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
