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From Simon Pabst <>
Subject mod_jk round robin problem & stateless session beans
Date Mon, 14 Jul 2003 21:17:28 GMT
We have the following setup:
One Apache with HTTPS/SSL with mod_jk (one load balancer, sticky sessions 
on) in front
Eight Tomcats in back

Round Robin doesn't work, but instead the Users are distributed on the 
Tomcats like this:

Tomcat No.| User Count (approx. daily)
T1		70
T2		30
T3		15
T4		6
T5		1
T6		0
T7		0
T8		0

This occurs both with Apache1.3.27/mod_jk1.2.x and Apache2.0.45/mod_jk2.x
(mod_jk 1 and 2 built from source of jakarta-tomcat-connectors-4.1.24-src 
and later also of tomcat-connectors-1.1M1-src).

Anyone ever experienced something similar or has any insight in this?

According to the application developer the application is using stateless 
session beans.
(Since i'm just a stupid server admin and no Java Programmer i don't really 
now what that is :-)

I tested the Load Balancing with the Tomcat SessionExample and round robin 
seemed to work fine.
If i switch of sticky session round robin also works fine, but not the 
application :-)

Do stateless session beans even work with mod_jk's sticky session stuff?
(in this discussion
somebody said:
"if the application stores the stateless session bean in the httpsession, 
the application risks having all of the workload to only one of the nodes 
in the cluster")

If anyone knows how sticky sessions of mod_jk(2) work, please enlighten me :-)
Is it IP based in any way, are Cookies involved or JSESSIONID or anything else?
Could it be a problem that all Tomcats are on the same machine? (i tested 
this with pseudo network addresses for each Tomcat too, but 
didn't help either)
Could HTTPS cause any troubles for this?

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