On Feb 13, 2008, at 11:13 PM, David Sitsky wrote:
I just noticed while looking at Queue.removeSubscription(), that it
goes through pagedInMessages, and effectively redelivers all
messages that were locked by the removed subscription.
My question is why is this necessary? From my understanding in the
code (which may be flawed), these messages will be present in the
pending lists of all the other current subscribers, so they should
eventually dispatch this message since the messages are now unlocked.
I know we call node.incrementRedeliveryCounter() to indicate that
the message is being redelivered - but it seems to me that we can
avoid redelivering these messages which seems desirable, since some
consumers may see the same message twice.
--
Cheers,
David
Nuix Pty Ltd
Suite 79, 89 Jones St, Ultimo NSW 2007, Australia Ph: +61 2 9280
0699
Web: http://www.nuix.com Fax: +61 2 9212
6902
The reason for redelivering messages when a subscription is removed is
because other subscriptions may have originally disocunted those
messages because they were locked when they came to try and dispatch
them.
The whole Queue dispatch model is not very scalable because each
message is being delivered to each subscription - this, I think was
done because it made the implementation of exclusive consumer easier.
I'm currently moving away from this model - to decide at Queue
dispatch time which subscription should get the message - just like a
- well a Queue!
cheers,
Rob
