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From James Strachan <>
Subject Re: ActiveCluster
Date Tue, 17 Jan 2006 18:06:59 GMT
On 17 Jan 2006, at 08:31, Rajith Attapattu wrote:
> Can somebody familliar with AC provide me some answers to the  
> following questions.
> 1. Why is the AC api tied to JMS??

We wanted a few simple APIs for a destination, a message and a  
message listener; so figured why not just reuse those trivial 3  
interfaces from JMS which are easy to implement however you like than  
make up yet another abstraction.

> I guess a simillar question was raised within the totem thread.
>     I was expecting a more abstract API independent of any platform  
> and then the implementation to be some sort of platform specific.
>     So there is a JMS impl on top of ActiveMQ or a JGroups impl.

We originally used another wrapper abstraction but figured it was  
much easier to just use a standard Java API and then wrapper it onto  
of other things like JGroups etc. Take a look at the interfaces of  
Destination & MessageListener & there's not a whole lot to it :) Then  
Message is pretty straight forward too.

>  2. Is there a doc that describes the architecture behind AC?? so I  
> can read up and better understand it.

Only whats on the wiki

> 3. Currently in addition to the default impl, ActiveSpace and WADI  
> is there any other impls/ use cases for AC?

ActiveMQ itself also uses it and so can ServiceMix (depending on how  
you wanna use it)

The use cases of ActiveCluster are when you want to support

* discovery of nodes arriving/disappearing from a cluster along with  
a small amount of per node state
* communicating with the entire cluster or with individual nodes
* performing an election strategy, so that you can have a single node  
in your cluster make a decision - such as 'can I take ownership of a  
session' or to perform a pessimistic lock or whatever.


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