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Tomcat - Basic Clustering

Tomcat - Basic Clustering

  • Till now we have 1 tomcat instance running and now we'll learn how to loadbalance multiple tomcat instances.
  • For this let us have another tomcat instance configured first.
  • Go to the /opt directory and copy tomcat8 to tomcat8-n2
# cp -prv tomcat8 tomcat8-n2
  • Now we know that we are using some ports for tomcat say 8080, 8005, 8009
  • For our additional tomcat instance we need to change the ports. If we don't then we might need to experience port conflict
  • I am going to edit server.xml config file in the new node and increment the port numbers by 1
# cd /opt/tomcat8-n2/conf/
# vi server.xml

8005 -> 8006
8080 -> 8081
8443 -> 8444
8009 -> 8010
  • Now you need to add your new Catalina home, base and temp directories
  • First you need to change the catalina.sh script and redirect the above 3 variables to the new variables
  • Edit the catalina.sh script and add the following lines
# vi /opt/tomcat-n2/bin/catalina.sh

CATALINA_BASE=$CATALINA_BASE2
CATALINA_HOME=$CATALINA_HOME2
CATALINA_TMPDIR=$CATALINA_TMPDIR2
  • Now edit /etc/profile file and set our new directories
# vi /etc/profile

CATALINA_BASE2=/opt/tomcat8-n2
CATALINA_HOME2=/opt/tomcat8-n2
CATALINA_TMPDIR2=/opt/tomcat8-n2/temp
  • Now we need to edit /etc/nginx/vhost.d/default.conf file to add the upstream directive to loadbalance
  • Edit that file and add the following at the top of the file
upstream myTomcat {
 server localhost:8080;
 server localhost:8081;
}
  • Now we need to change the proxy_pass
proxy_pass http://myTomcat;

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