There are several options you can use for scalability.

A software solution is to use Windows 2000 Advanced Server.  In a
clustered environment, there is a parameter called Affinity.  Affinity
will maintain the client's session to one particular server in the
cluster.  Advanced Server works by assigning the cluster 1 IP address
and each individual server a secondary IP address.

A hardware solution is to use a load balancer. Coyote Point makes a good
load balancer (Equalizer 250) which will maintain the session to the
appropriate server.

Kurt Seidensticker
HostJSP.com, HostJ2EE.com
PROMINENT SOFTWARE GROUP, INC.
4TH FLOOR
10 N MARTINGALE RD
SCHAUMBURG, IL 60173
ph:     847-466-1010
fx:     847-466-1101


-----Original Message-----
From: Soefara Redzuan [mailto:[EMAIL PROTECTED]] 
Sent: Wednesday, April 10, 2002 9:56 PM
To: [EMAIL PROTECTED]
Subject: Designing for scalability ?


If one day you suspect that one Tomcat server will not be sufficient,
and 
you will have to employ 2 or more Tomcat servers running on separate 
machines, how can we allow for scalability ?

For example, using simple DNS round-robbin to offload requests between 
servers, a first request might arrive at one server and a Session object

created. But if the subsequent request (from the same client) arrives at
a 
different server, that Session will not be found, will it ?  (As far as
I 
know, there is no method to store Sessions in a common database used by 
several servers)

What steps are people taking to allow for scalability in their
applications 
? Are there any steps that can be implemented at initial development
which 
may save time further down the road ?

Thank you, Soefara.

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