[infinispan-dev] KeyAffinityService (nice) - 2 recommendations

[Mircea Markus]

On 16 May 2013, at 19:12, cotton-ben <ben.cotton at ALUMNI.RUTGERS.EDU> wrote:

> Hi,
> 
> First, nice work on org.infinispan.affinity.KeyAffinityService  ... May I
> make 2 recommendations.
> 
Thanks for the feedback!
> 1.  Add to the interface an overload =
> 
>          *K   getKeyForAddress(Address address, K otherKey);    /*compute
> address specific version of otherKey*/*
makes sense, can you please raise a JIRA for that?
https://issues.jboss.org/browse/ISPN
> 
> 2.  Provide documentation that *explicitly* motivates users to
> understand/exercise the differences (and compatibilities) of the
> KeyAffinityService API and the Grouping API.  Now, that I have some
> competency using KeyAffinityService, I am not sure of which use case would
> call for my using org.infinispan.distribution.group.Grouper API (unless
> maybe to manage a collection of nodes that have custody of key-set(s) pinned
> to it by the KeyAffinityService?).

The key affinity might be lost during topology changes. E.g. if k1 maps to node N1, if you add another node to the system k1 can me migrated to N2. With grouping you have the guarantee that the same node (you don't know really know which one) will host all the data from the same group even after topology changes.

> 
> Thanks,
> Ben
> 
> 
> 
> 
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Cheers,
-- 
Mircea Markus
Infinispan lead (www.infinispan.org)