RE: [wsbpel] Re: completionHandler example

["Chris Keller" <chris.keller@active-endpoints.com>]

Satish,

No, I don't mean we add a complete activity that gets called in the event
handler, not sure how you read that in what I said.  My thinking is instead
of adding new top level handlers to scopes we add new event types, which can
be listened for in the scope/eventHandlers container.

In terms of completion handling my thinking was that scope completion always
happens when no fault is thrown.  In the new case it is triggered explicitly
by the addition of your new activity <complete/>.  Whether or not someone
cares about the actual event which is generated by the completion is a
different story.  That is what is addressed by your completionHandler and my
proposal to have completion be an event.

Named completion could be accomplished by the addition of a message or name
attribute attribute to the complete activity you have suggested such as
<completion message="..."/>.   Then we use the either use the matching
mechanism of the message and event handler for the named type of event (i.e.
completion in this case), since <onEvent> already includes an attribute to
receive a message.  Or we add a new kind of matching for named events of a
type (e.g., <onEvent type="completion" name="myname"/>).

- Chris

-----Original Message-----
From: Satish Thatte [mailto:satisht@microsoft.com] 
Sent: Tuesday, October 05, 2004 2:16 PM
To: Chris Keller
Cc: wsbpeltc; ygoland@bea.com
Subject: RE: [wsbpel] Re: completionHandler example

But how would the event handler force completion?  Do you mean we add a
complete activity that gets called in the event handler but only
completes the scope the handler is attached to?  IOW no completion
handler and no named completion?

-----Original Message-----
From: Chris Keller [mailto:chris.keller@active-endpoints.com] 
Sent: Tuesday, October 05, 2004 7:14 AM
To: Satish Thatte
Cc: 'wsbpeltc'; ygoland@bea.com
Subject: RE: [wsbpel] Re: completionHandler example

Satish,

I am also unsure of the point of failure to which you are eluding, but
in
general support some of the concepts you are proposing.  I would suggest
a
change to your recent proposed additions, completion and termination
handlers, to make it easier to add potentially more in the future (e.g.,
finally and user-defined events), without the introduction of new
elements.
I suggest that we change the onEvent mechanism to deal more generically
with
event types.  The additions you have proposed are essentially events
generated by scopes.  So the idea would be to allow onEvent to include a
type.  For example:

 <eventHandlers>
	<onEvent type="completion" ...> ... </onEvent>
 </eventHandlers>

The default type could be "message" (or "receive", pick a good name),
which
is the current usage of onEvent.

Thoughts?

- Chris

-----Original Message-----
From: Yaron Y. Goland [mailto:ygoland@bea.com] 
Sent: Monday, October 04, 2004 8:05 PM
To: Satish Thatte
Cc: wsbpeltc
Subject: [wsbpel] Re: completionHandler example

But Satish, that is exactly what my example does. Could you please be 
more specific in identifying the point of failure?
	Thanks,
		Yaron

Satish Thatte wrote:
> 
> 
> That doesn't work if you want to do cascading completions aka named
> completions.
> 
> -----Original Message-----
> From: Yaron Y. Goland [mailto:ygoland@bea.com]
> Sent: Thursday, September 30, 2004 11:17 AM
> To: Satish Thatte
> Cc: wsbpeltc
> Subject: Re: completionHandler example
> 
> I realize why putting the completion handler logic before the complete
> doesn't work but why doesn't putting it after the completion handler
> work?
> 
> scope
>     variables
>        variable name="MessageTrackerVariable"...
>     sequence
>        scope wrapper
>           flow
>              scope A_end_in_complete_to_wrapper
>                 ...
>              scope B_end_in_complete_to_wrapper
>                 ...
>              scope C_end_in_complete_to_wrapper
>                 ...
>        scope CompletionHandler
>           (Check MessageTrackerVariable and see if any cleanup is
> needed)
> 
> Because the exit point of a completed scope is always well defined
can't
> 
> the completion handler logic be placed after the completed scope?
> 
>         Yaron
> 
> 
> Satish Thatte wrote:
>  >
>  >
>  > Yaron,
>  > 
>  > During the F2F you asked for a completionHandler example.  Here is
my
>  > try with some explanations.  Please let me know if this makes sense
to
> you.
>  >
>  > 
>  > Satish
>  > 
>  >
>  > The completionHandler is the common process logic required at all
> points
>  > of premature completion within a scope.  The only difference
between
>  > copying it just before each occurrence of a <complete/> activity
thus
>  >
>  > 
>  >
>  > <sequence>
>  >
>  >     <completionHandler logic>
>  >
>  >     <complete/>
>  >
>  > </sequence>
>  >
>  > 
>  >
>  > and the proposed completionHandler feature is that the
> completionHandler
>  > logic executes *after* termination of all activities in the
> prematurely
>  > completed scope.  Thus it is a pure macro if the prematurely
completed
> 
>  > scope does not contain concurrent activities.  Many examples of the
> use
>  > of premature completion, e.g., completion of N out of M activities
in
> a
>  > flow, do involve concurrency.  Consider a case where M suppliers
had
>  > been contacted concurrently and the process was waiting for
> asynchronous
>  > responses (forgive the use of the word :-)) from them.  After at
least
> N
>  > of them send responses the scope completes.  Suppose the
conversation
>  > with each supplier is wrapped in a scope and a terminationHandler
is
>  > used to inform a supplier whose conversation was forcibly
terminated
>  > that their response is not needed.  But perhaps we did not or could
> not
>  > ensure that *exactly* N replies arrive because the race was too
tricky
> 
>  > to control.  Thus it is possible that more than N responses
arrived. 
>  > The completion handler could detect this situation, pick the N we
> really
>  > want and inform the rest that their responses have been rejected so
> that
>  > we exit the scope cleanly with exactly N accepted responses.
>  >
> 

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