Re: BUG #5297: Add XATMI C API

Michael Musgrove <mmusgrov@redhat.com> writes:

The response to this issue says it is "Not a bug". Would it be possible
for someone to provide an indication of how much effort is involved in
providing XA support in the C API library (libpq)?

What do you consider to be "providing XA support"? XA requires there to
be a transaction manager somewhere, which is not something libpq can
provide since it's dependent on the good graces of its host application.
Maybe there would be some value in teaching libpq to interact with an
external XA manager, but what exactly do you think is required?

regards, tom lane

On 04/21/2011 05:43 PM, Tom Lane wrote:

Michael Musgrove<mmusgrov@redhat.com> writes:

The response to this issue says it is "Not a bug". Would it be possible
for someone to provide an indication of how much effort is involved in
providing XA support in the C API library (libpq)?

What do you consider to be "providing XA support"? XA requires there to
be a transaction manager somewhere, which is not something libpq can
provide since it's dependent on the good graces of its host application.
Maybe there would be some value in teaching libpq to interact with an
external XA manager, but what exactly do you think is required?

regards, tom lane

I am referring to the X/Open specification Distributed Transaction
Processing: The XA Specification
(pubs.opengroup.org/onlinepubs/009680699/toc.pdf). If postgresql
provides a conforming Resource Manager switch then we can include
postgresql work along with interactions with other Resource Managers
(Oracle, DB2) in the same transaction. For example the equivalent
support in Oracle that I am asking for is documented at
http://download.oracle.com/docs/cd/B10501_01/appdev.920/a96590/adga1_xa.htm

Thanks,
Mike

On 21.04.2011 20:04, Michael Musgrove wrote:

I am referring to the X/Open specification Distributed Transaction
Processing: The XA Specification
(pubs.opengroup.org/onlinepubs/009680699/toc.pdf). If postgresql
provides a conforming Resource Manager switch then we can include
postgresql work along with interactions with other Resource Managers
(Oracle, DB2) in the same transaction. For example the equivalent
support in Oracle that I am asking for is documented at
http://download.oracle.com/docs/cd/B10501_01/appdev.920/a96590/adga1_xa.htm

When I wrote the patch for the backend support, I was not able to find
any open source implementations of X/Open XA-compatible resource
managers or transaction managers, which makes it kind of hard to
implement the API correctly. There was plenty of JDBC XA
implementations, however, so I used that for testing.

If you can find something to test it with, it probably wouldn't be that
hard to write the library.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

We would certainly be very interested in testing XA support. Our project
is called BlackTie - it's an XATMI implementation. We use the JBossTS
transaction manager for the transaction engine - although JBossTS is
written in Java, providing XA support was reasonably easy since it
conforms to the OTS specification which means we can control
transactions from a C based XA environment.

There is an example of using different resource managers within
transactions:
https://svn.jboss.org/repos/blacktie/trunk/atmibroker-xatmi/src/example/txfooapp
The files ora.c and db2.c show user code accessing resources from two
different vendors - the XA specific information is defined in
btconfig.xml (basically it just exposes the XA open string, the symbol
name of the xa switch structure and the name of the library that exports
the switch symbol).

Sorry, the link I included was for committers. Try this instead
https://anonsvn.jboss.org/repos/blacktie/trunk/atmibroker-xatmi/src/example/txfooapp/
and the project page is http://www.jboss.org/blacktie