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From Jules Gosnell <>
Subject Re: Replication using totem protocol
Date Fri, 13 Jan 2006 11:11:02 GMT
further thoughts at bottom....

Jules Gosnell wrote:

> wrote:
>>> wrote:
>>>> Well, you guys let me know if I can help you in any way.
>>> Keep on talking ;-)
>> Okay. I will ask you a question then. What are you doing as far caching
>> entity beans?
> In terms or replication or some form of distributed invalidation, I'm 
> not aware that this has been discussed yet.
> This is another one for the forthcoming doc - briefly :
> If you cluster an entity bean on two nodes naively, you lose many of 
> the benefits of caching. This is because neither node, at the 
> beginning of a transaction, knows whether the other node has changed 
> the beans contents since it was last loaded into cache, so the cache 
> must be assumed invalid. Thus, you find yourself going to the db much 
> more frequently than you would like, and the number of trips increases 
> linearly with the number of clients - i.e. you are no longer scalable.
> If you can arrange for the cache on one node to notify the cache on 
> other nodes, whenever an entity is changed, then the other caches can 
> optimise their actions, so that rather assuming that all beans are 
> invalid, they can pinpoint the ones that actually are invalid and only 
> reload those.
> You could go one step further and send, not an invalidation, but a 
> replication message. This would contain the Entity's new value and 
> head off any reloading from the DB at all....
> All of this needs to be properly integrated with e.g. transactions, 
> locking etc...
> Perhaps Totem might be useful here ?
ActiveSpace (in incubator) may already have support for this sort of thing ?
If you had a working clustered cache with a cache loader pointing at the 


> Jules

"Open Source is a self-assembling organism. You dangle a piece of
string into a super-saturated solution and a whole operating-system
crystallises out around it."

 * Jules Gosnell
 * Partner
 * Core Developers Network (Europe)
 * Open Source Training & Support.

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