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Subject: Re: [wsrm] Discussion on Duplicate elimination issue from 6/14 minutes

I propose to allow both 1) and 3) behaviours , that is:

1) Sending rmp allowed to return buffered response from previous 
invocation with rm-acknolwedgement indication, or

3) define a new RM-Fault called "Response Payload Not Available for 
Duplicate request" which gets sent with
a soap fault in the case where the duplicate invoke requires  a response 
which is not available because of duplicate request elimination.

Tom Rutt

Sunil Kunisetty wrote:

> Tom Rutt wrote:
>> I have one question inserted below.
>> Tom Rutt
>> Sunil Kunisetty wrote:
>>> Here is the mail I sent on Duplicate Elimination a week ago.
>>> It has the summary, possible solutions and my preferred solution.
>>> ----------------------------------------------------------------------------------------------------- 
>>> I'd like to summarize the options of using Duplicate Elimination for a
>>> Request-Response MEP.
>>> 1) Cache the message until the original request expires and Send the
>>>    "payload  response" for every subsequent request.
>>> 2)  Send an empty SOAP envelope.
>>>      (Note that when there is no AckRequested, there won't be any 
>>> Ack and
>>>      hence the SOAP envelope will have empty Header/body).
>>> 3)  Send a signal that it is a "Duplicate Message".
>>> 4)  Spec. says that this is combination is not supported.
>>> While I personally like (4),  we can't do it as the TC voted to support
>>> this combination.
>>> I'm very un-comfortable with (2) as it will cause all kinds of 
>>> issues and
>>> as such it is meaningless/un-informative to send "empty signal".
>>> As per (1), while it is theoritcally reasonable and easy to implement,
>>> it is impractical from a product/solution perspective.
>>> Here are few reasons:
>>> (i) Potentially can throttle the server with memory being sucked up.
>>>    Generally speaking, expire time is used optimistically and will 
>>> have a
>>>    large life span. Caching responses that long is not too good .
>>> (ii) I believe this thing (async. responses) is beyond the scope
>>>    of this specification and should be handled  in the "OASIS 
>>> Asynchronous
>>>    Service Access  Protocol TC"  [1]
>>> (iii) There are many subtle things about caching responses:
>>>         - there should be mechanism to invalidate the cache
>>>         - what if the request has time sensitive information. for ex.,
>>>           if I ask for getStockQuote for Oracle with a duration of 
>>> say 1 hr...
>>>           Assume the first  message is lost.
>>>           Say the RMP resent the same message after 10 mins... they may
>>>           get a stock quote that was 10 mins. ago.
>>>           So if time sensitive data exists, there should be mechanism
>>>           for data resync..
>>> So for these reasons, I just like a RM signal [3] solution so that
>>> the application can resend the request.
>> The situation that causes the most trouble is when the response had 
>> been previously sent, so the responder RMP
>> has no response payload to return since it did not invoke the second 
>> deliver. Thus the sender resending will
>> not help all all.
>> The reason to give an indication is so the sender will not continue 
>> to resend the duplicate, in cases where the original
> Right. That's why I said I like to send a RM signal so that the Sender 
> can either resend the Message
> with a different MessageId or query as you suggested.
> Option 2 (sending an empty SOAP envelope) is the wrong thing to do.
>> response is lost. However an indication will let the sender know it 
>> SHOULD NOT resend the duplicate. Instead, it
>> could invoke other operations to query the server state (eg, get the 
>> current ballance of the account to see if the
>> first invoke actually happened.

Tom Rutt	email: tom@coastin.com; trutt@us.fujitsu.com
Tel: +1 732 801 5744          Fax: +1 732 774 5133

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