[standards-jig] JEP-0024: Publish/Subscribe - Topic based messaging

DJ Adams dj.adams at pobox.com
Sat May 11 15:31:25 UTC 2002


On Sun, Apr 28, 2002 at 10:25:27AM -0700, Iain Shigeoka wrote:
> Time outs on messages is a good idea.  My scenario though is a bit different. 
> Imagine we have a queue with 3 subscribers online.  A message is published. 
> The server/broker pushes the message out to all three.  Now one subscriber goes
> offline but remains subscribed.  A message is published.  2 subscribers are
> online, the messages is pushed out to the two subscribers, and stored for the
> other subscriber.  One of the 2 subscribers disconnects but remains subscribed.
>  Another message is published.  It is directly delivered to the remaining
> online subscriber, but is stored for delivery to the 2 offline subscribers. 
> The first message in the queue is waiting for one subscriber to take it.  the
> second message in the queue is waiting for 2 subscribers to take it.
> 
> The server must be able to track and manage these "reference counts" on
> messages waiting to be delivered.  In most large servers, I would imagine you
...

I would posit that it's not the pubsub component's remit to handle 
storing and forwarding of messages. That is something to be addressed
outside of pubsub. We already have storing and forwarding of message
elements in a JSM context (and since 1.4.2 in a component context), 
and discussed the (real, IMHO[1]) possibility of selectively storing
and forwarding of IQs.

I want to avoid reinventing Jabber inside subsets of Jabber.

Cheers
dj

[1] I've an experimental hack to mod_offline to do this



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