Hi,
Now that I'm busy with implementing our own transaction manager (and
eventually application server) for our test environment,
I stumbled across a new issue, that is an argument pro-JDBC pool and
against direct TM interaction:
There seems to be no standard way, how to restore XAResources after a
system failure, which is a short-coming of the JTA spec.
The described way there suggests, that the TM logs JNDI names in it's
transaction log records, which only works, if the pull-approach
was used via a JDBC pool (or JCA based pool).
However e.g. JBoss handles that properly, if the XAResource is
Serializable, it will serialize it (so we will make our XAResource
serializable)
But for other app servers this might not work, and a fake JDBC pool would
solve it for those.
We will still go for direct TM interaction, especially since JBoss supports
XAResource serialization.
Regards,
Christian
On Tue, May 15, 2012 at 9:26 AM, Christian Romberg <cromberg_at_versant.com>wrote:
> Hi Pinaki,
>
> As I pointed out, it would only be a "fake" JDBC driver, I know, that the
> TM does not care, what type of resource is behind the XAResource,
> it's just that we need to enlist our XAResource with the current
> transactions.
> Either the app server picks it up itself (pull-approach, via a fake JDBC
> driver, or -in theory- a JCA adapter) or we enlist it directly
> (push-approach)
>
>
> > In effect, I do not see why a non-JDBC based JPA provider has to appear
> as a JDBC connection to a application server to participate in a JTA
> transaction.
>
> Two simple reasons:
> -app servers do support JDBC connection pools and JCA is not a viable
> approach
> -there is no standard way to get access to the TransactionManager (however
> there is a standard way to get the TransactionSynchronizationRegistry,
> which is sufficient
> for other JPA implementations)
>
> However we will probably still use the alternative, to enlist our
> XAResource directly with the TransactionManager.
>
> So we will do some probing in the code, to find out which app server we
> are in and/or try out a list of well-known JNDI-names
> to look-up the TransactionManager.
>
> Regards,
>
> Christian
>
>
> On Mon, May 14, 2012 at 7:11 PM, Pinaki Poddar <ppoddar_at_us.ibm.com> wrote:
>
>> Christian,
>> In a JPA environment, a JPA Persistence Unit registers as a transactional
>> resource to the application server's global transaction management
>> coordination system via JTA standard i.e. by caling
>> javax.transation.registerSynchronization(x) where x is something that a
>> provider provides which implements javax.transaction.Synchronization. In a
>> non-JDBC JPA provider like yours, you will possibly pass an instance of
>> persistence context i.e EntityManager as x.
>> For an application server transaction management sevices, all it knows is
>> x whether x is using an underlying JDBC or non-JDBC database is not
>> relevant. So essentially the provider will receive a beforeCompletion()
>> call from application server when time comes to commit the global
>> transaction via x because x is a registered Synchronization object. At
>> beforeCompletion(), the provider is responsible to commit on the underlying
>> database be it JDBC or somethiing else.
>>
>> If a provider's persistence unit is also XA-enabled that capability is
>> communicated by a) implementing javax.transaction.xa.XAResource and b)
>> enlisting that resource to the application server. A resource, in this
>> case, is the persistence unit, not the jta-data-source as declared in
>> persistence.xml.
>>
>> In effect, I do not see why a non-JDBC based JPA provider has to appear
>> as a JDBC connection to a application server to participate in a JTA
>> transaction.
>>
>>
>> > I think I forgot to emphasize, that we are not an ORM and are not using
>> JDBC connections.
>> I did notice that :)
>>
>>
>> Regards --
>>
>> Pinaki Poddar
>> Chair, Apache OpenJPA Project http://openjpa.apache.org/
>> JPA Expert Group Member
>> Application & Integration Middleware
>>
>>
>>
>>
>>
>>
>> [image: Inactive hide details for Christian Romberg ---05/14/2012
>> 01:17:26 AM---Hi Michael and Pinaki, Yes, I understood how this is su]Christian
>> Romberg ---05/14/2012 01:17:26 AM---Hi Michael and Pinaki, Yes, I
>> understood how this is supposed to work, however this does not and
>>
>> From: Christian Romberg <cromberg_at_versant.com>
>>
>> To: michael keith <michael.keith_at_oracle.com>
>> Cc: jsr338-experts_at_jpa-spec.java.net
>> Date: 05/14/2012 01:17 AM
>> Subject: [jsr338-experts] Re: question regarding jta-data-source
>> ------------------------------
>>
>>
>>
>> Hi Michael and Pinaki,
>>
>> Yes, I understood how this is supposed to work, however this does not and
>> can not work for us this way out-of-the box.
>>
>> I think I forgot to emphasize, that we are not an ORM and are not using
>> JDBC connections.
>>
>> Of course we can (and would) register a Synchronization object with the
>> global transaction.
>>
>> But where should the container get the XAResource from? Because we are
>> not using JDBC connections, which implies, we
>> are not using any DataSource. So there is simply no way for the app
>> server to drive the XA protocol.
