[infinispan-dev] ISPN-30: DIST cache mode

[Manik Surtani]

On 16 Apr 2009, at 08:02, Bela Ban wrote:

> Thinking more about the wait time, this might be problematic:
>
>   * V1={A,B,C,D}
>   * K maps to C and D, repl-count=2
>   * V2={A,B,C}
>   * V3={A,B}
>   * If C and D crashed (say within 10 seconds), then we need to
>     rebalance K immediately upon receiving V2 because repl-count < 2
>
> Why not handle views immediately and rebalance elements ? We can  
> always think of optimizations later...

That is true - we need to think about shrinking clusters as well as  
growing ones.

> Rebalancing should occur a lot when starting the cluster, but at  
> this time, we don't have many elements in the cache anyway. During  
> operation, views should be infrequent. And, if we pick a good  
> consistent hashing algorithm, rehashing should only affect 1/N of  
> all elements anyway.

Yes.

> And remember: at the JGroups level, we can bundle views (= process  
> multiple LEAVE or JOIN requests together and generate only 1 view)  
> with GMS.view_bundling, this might help reducing churn without any  
> code changes, at least for the moment.

That's a good point.

Ok, I'll focus on immediate rehashing for now, and we'll look at wait  
times as an optimisation.

Cheers
--
Manik Surtani
manik at jboss.org
Lead, Infinispan
Lead, JBoss Cache
http://www.infinispan.org
http://www.jbosscache.org