This document summarizes the steps to configure Apache load balancing with multiple Tomcat instances. The key requirements are Java, Tomcat, Apache web server and the mod_jk module. Configuring mod_jk involves enabling it in Apache, and creating configuration files for the workers, URI mappings and mod_jk. The worker file defines each Tomcat instance with its port and host. The URI file maps paths to workers. The Tomcat instances need their ports and jvmRoute configured to match the worker definitions. Finally, starting Apache and the Tomcats verifies load balancing by checking session handling across multiple access sessions.

1. Apache Load Balancing :
Basic SW Requirements :
1. java
2. Tomcat
3. Apache web server
4. mod_jk
Pre-Check :
1. Java home/path settings in environment
2. Test and ensure tomcat instance / httpd [Apache web server] is running .
Basic Configuration:
1. enable mod_jk in apache configuration file . Ensure in below paths and files :
1. /etc/httpd/modules (or) /usr/lib64/httpd/modules/
2./usr/libexec/
2. need to create the following files to integrate tomcat app's with apache httpd
server under /etc/httpd/conf.d/.
1. worker.properties
2.uriworkermap.properties
3. mod_jk.conf
worker.properties file format :
worker.list=lb,status
worker.tomcat1.port=8009
worker.tomcat1.host=localhost
worker.tomcat1.type=ajp13
worker.tomcat1.lbfactor=1
worker.tomcat1.redirect=tomcat2
worker.tomcat2.port=8079
worker.tomcat2.host=localhost
worker.tomcat2.type=ajp13
worker.tomcat2.lbfactor=1
worker.tomcat2.redirect=tomcat1
worker.lb.type=lb
worker.lb.balance_workers=tomcat1,tomcat2
worker.lb.sticky_session=True
worker.lb.sticky_session_force=True
worker.status.type=status
worker.localhost.host=localhost
Note :
1. while enabling LB we need to declare lb worker in worker.list [It is not workers.list]
2. Change the native AJP port as per the infrastructure security policy in tomcat server.xml
files . And ensure the tomcat is running on that port while running .
[netstat -nap |grep java]
3. update the details for each instances as per the above format .
4. Finally declare loadbalancer with the above attributes [balance_workers[it is not
balance_worker],sticky_session.sticky_session_force ]
5. declaring the status worker to check the status of Load Balancing

2. mod_jk.conf configuration:
LoadModule jk_module modules/mod_jk.so
JkWorkersFile conf.d/worker.properties
JkMountFile conf.d/uriworkermap.properties
JkLogFile /var/log/mod_jk.log
JkLogLevel info
JkLogStampFormat "[%a %b %d %H:%M:%S %Y] "
JkOptions +ForwardKeySize +ForwardURICompat -ForwardDirectories
JkRequestLogFormat "%w %V %T"
JkShmFile logs/jk.shm
Note :
1. 1st line including the mod_jk.so with httpd
2. JkWorkersFile Including the worker.properties file
3. JkMountFile we are declaring the worker and mounting point details .
4. 4th line saying the log file location
5. Other attributes saying the log formates and final line is about memory details .
uriworkermap.properties file :
#/admin/*=lb
#/manager/*=lb
#/jsp-examples/*=lb
#/servlets-examples/*=lb
#/examples/*=lb
#/jk-manager=status
/* =lb
/status =status
Note :
Declaring the mount points with the specific worker details
We are using with load balancing so we can declare with loadbalancer worker [lb] .
Loadbalancer worker will take care the distribution of the load and session status
Tomcat configuration[server.xml]:
1. we need to change the native ports in tomcat server.xml file as per the
requirements
[We have used here 8009 & 8079]
ex :
<Connector port="8009" protocol="AJP/1.3" redirectPort="8473" />
in tomcat1
<Connector port="8079" protocol="AJP/1.3" redirectPort="8473" />
in tomcat2
2. change the jvmRoute name as per the workers declaration.
Ex:
in tomcat1
<Engine name="Catalina" defaultHost="localhost" jvmRoute="tomcat1">
in tomcat1
<Engine name="Catalina" defaultHost="localhost" jvmRoute="tomcat2">

3. Final steps :
1. Once done all the configuration as per the above details start the tomcat instances
and apache server . Check the service status and log details for the information .
2. To verify the session status in load balancing Please create index.jsp with
identification [page color/ content different ] in $TOMCAT_HOME/webapps/ROOT/
3. access the server in two different session and confirm the load balance status. It
need to handle the sessions separately.
K.KarthiKeyan