Re: [ws-rx] MessagePending

[Doug Davis <dug@us.ibm.com>]

Would we always be able to know it though?
 When the MessagePending header flows as a result of the MakeConnection
there's a "query expression" associated with the MakeConnection.
 In cases where the message on the transport request flow was not
a MakeConnection then I'm not sure what value the server would use to determine
if there are messages pending - i.e. what "query expression"
would it use to do the check?  Interestingly enough, I have been recently
wondering if we could use the wsa:From header for this purpose.  If
a one-way message was on the transport request flow, and since its a one-way
there was no response, could the server look at the wsa:From, and if it
used the RM anon URI, use that as an optimized MakeConnection?  In
other words, does wsa:From identify the sender?  WSA would seems to
say 'yes'.  This could save the overhead of another message exchange
in some cases.  Good thing WSA didn't kill wsa:From like they were
thinking.  :-)

thanks,
-Doug

Paul Fremantle <paul@wso2.com>

10/05/2006 06:32 PM

To	"ws-rx@lists.oasis-open.org" <ws-rx@lists.oasis-open.org>
cc
Subject	[ws-rx] MessagePending

Rereading the spec around MakeConnection, I realize
that we defined 
MessagePending as only applicable on a message flowing back on a 
MakeConnection backchannel. It seems to me that we could usefully add 
this message in cases where a response is flowing on a back channel.

For example. Suppose I have an interaction

1. GET1 ----->
<---- RESPONSE1

2. GET2----->
(response lost)

3. GET3----->
<------RESPONSE3

In 3, the Get will have an ack for response1, and the server can 
indicate that response 2 is missing.

We already have logic to decide when piggybacking of acks is 
appropriate. I believe the logic could be extended to decide when it was
ok to send back a MessagePending header:

* In the sequenceID case, it would be appropriate whenever the message
being sent back was part of the same Offered response sequence.
* In the URI case, it would be appropriate whenever the replyTo URI 
matched the MessagePending URI.

Paul