Request for new feature

[Peter Antman <pra at mint.se>]

Hi,
this is a request for a new feature in XmlBlaster. You will have to
excuse me if this already works, I meen if the feature is already
available in XmlBlaster, and I have missed it.

Background:

Naively I have assumed that the following behaviour was supported by
XmlBlaster (since it seemded like something any MOM must have):

- A new client subscriber will only get new messages, not messages
   published before it logged in and started its subscription.

Why is this needed? Lets take the following scenario:

- We have a publisher which is publishing news of some sort. In the key
 the publisher not only ads a unique oid for every message, it also ad
 metainformation,such as headline, typ of subject, and perhaps even the
 body of the text.

- Clients wants to subscribe to these news, but through an XPATH query.
  The XPATH query is not placed against the oid since that is unique for
  every new message, but against the meta info.

- Only clients that are currently online should get messages that
  matched their query. A client that goes offline and then comes back
  should not recive any old messages.

- A future possibility would be to ad durable subscriptions so that
  clients that identifyes them self in a special way may get old
  messages (but not messages they have already recived).

Current behaviour:

I have not been able to get this type of behavour to work. Looking
through the code I get to understand XmlBlaster a little better. To me
it now seems as if there is a missmatch between the idea of specifying a
target in the key and specifying searchable metadata. If I get it, the
basic idea of XmlBlaster here is that messages with new content are
published to the same key. This is not what I want. 

A soulution:

I have implemented a workaround for this. It might not be the best one,
but it seems to work. It consists of the following two additions:

1. Ad tag <topic> to PublishQoS (a boolean).

2. If isTopic is true, then a published message will be removed after
   publishing in RequestBroker, ie:

    // NEW FEATURE, Removes message after publishing
	 if (publishQoS.isTopic()) {
	     if (Log.TRACE) Log.trace(ME, "Erasing published message");
	 
	     fireMessageEraseEvent(clientInfo, msgUnitHandler);
	     msgUnitHandler.erase();
	     msgUnitHandler = null;
	 }

This will only be done i Pub/Sub mode.

Ok, am I totaly of line here?

Comments please.

//Peter
-- 
Jobba hos oss: http://www.tim.se/weblab
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Peter Antman		 Technology in Media, Box 34105 100 26 Stockholm
Systems Architect	 WWW: http://www.tim.se
Email: pra at annons.dn.se	 WWW: http://www.backsource.org
Phone: +46-(0)8-506 381 11 Mobile: 070-675 3942 
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