RE: Issue 6472 Proposal - WS-Eventing EventSourceUnableToProcess: Distinguish temporary v permanent failure

Katy,
Suggestion one looks like it might work the best, but the text should be explicit that there is no guarantee that the operation will work after that period.  Perhaps some wording like:

/wse:RetryAfter
  This element (whose content is of type xs:unsignedLong) is a suggested minimum duration in milliseconds to wait before retransmitting the message. This element is a hint only, and there is no guarantee that the operation will succeed if retried after the specified duration. Omission of this element indicates that a retry is never likely to succeed.

-Geoff

From: public-ws-resource-access-request@w3.org [mailto:public-ws-resource-access-request@w3.org] On Behalf Of Katy Warr
Sent: Friday, January 30, 2009 4:25 AM
To: public-ws-resource-access@w3.org
Subject: Issue 6472 Proposal - WS-Eventing EventSourceUnableToProcess: Distinguish temporary v permanent failure


Here are a couple of proposed solutions for http://www.w3.org/Bugs/Public/show_bug.cgi?id=6472.

I've added the text changes that I think would be required for both proposals as concern was raised on the last call regarding the amount of change required for this issue.

thanks
Katy

Suggestion 1: Introduction of "retryAfter"
------------------------------------------

Introduce an optional retryAfter element  (in homage to ws-addressing soap ;o) ) in the detail of EventSourceUnableToProcess and UnableToRenew.  Absence of the retryAfter element would mean: don't bother to retry.

This suggestion has the advantage that it reuses an existing pattern from another spec.  It also is more useful to the client as it gives some indication as to when it might be worth retrying.  This may be useful (for example) if an event source had too many subscribers and was therefore being taken off-line for a while.

Here's an example fault using this suggestion:

 <S:Fault>
   <S:Code>
     <S:Value>
        S:Sender
     </S:Value>
     <S:Subcode>
        <S:Value>wse:EventSourceUnableToProcess</S:Value>
     </S:Subcode>
   </S:Code>
   <S:Reason>
     <S:Text xml:lang="en">The event source has too many subscribers</S:Text>
   </S:Reason>
   <S:Detail>
     <wse:RetryAfter>1000</wse:RetryAfter>
   </S:Detail>
 </S:Fault>


Required Changes to the specification:

1) Add to Section 5:Faults

Fault detail elements:

The following element is used to convey additional information in the faults.
Retry After
  The following describes the <wse:RetryAfter> element:
  /wse:RetryAfter
  This element (whose content is of type xs:unsignedLong) is a suggested minimum duration in milliseconds to wait before retransmitting the message. Omission of this element indicates that a retry is never likely to succeed.
  /wse:RetryAfter/@{any}
  Optional extensibility attributes that do not affect processing.

2) Add "<wsa:RetryAfter> Optional" to the [Detail] section of 5.6 EventSourceUnableToProcess and 5.7 UnableToRenew


Suggestion 2: PermanentFailure Subsubcode
-----------------------------------------

A simpler, but less powerful solution, would be to enable an event source to set a subsubcode in the fault to indicate that the error was permanent.  Absence of this subsubcode would indicate to clients that it may be worth retrying the request.

Here's an example fault using this suggestion:

  <S:Fault>
   <S:Code>
     <S:Value>
        S:Sender
     </S:Value>
     <S:Subcode>
        <S:Value>wse:EventSourceUnableToProcess</S:Value>
        <S:Subcode>wse:PermanentFailure</S:Subcode>
     </S:Subcode>
   </S:Code>
   <S:Reason>
     <S:Text xml:lang="en">The endpoint is no longer acting as an event source</S:Text>
   </S:Reason>

  </S:Fault>

Required Changes to the specification:

1) Section 5 Faults.
In the table following "The definitions of faults use the following properties:"
change the text in the subcode row from
"The fault subcode"
to
"The fault subcode (with optional nested subcode)".

2)Change [subcode] row of section of 5.6 EventSourceUnableToProcess and 5.7 UnableToRenew to:

wse:EventSourceUnableToProcess
The EventSourceUnableToProcess subcode can be further narrowed in scope by use of an optional nested subcode <wse:PermanentFailure>. Inclusion of this nested subcode indicates that a retry is never likely to succeed.


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