Re: [provision] Async execution (was"Re: [provision] Asynchronou s requests").

[Gary P Cole <Gary.P.Cole@sun.com>]

Thank you, Jeff.  I agree that the client's effort to check the response 
(and see that it is complete rather than pending) is not very large.  I 
also understand that certain providers will not support asynchronous 
operations at all.

Since the requestor has a way to specify that either type of execution 
is okay (that is, by omitting the execution attribute of the request) 
and since this is implicitly the default, shouldn't a provider that will 
not support asynchronous operations fail any request that specifies 
execution="asynchronous"? (We can have it return result="failed" and 
error="unsupportedExecutionType" to make this clear.)

gpc

Jeff Bohren wrote:

>Gary,
> 
>If the provider is not a provisioning system, but rather is a SPML front end to a resource (such and a directory, an RDBMS, etc), then it will likely not support asynchronous operations at all. In such a case the choice would be to execute everything synchronously or fail every asynchronous request. 
> 
>No developer is going to add asynchronous message handling code to a provider for a system to which they can execute all requests synchronously. It's not going to be done because it adds no additional real functionality.
> 
>It seems to me that to have a client look at the results of the request and detect that an asynchronous request was performed synchronously is not a lot of extra work. After all, the client must look at the response anyway to know that the request was successfully submitted. To have one extra bit of logic to see the the request was actually fulfilled seems to be worth the benefit.
> 
>Jeff Bohren
>
>	-----Original Message----- 
>	From: Gary P Cole [mailto:Gary.P.Cole@Sun.COM] 
>	Sent: Mon 10/25/2004 12:57 PM 
>	To: Cohen, Doron; Jeff Bohren; Jeff Larson 
>	Cc: PSTC 
>	Subject: Re: [provision] Async execution (was "Re: [provision] Asynchronou s requests").
>	
>	
>
>	Doron,  yes, this does help.  I think we agree, although I must confess
>	that I am still unsatisfied.  I think that I would prefer to say that if
>	a requestor specifies execution="asynchronous" that a provider must
>	either execute the requested operation asynchronously (or must fail the
>	request).
>	
>	Jeff Bohren and Jeff Larson,  why it is so important that a provider
>	must be able to execute synchronously an operation that was requested to
>	execute asynchronously?  (I understand that it may be a little bit
>	unnecessarily expensive, but is there a deeper reason?)
>	
>	gary
>	
>	Cohen, Doron wrote:
>	
>	>Gary,
>	>
>	>I think we are close and I agree to the way you put it, however, with the
>	>risk I am repeating myself, I would like to stress that I do not really
>	>object to the optimization involved in changing a async request to sync. I
>	>am concerned with the way one would design an RA client app. If I have a
>	>client that issue async operations to PSP and use separate thread to check
>	>for the results, then the fact that the PSP does the optimization and return
>	>the results to the requesting thread is of little help to me. In fact, it
>	>may well introduce to me more burden of enhancing the client code to handle
>	>that situation.
>	>
>	>Now, I agree that for the sake of satisfying the optimization requirement,
>	>we would need to enables the RA to specify to the PSP, "handle the request
>	>async, but in case you can do it quickly, do a sync". If we choose to go
>	>this way we need to provide a clear definition on how the implementation is
>	>supposed to achieve this. For me it is sufficient that we state it in a
>	>clear manner either by adding a new mode or by explicit description in the
>	>normative text for the case no mode is specified.
>	>
>	>Does this help?
>	>
>	>Doron
>	>
>	>-----Original Message-----
>	>From: Gary P Cole [mailto:Gary.P.Cole@Sun.COM]
>	>Sent: Monday, October 25, 2004 6:24 PM
>	>To: Cohen, Doron
>	>Cc: PSTC
>	>Subject: Re: [provision] Async execution (was "Re: [provision] Asynchronou s
>	>requests").
>	>
>	>Doron,
>	>
>	>I'm not sure that you're in the minority.  I agree with you that
>	>honoring a request for explicit execution mode (or failing the request)
>	>is more straightforward.  The notion that a client can simply omit the
>	>'execution' attribute (in order to indicate that the client will accept
>	>either mode) makes this argument even more compelling.
>	>
>	>However, it seems to me that Jeff Bohren's point is also very good:
>	>    If a service processes an asynchronous request synchronously,
>	>    there is no reason to return an asynchronous response.
>	>    The service knows the request was processed synchronously,
>	>    and it should be reported as such.
>	>
>	>Executing an operation synchronously (whenever a provider knows that it
>	>can do this) seems to be a reasonable optimization.  It does seems a
>	>little silly to make a provider 1) generate and return a requestID and
>	>2) hold onto results waiting to be asked for status.
>	>
>	>I suppose that I could live with a little bit of silliness (since the
>	>provider always has the option of failing the request if it is
>	>absolutely unwilling to execute asynchronously an operation that the
>	>provider could execute synchronously), but it would be nice to have a
>	>better answer to Jeff Bohren's point.
>	>
>	>If a request for asynchronous execution will always receive a
>	>synchronous response
>	>(that contains the requestID), and
>	>if a provider can execute the requested operation synchronously, then
>	>why not let the provider return the results of the completed operation
>	>(rather than a requestID)?
>	>
>	>gary
>	>
>	>Cohen, Doron wrote:
>	>
>	> 
>	>
>	>>1) I may be in a minority here, but I still feel differently about this
>	>>point. To me ,honoring the client request with regard to the mode of the
>	>>operation is key. Allowing the PSP to behave differently than requested
>	>>means more complexity on the RA side since the RA must be able to handle
>	>>both scenarios instead of maintaining a simplicity of acting in one manner.
>	>>Also, the RA has no way to predict the time that the request would execute
>	>>   
>	>>
>	>,
>	> 
>	>
>	>>and I must admit that in most cases, even the PSP would not really know
>	>>that.
>	>>Overall, I find a design that honors the RA request more straight forward
>	>>and recommend that if we choose to allow the PSP to convert the execution
>	>>mode, let the RA say so by providing an additional indication that he is
>	>>capable of handling PSP change of mode.
>	>>
>	>>
>	>>   
>	>>
>	>
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>	>
>	> 
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