On 06/28/2011 03:06 PM, Gordon Sim wrote:
On 06/28/2011 02:34 PM, Ken Giusti wrote:
This is great feedback - thanks to all.
I think the term "Message Groups" may not be the best term to use as
the name for this feature, as proposed in the qip. I agree that the
term "Message Group" has historically implied a sticky consumer - at
least that's what Google leads me to believe.
The qip wasn't clear regarding the priority of "sticky consumer"
support - as Gordon correctly points out, this qip should lay the
foundation for supporting both behaviours, as (I believe) there is
value in both approaches.
So: 1) I'd like to rename the QIP - is there a better term to use for
the "non-sticky" case than "Message Groups"?
I actually quite like 'Message Groups' as a term, I just think there are
different ways of treating a group.
I think that rather than 'sticky' and 'non-sticky' we really just have two modes
of stickiness, i.e. two scopes for the association between group and consumer.
In the first mode the group is tied to a consumer only while that consumer has
outstanding, unaccepted messages.
This is sufficient to guarantee strict fifo processing in a group.
It also meets Marnie's requirement of having the 'group as a whole' processed by
the client without having to have any explicit end-of-group signal that the
broker needs to recognise. The client implicitly signals the end-of-group when
it acknowledges the messages in the group.
The second mode extends the scope of the association. The group here is tied to
a consumer for the life of that consumer. This meets Rob's further requirement
of allowing any state required and/or built-up during processing of the group to
be contained within the single consumer.
It seems to me that the first mode contains the second: the client can simply
delay acknowledgement of at least one message until it is happy that the entire
group is processed (which could be the entire life of the consumer, or some
shorter span at the clients discretion.)
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