How to Configure Tomcat/JBoss and Apache HTTPD for Load Balancing and Failover

In this post we will see how to setup a load balanced JBoss or Tomcat environment with the fail-over capability.

This post assumes that both Jboss/Tomcat and Apache httpd are setup and running properly.

Configure Apache Httpd

Step 1: Configure apache’s workers.properties

Go to /usr/local/apache2/conf/extra and open workers.properties and configure the properties indicated in bold.

# for mapping requests
# The configuration directives are valid
# for the mod_jk version 1.2.18 and later
#
worker.list=loadbalancer,status

# Define node
# modify the host as your host IP or DNS name.

worker.node.port=8009
worker.node.host=192.168.0.3 #(IP or DNS name of the server on which Jboss is running)
worker.node.type=ajp13
worker.node.lbfactor=1

worker.node2.port=8009
worker.node2.host=192.168.0.4 #(IP or DNS name of the server on which Jboss is running)
worker.node2.type=ajp13
worker.node2.lbfactor=1

# Load-balancing behaviour
worker.loadbalancer.type=lb
worker.loadbalancer.balance_workers=node,node2
worker.loadbalancer.sticky_session=1
worker.status.type=status

The property balance_workers is used to specify the nodes to load balance. For example, if we specify only ‘node’, all requests will be routed to the server named ‘node’. Modify this to test that requests are going to both servers.

Step 2: Configure mod-jk.conf

Go to /usr/local/apache2/conf/extra and open mod-jk.conf and configure the bold properties according to your requirements.

#Load mod_jk module
# Specify the filename of the mod_jk lib
LoadModule jk_module modules/mod_jk.so

# Where to find workers.properties
JkWorkersFile conf/extra/workers.properties

# Where to put jk logs
JkLogFile /var/apache/logs/mod_jk.log

# Set the jk log level [debug/error/info]
JkLogLevel debug

# Select the log format
JkLogStampFormat "[%a %b %d %H:%M:%S %Y]"

# JkOptions indicates to send SSK KEY SIZE
# Note: Changed from +ForwardURICompat.
# See http://tomcat.apache.org/security-jk.html
JkOptions +ForwardKeySize +ForwardURICompatUnparsed -ForwardDirectories
JkOptions +FlushPackets
# JkRequestLogFormat
JkRequestLogFormat "%w %V %T"

# Mount your applications
JkMount /* loadbalancer

# You can use external file for mount points.
# It will be checked for updates each 60 seconds.
# The format of the file is: /url=worker
# /examples/*=loadbalancer
JkMountFile conf/extra/uriworkermap.properties

# Add shared memory.
# This directive is present with 1.2.10 and
# later versions of mod_jk, and is needed for
# for load balancing to work properly
# Note: Replaced JkShmFile logs/jk.shm due to SELinux issues. Refer to
# https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=225452
JkShmFile /var/run/jk.shm

# Add jkstatus for managing runtime data
<Location /jkstatus/>
  JkMount status
  Order deny,allow
  Deny from all
  Allow from 127.0.0.1
</Location>

The JkMount /* loadbalancer indicates that all requests are to be routed through the load balancer.

Step 3: Go to /usr/local/apache2/conf and edit httpd.conf

Add

Include conf/extra/mod-jk.conf

to the end of the file.

Configure Tomcat/JBoss

These settings need to be made for each of the nodes we intend on placing behind the load balancer.

We need to modify the server.xml file which is located at

• For Tomcat
  • ../apache-tomcat/conf/
• For JBoss
  • ../jboss-5.1.0.GA/server/default/deploy/jbossweb.sar 

Edit the following tag:

<Engine name="jboss.web" defaultHost="localhost" jvmRoute="node">

where the jvmRoute attribute is configured to ‘node’ (which is the name we gave the first worker while configuring workers.properties.)

Next, locate the following tag and edit the port to be the same as while configuring the workers.properties.

<Connector protocol="AJP/1.3" port="8009" address="${jboss.bind.address}" redirectPort="8443" />

Configure the other node(s) accordingly.

Next, Start Apache httpd and the Jboss/tomcat node(s) that you  have configured.