[jboss-cluster-dev] Consistent Hashing in mod_cluster

[Brian Stansberry]

On 04/13/2010 04:43 AM, Manik Surtani wrote:
>
> On 9 Apr 2010, at 16:00, Brian Stansberry wrote:

>>
>> Hmm, an issue is if the caches involved in the overall picture (e.g.
>> httpsession cache and "chat state" cache) end up using different
>> CacheManagers/JGroups Channels. This would quite likely happen (see
>> http://community.jboss.org/thread/149868 for discussion why). If that's
>> the case, the views between the channels could end up slightly different
>> -- e.g. servers A and B are booting at the same time, so due to slight
>> differences in the boot, Channel for HTTPSession cache ends up with view
>> {A, B} and Channel for "chat state" cache ends up with {B, A}. In that
>> case I wouldn't expect there to be a reliable, performant way to ensure
>> affinity, since the view is a major factor in the hashing algorithm.
>
> Yes, it would not be useful at all if the 2 components end up with
> different views. It would only make sense if the web session cache and
> the SFSB session cache share the same CacheManager/Channel.
>

OK, so JGroups SCOPE is going to be important here.

-- 
Brian Stansberry
Lead, AS Clustering
JBoss by Red Hat