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From James Strachan <james.strac...@gmail.com>
Subject Re: [wadi-dev] Re: Clustering - WADI/ActiveSpace Synergy...
Date Mon, 30 Jan 2006 10:52:08 GMT
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 :)

James
-------
http://radio.weblogs.com/0112098/


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