>>
>> Unless of course, we would provide a "fake" XADataSource in a "fake" JDBC
>> driver, and given the pseudo-code assumption
>> from my previous mail, we would then just call "getConnection()" on the
>> jta-data-source (which points to an app server pool
>> configured with our "fake" JDBC driver, configured to return enlisted
>> connections) and don't actually use the result
>> of the "getConnection()" invocation (which is a dummy implementation
>> anyways)
>>
>> I'm pretty sure, that my pseudo-code assumption is correct, mostly
>> because I can not think of any other straight-forward
>> (or even weird) way how to implement that in the app server.
>>
>> So this would be the way to go for us.
>>
>> Regards,
>>
>> Christian
>>
>> On Fri, May 11, 2012 at 10:45 PM, michael keith <*
>> michael.keith_at_oracle.com* <michael.keith_at_oracle.com>> wrote:
>>
>> Hi Christian,
>>
>> Yes, that's pretty much how it works.
>>
>> -Mike
>>
>>
>> On 11/05/2012 9:45 AM, Christian Romberg wrote:
>> Hi Mike,
>>
>> Unlike ORMs, we need to provide the XAResource instances to the
>> app server
>> (which in turn are associated with our internal connections to the
>> database server)
>>
>> But I guess, if the user just sees a DataSource, then that will be
>> an app server proxy which eventually delegates to the XADataSource of
>> our "JDBC" driver (provided I configure a DataSource that returns
>> enlisted connection in the app server using our JDBC driver)
>>
>> So my pseudo-code assumption of the app servers DataSource proxy
>> is like this:
>>
>> public class ContainerDataSourceProxy implements DataSource {
>>
>> XADataSource xaDs = ...; //XADataSource of the installed
>> JDBC driver for this pool
>>
>> public Connection getConnection() throws SQLException {
>> XAConnection xaCon = xaDs.getXAConnection();
>> enlist(xaCon.getXAResource());
>> return xaCon.getConnection();
>> }
>> ...
>> }
>>
>> So we could simply call getConnection() (and not using the
>> returned value at all) to trigger the app servers
>> enlisting our XAResource.
>>
>> Regards,
>>
>> Christian
>>
>> On Fri, May 11, 2012 at 3:14 PM, michael keith <*
>> michael.keith_at_oracle.com* <michael.keith_at_oracle.com>> wrote:
>> Hi Christian,
>>
>> The data source referenced by the jta-data-source name is a
>> DataSource provided by the container in JNDI. It is the same one that any
>> application could look up and use, hence it is a javax.sql.DataSource.
>>
>> XADataSource is an internal type used by the driver and
>> container to coordinate XA, but users of the data source are not expected
>> to participate at that level. The JPA provider acts like a client of the
>> data source, using its connections to read and write, so it does not need
>> to be aware of the XA protocol being implemented underneath.
>>
>> Hope this makes things clearer.
>>
>> Regards,
>> -Mike
>>
>>
>> On 10/05/2012 7:50 AM, Christian Romberg wrote:
>> Hello,
>>
>> It is not explicitly mentioned in the spec, but I guess I
>> can safely assume, that the data source denoted by
>> jta-data-source is of type "javax.sql.XADataSource"?
>>
>> After the JPA implementation has obtained an XAConnection
>> from this XADataSource, is it expected to
>> to do any calls (and if so, in any specific order) on this
>> XAConnection?
>>
>> E.g. is it necessary, to call XAConnection.getConnection()
>> to trigger that the app server calls XAConnection.getXAResource()
>> on the very same XAConnection? Or is it sufficient to just
>> call "XADataSource.getXAConnection()" to trigger this?
>>
>> (Some background: we don't use JDBC connections (being not
>> an ORM) and probably we would need to provide our own
>> XADataSource implementation, so that the app server picks up
>> our own XAResource implementation)
>>
>> Thank you!
>>
>> 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* <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
>> proprietary information. Any unauthorized review, use,
>> disclosure or
>> distribution is prohibited. If you are not the intended
>> recipient,
>> immediately contact the sender by reply e-mail and destroy
>> all copies of
>> the original message.
>>
>>
>>
>>
>>
>> -- *
>> 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* <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
>> proprietary information. Any unauthorized review, use, disclosure
>> or
>> distribution is prohibited. If you are not the intended recipient,
>> immediately contact the sender by reply e-mail and destroy all
>> copies of
>> the original message.
>>
>>
>>
>>
>>
>>
>> -- *
>> Christian Romberg
>> Chief Engineer* | Versant GmbH
>> (T) +49 40 60990-0
>> (F) +49 40 60990-113
>> (E) *cromberg_at_versant.com* <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
>> proprietary information. Any unauthorized review, use, disclosure or
>> distribution is prohibited. If you are not the intended recipient,
>> immediately contact the sender by reply e-mail and destroy all copies of
>> the original message.
>>
>>
>>
>>
>
>
> --
> 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
> proprietary information. Any unauthorized review, use, disclosure or
> distribution is prohibited. If you are not the intended recipient,
> immediately contact the sender by reply e-mail and destroy all copies of
> the original message.
>
>
>
>
--
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
proprietary information. Any unauthorized review, use, disclosure or
distribution is prohibited. If you are not the intended recipient,
immediately contact the sender by reply e-mail and destroy all copies of
the original message.