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On 14 Jun 2013, at 13:43, cotton-ben <ben.cotton(a)ALUMNI.RUTGERS.EDU> wrote:
Thanks for this reply, Mircea.
Very interesting approach. By dispatching a distributed executor back to
the node (node 0) that produced the pinned key affinity for the object's
natural key, we could indeed do an iterative search (from node 2) to find
the original 'myObject' in the pinned cache (on node 0). As you point out,
however, this approach is prohibitively costly -- we are effectively doing
an iterative search across nodes.
Again, we see the best approach as being to use the enhancement to the Key
Affinity Service API suggested in
https://issues.jboss.org/browse/ISPN-3112.
My
solution only makes sense if the vast majority of requests are processed by the node that
is aware of the key. Another thing you can do is have a replicated Cache holding the
mapping between the actual keys and the affinity keys. Whenever you need to lookup an obj
based on the actual key, you'd do a lookup in this cache(local) and then use this key
for getting the object you're after. This cache shoul be pretty small as well.
Once
*K getKeyForAddress(Address pinnedNodeAddress, K objectNaturalKey);*
is provided, we will be able to proceed as simply as follows:
//given that all nodes "know" that all birthday Entry(s) are pinned to Node
0
@t=0, from node=0, pin Entry to cache at Node 0
Object pinnedKey = getKeyForAddress(getAddress("Node0"),
"1962-08-10");
cache.put(pinnedKey,"Ben D. Cotton III birthday");
Later @t=1, from node =2, we can use the improved API (suggested in the
JIRA) from a 'foreign' node without any need to do a distributed, iterative
search, i.e.
Object pinnedKey = getKeyForAddress(getAddress("Node0"),
"1962-08-10");
Object birthdayCelebrant = cache.get(pinnedKey); //return "Ben D.
Cotton III birthday"
Of course, for us to be able to do this, the ISPN team would have to deliver
to us the API recommended in the JIRA
https://issues.jboss.org/browse/ISPN-3112. Don't you agree such an API
enhancement would be an awesome capability improvement for ISPN users
wishing to operate in a distributed fashion on pinned Caches? :-)
I understand your
requirements and also the usefulness of such a service :-)
I don't think it is possible to implement this without a severe limitation: if the
topology changes between the moment the key was created and the moment the method is
invoked, it would return an incorrect value(i'm not even sure that this woul work but
i have an idea at least). Whilst this might be enough for your application, it's not
sure it is a general purpose functionality for a fwk.
As always, thanks to you and this forum for its fine support,
Ben
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