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From Dain Sundstrom <>
Subject Re: Effectiveness of WADI's Design and Implementation Comforted
Date Fri, 19 Oct 2007 00:19:50 GMT
I agree about the annotation thing.  Would it be difficult change the  
design to have some reasonable defaults, and only use annotations (or  
xml) for overrides?


On Oct 18, 2007, at 3:49 PM, Jeff Genender wrote:

> Gianni,
> What you have done is very cool.  I guess my only comment is that  
> what I
> am reading is that the annotations force a lock to the clustering
> engine, as opposed to being somewhat transparent by swapping out the
> clustering manager.
> Therefore, my application code needs these annotations coded as a part
> of it.  In otherwords, in order for me to leverage the fine grained
> capabilities of WADI, my application needs to be coded with the WADI
> annotations.  Did I read that correctly?
> Regardless...its pretty cool stuff.  We should talk about the
> contract/interface for openejb...I look forward to working with  
> you ;-)
> Jeff
> Gianny Damour wrote:
>> On 17/10/2007, at 11:53 PM, Jeff Genender wrote:
>>> Gianny Damour wrote:
>>>> Excerpt of the conclusion:
>>>> "
>>>> The effectiveness of the design and implementation of WADI's  
>>>> distributed
>>>> session lookup engine and replication engine is further  
>>>> comforted by the
>>>> observed average response times and scalability characteristics.
>>>> For the considered scenarios, WADI performs better than Terracotta,
>>>> which is not really surprising as...
>>> If I may comment here...Without fine-grained clustering  
>>> capabilities, I
>>> have a hard time believing that WADI can outperform Terracotta.
>>> Especially with large objects...WADI would push over the entire  
>>> object
>>> each time, where Terracotta would only ship the changed members.   
>>> If you
>>> are going to publish the numbers you did, you probably should  
>>> explain
>>> what is getting pushed across.
>> Hi,
>> I believe you simply skimmed through what I have been writing:  
>> firstly,
>> I did provide a description of the state stored in session. Secondly,
>> your comment about large objects and the inadequacy of WADI's  
>> design to
>> handle them is clearly and explicitly discussed in the  second  
>> paragraph
>> of the conclusion. As redundancy of information is not much of a  
>> problem
>> for theoretical clustering discussions, I am reiterating: WADI does
>> provide a fine grained replication mechanism, which is able to track
>> field updates or method executions and replay them against  
>> replicas. If
>> you are interested by this kind of stuff, then please feel free to  
>> have
>> a look to this WIKI page -
>> At this stage, the delta replication stuff is under performing and
>> resource intensive: to give you an idea, its average response time is
>> 6.10ms for the third test scenario (average response time for default
>> replication mechanism is 4.77ms for WADI and 6.36ms for Terracotta).
>> Once again, as a preliminary comment to Ari's response, this is a
>> scenario with HTTP session stickiness on. After this week-end, the
>> performance for fine-grained replication should improve  
>> significantly. I
>> intend to: get ride of native reflection; index constructor, field  
>> and
>> methods description for really fast packaging on wire and resolution
>> when reading back from a byte stream; and re-use reflective invokers
>> (CGLIB FastMethod/Constructor and ASM customed field updaters).
>> FWIW, I do not see support of large objects as crucial as you for Web
>> solutions. Even if I spent a couple of months working on wadi-aop to
>> provide this feature, it was more with the ultimate goal to  
>> leverage it
>> for efficient distributed caching than HTTP session replication. I  
>> truly
>> believe that large scale Web solutions requiring HA have to be  
>> designed
>> with this constraint in mind; with this constraint in mind, keeping
>> session size small sounds reasonable.
>>>> "
>>>> If people are interested by clustering development, then please  
>>>> respond
>>>> as I will resume some Geronimo clustering work and could really  
>>>> use a
>>>> hand.
>>> I am in the midst of getting OpenEJB clusterable.  I would be  
>>> happy to
>>> combine forces and get clustering finished up for G ;-)
>> Great! Will post back to the dev@ list as soon as I resume Geronimo
>> clustering work.
>> Thanks,
>> Gianny
>>>> Thanks,
>>>> Gianny

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