[Openais] Re: [saf-open] Open channels, retained events, cluster partition merges.

John Cherry cherry at osdl.org
Thu Feb 10 13:43:30 PST 2005

On Thu, 2005-02-10 at 11:22 -0800, Mark Haverkamp wrote:
> On Thu, 2005-02-10 at 12:15 -0700, Steven Dake wrote:
> > Mark
> > 
> > I wasn't contributing during the specification of this wording of the
> > unlink so I am unsure.  This question might be appropriate for the
> > saf-open list though.  Perhaps some of the saf spec developers may have
> > some ideas.
> > 
> Yes, that is the very reason that i copied that list on my mail.

Sorry for lurking on this list and chiming in now.

The notion of merging or resolving retained events can be solved a
number of ways.  Solutions depend on the underlying cluster model.  The
openais model is that a cluster can partition into multiple active
clusters.  When these clusters merge, retained events need to be
reconciled across active cluster instances.  If the cluster model is one
where only one active partition of a cluster exists, the problem is much
easier to solve and merging assumptions do not need to be made.

My question is simpler.  Why do we have the requirement for retained
events?  Is there a usage case for retained events that could be
articulated?  Will any clustered applications actually make use of
retained events?

In the openais cluster model, it is possible that a node would join the
cluster at time X and then have to service an event that happened some
amount of time before X with potentially other events being posted and
possibly serviced between those two points in time.  A retained event
would essentially have to be sequence-independent from other events.
Would this stipulation of sequence-independent events have any impact on
applications servicing retained events?  Again, a usage case would be
very useful.


> Mark.
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