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From Jules Gosnell <>
Subject Re: [wadi-dev] Re: Clustering - WADI/ActiveSpace Synergy...
Date Mon, 30 Jan 2006 11:00:39 GMT
James Strachan wrote:

> On 30 Jan 2006, at 10:29, Jules Gosnell wrote:
>> James Strachan wrote:
>>> On 30 Jan 2006, at 10:06, Jules Gosnell wrote:
>>>> Finally, as discussed with James on numerous occasions, we  should  
>>>> look at how WADI's pessimistic locking and  PartitionManager might  
>>>> be componentised so that they can be  plugged into AS to provide  
>>>> Cache and Space users, who are not  interested in location- 
>>>> independance, with a pessimistic approach  and/or a partitioned  
>>>> clustering substrate...
>>> BTW I don't see using a pessimistic lock as being very useful for  
>>> a  cache; typically in a JCache scenario you are caching state  that 
>>> is  stored in some database/system; so if you really want a  
>>> pessimistic  lock you should lock the database (they are very good  
>>> at doing  distributed locks) rather than having a pessimistic lock  
>>> in a cache  which is a different lock to where the actual data is.
>> Agreed - but in the case of a distributed session, it may not be  
>> mapped to a database.... - I guess we are not a typical JCache  
>> scenario ?
> Exactly. JCache is usually used for distributed caching of persistent  
> state. So for most users of JCache, pessimistic locking has no real  
> value.
> The exception to this rule is for folks who want to use JCache as a  
> database (being the master copy of the state) which is usually as a  
> result of folks trying to solve the distributed-session-state  
> problem. But its much better IMHO to just solve the distributed  
> session state problem correctly than turn JCache into a database :)
not sure that I follow you here - so you are saying 'don't use jcache 
for distributed sessions' ? - or am I misunderstanding ? How would you 
'solve the distributed  session state problem correctly' ?

thanks for the clarification,


> James
> -------

"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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