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Subject: Re: [ws-rx] Minimalist GetMessage proposal


Matt

Thanks for the detailed feedback. Excellent points.
> I don't think that this proposal is complete without some discussion 
> of outbound/offered Sequence lifetimes. I guess it is always OK to 
> Terminate/Close the outbound sequence without affecting the offered 
> one - and doing this allows the inbound messages to keep flowing until 
> the client has all its replies. 
Yes I agree.
> However, if the offered sequence is Terminated/Closed before the 
> outbound one then I'm not sure what the service should do - if it 
> knows there should be a reliable reply should it fault the message on 
> arrival at the RMD, or should it allow it to be processed and discard 
> the reply message(s)?
If the case is req-reply and the reply is ready, then it could be 
returned on the backchannel (like the first echorequest in my example). 
If the response is delayed or there is more than one response then it 
seems to me these should just be thrown away. After all the reliability 
guarantee is now over (as the sequence is closed). If RM was not present 
these would be thrown away, so that seems logical.
>
> On a similar vein, it is always possible for the client to send 
> Close/Terminate for the outbound sequence to the server (after all, it 
> can address the server), but the Server cannot send Close/Terminate 
> messages to the client. In the case where the server _must_ 
> Close/Terminate the offered sequence, how should it inform the client? 
> By faulting the next outbound message with a Sequence 
> Closed/Terminated fault for the offered sequence?
That is possible. The other option is that we add a way of 
closing/terminating an offered sequence that is initiated by the client.
> How is the 2-way CloseSequence/CloseSequenceResponse interaction 
> supposed to happen for the offered sequence? Does the CloseSequence 
> flow on a getMessage HTTP response flow, and the Response go out on a 
> new HTTP flow from the client? 
Thats what I showed in the second diagram in the example flow. I think 
that is a reasonable approach.
> (The same question applies to the other 2 way interactions.) Also, is 
> the getMessage HTTP response flow allowed to contain a Sequence fault?
Yes I don't see any reason not to.
> Of course, if you link the two sequences then there is less need to 
> handle some of the above.... but that would have to be explained instead.
I agree that would solve these, but I would rather not link the 
sequences if we can solve these issues without that.

Regards,
Paul
> Paul Fremantle <paul@wso2.com> wrote on 03/05/2006 20:05:26:
>
> > Based on some of the discussions it seemed to me that it could be
> > valuable to produce a completely "minimalist" GetMessage proposal.
> >
> > This is a new proposal that is based on the previous WSO2 proposal.
> >
> > The proposal removes the MessageID selector in the GetMessage - relying
> > on simply getting whatever message the server sends back next.
> >
> > Also it removes the section 4.2. Effectively section 4.2 is an
> > optimisation: for example to support unreliable-in/reliable-out a 
> client
> > could do a createsequence+offer and never use the outgoing sequence. In
> > this case there is an overhead, which 4.2 aimed to remove, but this
> > simplifies the proposal by focussing on the bare minimum required to
> > support the most common use cases, but still allowing the other use 
> case
> > with a slight overhead.
> >
> > I've also included a sample message flow which I hope helps understand
> > the proposal and show the general usage.
> >
> > Paul
> >
> > --
> >
> > Paul Fremantle
> > VP/Technology, WSO2 and OASIS WS-RX TC Co-chair
> >
> > http://feeds.feedburner.com/bloglines/pzf
> > paul@wso2.com
> >
> > "Oxygenating the Web Service Platform", www.wso2.com
> >

-- 

Paul Fremantle
VP/Technology, WSO2 and OASIS WS-RX TC Co-chair

http://feeds.feedburner.com/bloglines/pzf
paul@wso2.com

"Oxygenating the Web Service Platform", www.wso2.com



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