Hi Mike,
Yep, I knew that, the problem really is, that it does not guarantee a
non-delistment in our scenario.
The
"TransactionSynchronizationRegistry.registerInterprosedSynchronization()"
is a good indication, however it only
addresses one of the many requirements, which must be standardized.
I explained the problem to the JTA 1.2 group, and also suggested, that
after addressing these issues, that
they include a control-flow diagram for the JPA-JTA interaction as well.
Regards,
Christian
On Mon, Jun 18, 2012 at 10:11 PM, michael keith <michael.keith_at_oracle.com>wrote:
> Hi Christian,
>
> A few comments.
>
> The process described in the JTA spec on page 28 is illustrative, not
> prescriptive, so there is no requirement for the app server to delist the
> resource. That was just an example walkthrough of what *could* happen when
> a client closed a connection. I think you probably already knew that,
> though, because I think your point was just that if that *could* happen
> then it could break a JPA EM that wanted to write to the connection later
> on? Although, container data sources all pool the connections so in
> practice the connections never get closed, anyway (so the above case does
> not ever really occur).
>
> Perhaps the strongest case is that the
> TransactionSynchronizationRegistry.registerInterprosedSynchronization()
> method in the JTA spec actually does state that beforeCompletion callback
> methods can access the resources, but that no transactional work can be
> performed on resources in afterCompletion. I would say that since the app
> server must provide this semantic we might be able to say that we are on
> reasonably firm ground. Would you agree?
>
> -Mike
>
>
> On 15/06/2012 9:56 AM, Christian Romberg wrote:
>
> 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 <%2B49%2040%2060990-0>
>>> > (F) +49 40 60990-113 <%2B49%2040%2060990-113>
>>> > (E) cromberg_at_versant.com
>>> > www.versant.com
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>>> > &sntz=1&usg=AFrqEzdo3Q40RwKQPBtnPIuBYQd1diFxJQ>
>>> >
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>>> > GmbH is incorporated in Germany. Company registration number: HRB
>>> > 54723, Amtsgericht Hamburg. Registered Office: Halenreie 42, 22359
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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>|
>> www.db4o.com<http://www.google.com/url?q=http%3A%2F%2Fwww.db4o.com%2F&sa=D&sntz=1&usg=AFrqEzdo3Q40RwKQPBtnPIuBYQd1diFxJQ>
>>
>>
>> --
>> 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
>>
>> CONFIDENTIALITY
>> NOTICE: This e-mail message, including any attachments, is for the sole
>> use of the intended recipient(s) and may contain confidential or
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>> distribution is prohibited. If you are not the intended recipient,
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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
>
> CONFIDENTIALITY
> NOTICE: This e-mail message, including any attachments, is for the sole
> use of the intended recipient(s) and may contain confidential or
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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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--
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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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NOTICE: This e-mail message, including any attachments, is for the sole
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