[jdev] Cancelling an iq query

[Ralph Meijer]

On Mon, Aug 29, 2005 at 03:00:42PM -0700, Ralph Giles wrote:
> On Mon, Aug 29, 2005 at 08:39:33PM +0200, Ralph Meijer wrote:
> [..]
>
> > Sure, you could use JEP-0050 for that, but that wasn't the complete
> > problem of the other Ralph. He wanted to be able to cancel a placed
> > request *and* still receive results asynchronously. Or do you propose
> > not replying to the original <iq/> until the request has indeed been
> > completed or cancelled?
> 
> Actually, that would work for us. It's nice having teh query 
> sanity-checked, but the important thing is to be able to cancel
> and/or modify. It's fine if the reply comes back either when
> the results are available, or after the ad hoc cancel command
> has killed the query.
> 
> I'm not clear that it's ligher weight than the transaction
> semantics though...

Ok, JEP-0050 adds some extra processing. I might now be tempted to
do the following:

Request:

  <iq from='client at example.com/client'
      to='service.example.com'
      type='set' id='H_2'>
    <transaction xmlns='http://example.com/transaction'>
      <query id='query_5'>
        ...
      </query>
    </transaction>
  </iq>

Response when not cancelled, no need for the actual query identifier:

  <iq from='service.example.com'
      to='client at example.com/client'
      type='result' id='H_2'>
    <transaction xmlns='http://example.com/transaction'>
      <results>
        ...
      </results>
    </transaction>
  </iq>

Cancel request:

  <iq from='client at example.com/client'
      to='service.example.com'
      type='set' id='H_3'>
    <transaction xmlns='http://example.com/transaction'>
      <cancel id='query_5'/>
    </transaction>
  </iq>

Yielding:

  <iq from='service.example.com'
      to='client at example.com/client'
      type='result' id='H_3'/>
  <iq from='service.example.com'
      to='client at example.com/client'
      type='error' id='H_2'>
    <transaction xmlns='http://example.com/transaction'>
      <query id='query_5'>
        ...
      </query>
    </transaction>
    <error type='cancel'>
      <undefined-condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
      <cancelled xmlns='http://example.com/transaction#error'/>
      <text xmlns='urn:ietf:params:xml:ns:xmpp-stanzas' xml:lang='en'>
        The referenced query has been cancelled.
      </text>
    </error>
  </iq>

or in case the request already finished; the H_2 reply is then as above,
in the happy path:

  <iq from='service.example.com'
      to='client at example.com/client'
      type='error' id='H_3'>
    <transaction xmlns='http://example.com/transaction'>
      <cancel id='query_5'/>
    </transaction>
    <error type='cancel'>
      <item-not-found xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
      <completed xmlns='http://example.com/transaction#error'/>
      <text xmlns='urn:ietf:params:xml:ns:xmpp-stanzas' xml:lang='en'>
        The referenced query has already been completed and cannot be
        cancelled.
      </text>
    </error>
  </iq>

-- 
Groetjes,

ralphm