There are several ways to achieve scalability:
- Use a session aware external load balancer
- Use the tomcat loadbancer
mod_jk has a loadbalacer that implements sticky sessions
(AFAIK the loadbalancer currently just works with 3.2/3.3)
- Use distributed sessions
I don't know the state for tomcat. But there is something going on.
- Scale horicontal
- deploy apache, tomcat, database on different machines.
- Scale vertically
Depending on the kind of application you have, you can deploy
differents part of your application on different machines.
It depends on you application if you need to keep the session
between these parts.
- Scale with hardware
Buy or rent a bigger/faster machine or improve your existing
one. (Find out the bottlenecks and improve)
There are many solutions around from 1 to several hundred
processors with different architectures.
Depending on your needs this can be much cheaper in TCO than
a second machnine. (With a second machine you double the
administrative overhead, you need to think about distributed
backup, the failure rate will increase)
- Scale with optimizing
Make your application faster on the same hardware.
If you want to scale by deploying tomcat to several machines
this is not always transparent to your application. Some
examples:
- If you create unique id's, you must make shure that they are
unique across instances.
- If you store information in the file system you have to enshure
- that it is acsessible to the current session
no matter on which machine the session currently is
- that if you use sticky sessions, this information is not needed
by other sessions or it is available on all machines.
> -----Ursprüngliche Nachricht-----
> Von: Soefara Redzuan [mailto:[EMAIL PROTECTED]]
> Gesendet: Donnerstag, 11. April 2002 04:56
> An: [EMAIL PROTECTED]
> Betreff: Designing for scalability ?
>
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