I'd go the opposite direction, I will do stateless before attempting any
kind of replication or distributed cache.
The scalability of a stateless application will outscale any replicated
app any day, since your fail over options are so much more simplified.
Filip
Dwayne wrote:
Have you considered distributed caching for session replication? I avoid
stateless like the plague.
There are several tools out there for this, but my favorite (because they
are open source) is Terracotta. It clusters the JVMs.
Native clustering in Tomcat putters out, in my experience, after 3 nodes.
With Terracotta, I dropped in the code and now am clustering 5 nodes and
getting a lot higher TPS.
I think it is worth the hour it took me to implement it and I didn't have to
change my code at all, just write a short XML and drop some tags around what
I wanted to distribute.
Get it at terracotta.org. The support docs do not say they support Tomcat 6
yet, but I have yet to hit any bugs (3 weeks in).
On 8/24/07, lightbulb432 <[EMAIL PROTECTED]> wrote:
Although the debate between session replication vs stateless can't be
definitively solved and depends on the application, I'd like to hear about
your experiences with both. How are you designing your current
applications,
and what implications has the choice that you might not have expected -
would you do anything differently if you could?
I ask because I'm still unsure about whether to decrease memory usage by
increasing database usage (or bandwidth usage if sending state back to the
client) by going stateless at the application tier.
Stateless
Are there any people using stateless application tiers with transactions
that are inherently stateful, such as wizard-type screens or other
business
processes or workflows? How'd that turn out?
Did you choose to move this state to the client (through cookies) or to
the
database?
Session replication
For session replication in Tomcat 6, what's the ideal replication group
size
in general? Would you ever want to set it to more than 2 instances?
(Because
for any more, then you'd have a lot more overhead in transferring state
back
and forth to even more other instances...)
With session replication between 2 machines, are you effectively reducing
the capacity of each server, at least in terms of memory, by 50%?
Hopefully
I'm looking at it the wrong way, because it not, I'm not really liking the
session replication idea if I'm decreasing hardware usage by half.
Thanks.
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