Re: [ws-tx] Issue 007 - WS-C: Make Register/RegisterResponse retriable

[Ian Robinson <ian_robinson@uk.ibm.com>]

Regarding WS-RM, the "scope of work" section of the charter states:

"As general principles, these protocols ... must not depend on the
availability of reliable message delivery mechanisms outside of these
specifications."



This issue proposes a change to the semantic of the Register request but I
believe that none is needed. Retrying a Register request because of network
failures is not the only scenario in which a Participant can be registered
multiple times for the same transaction. The important consideration is
whether or not the multiple participant instances will behave properly when
they are directed to complete according to the specific agreement protocol
(e.g. AT or BA). And the state tables ensure that they can.



If the TC believes clarification is required then I would suggest the
following text:

A Coordinator is not required to detect duplicate Register messages, but
MAY attempt to do so by means that are out of the scope of this
specifiction. A registration requester MAY send multiple Register messages
to a Coordinator that does not detect duplicates - for example because it
retried a Register request following a lost RegisterResponse. If a
registration requester registers multiple times for the same activity then
the registered Participants MUST be prepared to handle multiple protocol
messages from a Coordinator that treats the multiple Register requests as
distinct Participants. There are a number of simple strategies for
accomplishing this. For example, the registration requester can generate a
unique ReferenceParameter for each Participant EPR that is passed in a
Register request.


Regards,
Ian Robinson
STSM, WebSphere Messaging and Transactions Architect
IBM Hursley Lab, UK
ian_robinson@uk.ibm.com


                                                                           
             Alastair Green                                                
             <alastair.green@c                                             
             horeology.com>                                             To 
                                       Doug Davis <dug@us.ibm.com>         
             13/12/2005 17:19                                           cc 
                                       ws-tx@lists.oasis-open.org          
                                                                   Subject 
                                       Re: [ws-tx] Issue 007 - WS-C: Make  
                                       Register/RegisterResponse retriable 
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




+1.

Either we do it at the coord protocol level, or we start to mandate
something like WS-RM, which I would not favour, and would create some
pretty major ripple effects in specs and implementations.

Alastair

Doug Davis wrote:

      And what is that transport mechanism?  By default neither WSA nor
      SOAP will do
      retries.
      -Doug


                                                                           
 Kevin Conner                                                              
 <Kevin.Conner@jboss.co                                                    
 m>                                                                        
                                                                        To 
                                     Doug Davis/Raleigh/IBM@IBMUS          
 12/13/2005 04:31 AM                                                    cc 
                                     Christopher B                         
                                     Ferris/Waltham/IBM@IBMUS, Mark Little 
                                     <mark.little@arjuna.com>,             
                                     ws-tx@lists.oasis-open.org            
                                                                   Subject 
                                     Re: [ws-tx] Issue 007 - WS-C: Make    
                                     Register/RegisterResponse retriable   
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           





      Doug Davis wrote:
      > One thing that concerns me about using the wsa:MessagID is the
      assumption
      > that you'll use the same messageID on each retry.  Can the Tx spec
      really
      > require this?  Other specs (like WSA) which are infrastructural can

      > probably make
      > this kind of requirement (if they need to), but I always viewed Tx
      as
      > sitting on top
      > of these infrastructural layers and not so much as being part of
      them.
      > Implementations
      > will vary on this view but I wouldn't think Tx would want to
      mandate this
      > kind of choice.
      > thanks,
      > -Doug

      This really came out of the description of the original problem.  A
      request/response conversations was initiated and the initiator
      crashed
      before receiving the response.  The replay of a message at this
      level,
      especially as we are using WS-Addressing, would surely become the
      domain
      of a reliable transport.  My suggestion was therefore to defer this
      to
      the transport mechanism to replay the conversations and not the
      higher
      level protocols.

                      Kev