Re: Effectiveness of WADI's Design and Implementation Comforted

[Dain Sundstrom]

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?

-dain
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 -
http://docs.codehaus.org/display/WADI/5.+Delta+Session+Replication.

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