is not an option, if a 3rd-party XAResource implementation is used.)
>> >
>> > Regards,
>> >
>> > Christian
>> >
>> > --
>> > Christian Romberg
>> > Chief Engineer | Versant GmbH
>> > (T) +49 40 60990-0
>> > (F) +49 40 60990-113
>> > (E) cromberg_at_versant.com
>> > www.versant.com
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>>
>
>
> --
> Christian Romberg
> Chief Engineer | Versant GmbH
> (T) +49 40 60990-0
> (F) +49 40 60990-113
> (E) cromberg_at_versant.com
> www.versant.com<http://www.google.com/url?q=http%3A%2F%2Fwww.versant.com%2F&sa=D&sntz=1&usg=AFrqEzeeEBc_gN_8mxtt8xDB0tjXDXQVlw>|
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>
>
> --
> Versant
> GmbH is incorporated in Germany. Company registration number: HRB
> 54723, Amtsgericht Hamburg. Registered Office: Halenreie 42, 22359
> Hamburg, Germany. Geschäftsführer: Bernhard Wöbker, Volker John
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--
Christian Romberg
Chief Engineer | Versant GmbH
(T) +49 40 60990-0
(F) +49 40 60990-113
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NOTICE: This e-mail message, including any attachments, is for the sole
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