Re: [wsbpel] Issue 190 - BPEL Internal Faults (New Proposed IssueAnnouncement)

[Francisco Curbera <curbera@us.ibm.com>]

I guess one of the points of the immediate termination condition is that
termination is essentially always invisible to partners of the process. The
net effect of this change (and from my perspective the actual aim of this
proposal) would be to allow engines the flexibility to deciding how to deal
with these situations, termination being an option. Any form of standard
fault semantics limit that flexibility because the engine would be forced
to follow the usual scope termination/fault propagation behavior with
likely the result of discarding many recoverable process instances - and
posisble days or months of process work.

Paco



                                                                       
                      Prasad Yendluri                                  
                      <pyendluri@webmet        To:       Francisco Curbera/Watson/IBM@IBMUS
                      hods.com>                cc:       Danny van der Rijn <dannyv@tibco.com>, wsbpel@lists.oasis-open.org
                                               Subject:  Re: [wsbpel] Issue 190 - BPEL Internal Faults (New Proposed Issue
                      02/04/2005 02:30          Announcement)          
                      PM                                               
                                                                       




Hi,

1. Isn't this the same issue as the one raised by issue 187 where we ask if
there are any constraints in handling of the standard faults? This is
proposing a specific resolution where it is recommended that the process
always terminates immediately.

2.  I tend to side with Danny on this. I don't think we should require that
the process terminates immediately always. IMO in at least certain cases
this may not be a fatal situation for the whole process (it could be
confined to the scope) and other parts of the process may be able to
continue by compensating for pertinent. Perhaps the impact could limited to
the immediately confining scope and the process could continue, perhaps the
area the fault occurred could be non-fatal to whole process (e.g. related
look-up rather than modification of any information) or caused by some
transient condition that could go away on a retry etc. I think the process
(fault handler) should be given a chance to handle the situation rather
than terminate always.

3. If we do end-up going the "terminate" always way, we must minimally
*not* preclude logging the condition, which could be more intelligent if
the faults could be attached some "fault data" (ref issues 187 and 185).

Regards, Prasad

-------- Original Message --------
                                                                       
 Subject Re: [wsbpel] Issue 190 - BPEL Internal Faults (New Proposed Issue
       : Announcement                                                  
                                                                       
   Date: Fri, 4 Feb 2005 13:23:17 -0500                                
                                                                       
   From: Francisco Curbera <curbera@us.ibm.com>                        
                                                                       
     To: Danny van der Rijn <dannyv@tibco.com>                         
                                                                       
     CC: wsbpel@lists.oasis-open.org                                   
                                                                       


Hi Danny,

BPEL so far does not support any technique for modularizing process
authoring, so the situation you describe is a bit out of scope right now.
In any case, my view is that the idea that authors of business process are
going to be adding code to deal with things like unsupportedReference is
just not realistic. I would even argue that those faults don't actually
belong at the BP modeling level and need to be dealt with in a different
way.

Dieter's suggestion allows implementations to manage these situations in
the best possible way.  This is specially important in the case of long
running processes, where months or years of work can be thrown out the
window when one of these faults is encountered (the current semantics
require the complete unwinding of the execution stack if the fault is not
caught and a generic catch all is essentially good for nothing). Typically
you want to allow manual intervention to figure out whether the process can
be repaired, terminated if not.

Paco




>From: Danny van der Rijn
>To:       wsbpel@lists.oasis-open.org

>cc:

>Subject:  Re: [wsbpel] Issue 190 - BPEL Internal Faults (New Proposed
Issue Announcement
        02/03/2005 01:47 PM


[Resending this with appropriate header to save Tony/Peter the trouble]

-1

As I pointed out in our last face to face, this kind of approach will make
any kind of modularization extremely difficult.  It will give no way for a
developer of a piece of BPEL code to protect against the "modelling error"
(legacy term: "programming error") of another modeller whose attempt to
model the real world failed in a tangible instance.

Danny

Tony Fletcher wrote:
      This issue has been added to the wsbpel issue list with a status of
      "received". The status will be changed to "open" if the TC accepts it
      as identifying a bug in the spec or decides it should be accepted
      specially. Otherwise it will be closed without further consideration
      (but will be marked as "Revisitable")


      The issues list is posted as a Technical Committee document to the
      OASIS WSBPEL TC pages on a regular basis. The current edition, as a
      TC document, is the most recent version of the document entitled in
      the "Issues" folder of the WSBPEL TC document list - the next posting
      as a TC document will include this issue. The list editor's working
      copy, which will normally include an issue when it is announced, is
      available at this constant URL.


      Issue 190: BPEL Internal Faults
      Status: received
      Date added: 3 Feb 2005
      Categories: Fault handling
      Date submitted: 3 February 2005
      Submitter: Dieter Koenig1
      Document: WS-BPEL Working Draft, December, 2004
      Related Issues: Issue 163 : languageExecutionFault, Issue 169 :
      Transition condition error handling clarification, and Issue 187 :
      Legality of Explicitly throwing or rethrowing Standard faults.
      Description:
      There are a number of cases in the current spec where the behavior of
      a process is described as *undefined*, in particular, after
      recognizing internal errors described as standard faults.


      With the exception of "bpel:joinFailure", *all* of these situations
      represent modelling errors that cannot be dealt with by the business
      process itself in a meaningful way. This behavior becomes even more
      questionable for catchAll handlers that try to deal with multiple
      application faults and unexpectedly encounter a standard fault.


      Submitter's proposal: Instead of allowing processes to catch these as
      standard faults, we propose that the process instance must
      *terminate* immediately when such a situation is encountered.


      The behavior of terminate is well-defined in BPEL -- as far as BPEL
      is concerned the instance execution ends when terminate is
      encountered without any fault handling behavior. Any additional
      facilities for extended support for, e.g., repair and continue, is
      definitely out of scope.


      This approach would also create a clear direction for dealing with
      any pathological situation within an inlined language (Issue 163) and
      therefore also for errors within transition conditions (Issue 169).


      Changes: 3 Feb 2005 - new issue


      Best Regards,
      Tony