Tomcat clustering

Question

can anybody help me to set up a simple cluster for web services in red hat. i prefer tomcat version 5 or later. thanks.

Answer 1

Below are the steps I took to set up an Apache/Tomcat cluster. Tomcat 5 comes witha balencer web app that you can you use if you don't want to use apache (see tomcat documentation) but the balencer does a HTTP redirect that may not be suitable for all applications (eg webservices)
1: Install two instances of tomcat.
2: Configure the tomcat instances to listen on seperate ports (if running on same host machine)
server.xml : <Server port="9006" shutdown="SHUTDOWN" debug="0">
3: Enable session replication by uncommenting the cluster section of the server.xml file
(tcpListenPort should be different for each tomcat instance if running on same host machine)
<Cluster className="org.apache.catalina.cluster.tcp.SimpleTcpCluster"
managerClassName="org.apache.catalina.cluster.session.DeltaManager"
expireSessionsOnShutdown="true"
useDirtyFlag="true">
<Membership
className="org.apache.catalina.cluster.mcast.McastService"
mcastAddr="228.0.0.4"
mcastPort="45564"
mcastFrequency="500"
mcastDropTime="3000"/>
<Receiver
className="org.apache.catalina.cluster.tcp.ReplicationListener"
tcpListenAddress="127.0.0.1"
tcpListenPort="4002"
tcpSelectorTimeout="100"
tcpThreadCount="6"/>
<Sender
className="org.apache.catalina.cluster.tcp.ReplicationTransmitter"
replicationMode="pooled"/>
<Valve className="org.apache.catalina.cluster.tcp.ReplicationValve"
filter=".*\.gif;.*\.js;.*\.jpg;.*\.htm;.*\.html;.*\.txt;"/>
</Cluster>
4: Install an instance of Apache 2.0 webserver
     http://httpd.apache.org/download.cgi
5: DOwnload and install the mod_jk binaries for the OS that Apache 2.0 is installed on.
(Using mod_jk_1.2.6_2.0.50.dll on Windows)
     http://mirrors.combose.com/apache/jakarta/tomcat-connectors/jk/binaries/
6: Install the mod_jk binary by placing the mod_jk.dll or mod_jk.so file in {Apache install}/modules directory.
(re-name file if neccessary)
7: Edit the {Apache install}/conf/httpd.conf file to load the mod_jk module.
Windows example:
     # Load mod_jk module
     # Update this path to match your modules location
     LoadModule jk_module modules/mod_jk.dll <-- matches name in step 6
     # Declare the module for <IfModule directive>
     #AddModule mod_jk.c
     # Where to find workers.properties
     # Update this path to match your conf directory location (put workers.properties next to httpd.conf)
     JkWorkersFile {Apache install}/conf/workers.properties
     # Where to put jk logs
     # Update this path to match your logs directory location (put mod_jk.log next to access_log)
     JkLogFile {Apache install}/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 indicate to send SSL KEY SIZE,
     #JkOptions ForwardKeySize ForwardURICompat -ForwardDirectories
     # JkRequestLogFormat set the request format
     JkRequestLogFormat "%w %V %T"
     # Send everything for context /examples to worker named worker1 (ajp13)
     JkMount /examples/* loadbalancer <-- application to load/see workers.properties for loadbalancer
     JkMount /olp/* loadbalancer
8: Create a {Apache install}/conf/worker.properties file
     # Define workers using ajp13
     worker.list=worker1,worker2,loadbalancer
     # Set properties for loadbalancer (ajp13)
     worker.loadbalancer.type=lb
     worker.loadbalancer.balanced_workers=worker1,worker2
     worker.loadbalancer.sticky_session=false
     # Set properties for worker1 (ajp13)
     worker.worker1.type=ajp13
     worker.worker1.host=localhost
     worker.worker1.port=9009 <-- port must match value set in step 9
     worker.worker1.lbfactor=50 <-- Controls how requests are allocated
     worker.worker1.cachesize=10
     worker.worker1.cache_timeout=600
     worker.worker1.socket_keepalive=1
     worker.worker1.reclycle_timeout=300
     # Set properties for worker2 (ajp13)
     worker.worker2.type=ajp13
     worker.worker2.host=localhost
     worker.worker2.port=10009 <-- port must match value set in step 9
     worker.worker2.lbfactor=50 <-- Controls how requests are allocated
     worker.worker2.cachesize=10
     worker.worker2.cache_timeout=600
     worker.worker2.socket_keepalive=1
     worker.worker2.reclycle_timeout=300
9: Enable ajp13 connections in tomcat by uncommenting the Coyote/JK2 AJP 1.3 section of conf/sever.xml.
The port value must match the port value set in the Apache workers.properties file.
(if both instances of tomcat are running on the same host then the ports need to be different)
     <!-- Define a Coyote/JK2 AJP 1.3 Connector on port 8009 -->
     <Connector port="8010"
enableLookups="false" redirectPort="8443" debug="0"
protocol="AJP/1.3" />
RESOURCES :
http://raibledesigns.com/tomcat/
http://www.javaworld.com/javaworld/jw-12-2004/jw-1220-tomcat.html
NOTE : The tomcat balancer web app works by setting the HTTP re-direct META-TAG. This doesn't work for
SOAP based RPC calls. Also does not allow for "sticky session" routing, only "round robin" routing.
The mod_jk performs "round robin" routing by default. A combination "round robin"/"sticky session"
routing can be enabled by setting worker.loadbalancer.sticky_session=true.