One comment inline ...
From: Jacques Durand
[mailto:]
Sent: Monday, Jul 18, 2005 18:15
PM
To:
Subject: [ws-rx] A
rewording of "Sequence termination on Fault" issue
Title: Sequence
termination on Fault
Description: The
RM Destination imperatively terminates a sequence due to one of these
unrecoverable errors:
- wsrm:SequenceTerminated
-
wsrm:MessageNumberRollover
-
wsrm:LastMessageNumberExceeded
Then any pending non-acknowledged message will be lost
for the sequence.
<Sanjay> In addition, I am not sure about the
fate of acknowledged messages when a sequence is abruptly terminated. Consider
the case where the contract between the Destination RM and the Destination
Application is In-Order delivery, and also consider that there are some
holes in the sequence at the time of sequence termination due to a
MessageNumbeRollover fault. In this case, it is not clear how the
Destination RM is supposed to handle the acknowledged messages in the
incomplete sequence. If you agree, you may want to change the last
sentence above to something on the lines of - "The semantics of sequence
termination due to a fault occurrence are not clearly
specified".</Sanjay>
Justification:
Unless an accurate and final acknowledgement status was sent back at the time
the sequence is closed, the Source will not know if some non-acknowledged
messages were actually received before the termination occurs. This gives the
source two unpleasant options: (a) resend all non-acknowledged message in a
new sequence, with the risk of causing undetectable duplicates, (b) not resend
any, and these will be lost.
Target:
core
Type:
design
Proposal: Two
options need be discussed: Option (1): At the time a Destination-controlled
termination gets into effect, a final and accurate Acknowledgement for the
entire sequence is sent back. Option (2): After the fault was notified to
Source, simply rely on regular termination procedure (either expiration-based,
or under Source control, so that the Source can complete its resending of
pending messages and get the final acks), meanwhile reject any message for
this sequence that exceeds the ending number in case of MessageNumberRollover
or LastMessageNumberExceeded.
