[infinispan-dev] Partial state transfer in Infinispan

[Sanne Grinovero]

Hi Bela,

2011/6/1 Bela Ban <bban at redhat.com>:
> We currently use JGroups' partial state transfer to transfer individual
> caches from one Infinispan instance to another.
>
> Since I got rid of partial state transfer in JGroups 3.0, and don't like
> to add it back, I'd like to know whether this is still needed.
>
> I thought that we currently require the same set of caches to be
> available in all Infinispan instances, and the reason (IIRC) was that
> distribution wouldn't work if we have caches 1 and 2 available on
> instances A and B, but not on C, because consistent hashing distributes
> the data based on views, and we didn't want to have to keep track of
> individual caches...

Well I really don't like this limitation in Infinispan and was
actually hoping that we could remove it at some point.
Imagine the scenario in which you have a running cluster, and at some
point the new release of your application needs an additional cache:
there's no way to start a new node having this new cache.
Also right now when an application starts, it's possible with the
proper timing that it joins the cluster before having defined and
started all caches (starting the cachemanager and the caches is not an
atomic operation), basically failing to start because of this
limitation.

Maybe it's still possible to build such a thing on top of non-partial
state transfer? As it doesn't exist, we didn't design it.

>
> Why are we actually using JGroups' state transfer with replication, but
> use our own state transfer with distribution ?

I don't know, but guess it's because each node has a different set of
keys so no node has the same state as another ?

Cheers,
Sanne

>
> Opinions ?
>
> --
> Bela Ban
> Lead JGroups / Clustering Team
> JBoss
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