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;