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From Jeff Genender <>
Subject Re: Effectiveness of WADI's Design and Implementation Comforted
Date Thu, 18 Oct 2007 22:49:04 GMT

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 ;-)


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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