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From Geir Magnusson Jr. <ge...@adeptra.com>
Subject Re: questions on RunTime Singleton
Date Wed, 18 Dec 2002 16:27:47 GMT

On Wednesday, December 18, 2002, at 11:11 AM, Hanasaki JiJi wrote:

> I had thought there were issues with the same application running on 
> multiple servers using singletons becuase each server has its own JVM 
> yet a singleton can only exist in one JVM.

Ignoring the complication that classloaders will bring into this 
discussion, yes,  only one singleton can exist in a JVM.  However, each 
JVM can have their own, as there is no 'conversation' between the JVMs 
about this.

geir


> ???
>
> Geir Magnusson Jr. wrote:
>> On Wednesday, December 18, 2002, at 10:26 AM, Hanasaki JiJi wrote:
>>> Going through the Velocity API's and example code, there are several 
>>> references to RuntimeSingleton.
>>>
>>> Is this class an issue for clustered/loadBalanced servers running 
>>> velocity applications?  If so, how how can the this be addressed?
>> ?
>> I don't understand the question.  If you are doing load balancing, 
>> and want to keep a users state in a session, then it doesn't matter 
>> if you use the singlton or not - you have to take care of the problem 
>> with either a shared store for state info, or a balancer that keeps 
>> sessions sticky.
>> The singleton just means that in a given JVM (or a webapp) all users 
>> of it share the same instance, and thus the same configuration.  You 
>> may find this useful (to share cached templates) or not (if you want 
>> different configurations of the velocity engine at the same time...)
>
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-- 
Geir Magnusson Jr                                   203-355-2219(w)
Adeptra, Inc.                                       203-247-1713(m)
geirm@adeptra.com


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