Run multiple tomcat instances on one machine

In this post, I am going to explain, how to run multiple tomcat instances on one machine.

We can create multiple instances in two ways.

         a. By sharing the same tomcat code base across all instances

         b. By creating separate copies of tomcat images

To work with multiple instances of tomcat, we need to play with configuration files, First will understand basic directory structure of tomcat.

Directory	Description
bin	Contains all startup, shoutdown scripts
conf	Contains tomcat configuration files. server.xml, web.xml are mainly used.
lib	Contains all the necessary jars that tomcat require.
logs	Directory contains tomcat log files
webapps	Web applications are deployed in this directory
work	Tomcat place all servlets that are generated from JSPs.

Following are the port details, that you need to know while configuring multiple instances of the same server installation.

Port	Description
Connector port	Tomcat listen http requests on this port
Shutdown port	This port is used while shutting down tomcat
AJP (Apache JServ Protocol) Connector Port	The AJP Connector element represents a Connector component that communicates with a web connector via the AJP protocol.
Redirect Port	All the redirection operations will happen through this port.

Following procedure explains how to configure multiple instances of tomcat.

Step 1: Download Apache tomcat. Copy the same image to some other folder.

$ ls apache-tomcat-8*
apache-tomcat-8.0.22:
AuditViolations.html	LICENSE			RELEASE-NOTES		bin			lib			temp			work
AuditViolations_files	NOTICE			RUNNING.txt		conf			logs			webapps

apache-tomcat-8.0.22_image1:
AuditViolations.html	LICENSE			RELEASE-NOTES		bin			lib			temp			work
AuditViolations_files	NOTICE			RUNNING.txt		conf			logs			webapps

In this example, I am using two images of tomcat apache-tomcat-8.0.22, apache-tomcat-8.0.22_image1.

Step 2: Open server.xml (apache-tomcat-8.0.22_image1/conf/server.xml) file of apache-tomcat-8.0.22_image1 and change the HTTP, HTTPS, AJP, Shutdown Ports.

Step 3: Update catalina.sh file in both tomcat instances.

Add following variables to apache-tomcat-8.0.22/bin/catalina.sh

export CATALINA_HOME= /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22

export CATALINA_BASE= /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22

Add following variables to apache-tomcat-8.0.22_image1/bin/catalina.sh

export CATALINA_HOME= /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22_image1

export CATALINA_BASE= /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22_image1

Go to bin directories of tomcat run startup.sh scripts.

$ ./startup.sh
/Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22/bin/catalina.sh: line 98: export: `/Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22': not a valid identifier
/Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22/bin/catalina.sh: line 99: export: `/Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22': not a valid identifier
Using CATALINA_BASE:   /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22
Using CATALINA_HOME:   /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22
Using CATALINA_TMPDIR: /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22/temp
Using JRE_HOME:        /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home
Using CLASSPATH:       /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22/bin/bootstrap.jar:/Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22/bin/tomcat-juli.jar
Tomcat started.

$ ./startup.sh 
/Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22_image1/bin/catalina.sh: line 98: export: `/Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22_image1': not a valid identifier
/Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22_image1/bin/catalina.sh: line 99: export: `/Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22_image1': not a valid identifier
Using CATALINA_BASE:   /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22_image1
Using CATALINA_HOME:   /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22_image1
Using CATALINA_TMPDIR: /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22_image1/temp
Using JRE_HOME:        /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home
Using CLASSPATH:       /Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22_image1/bin/bootstrap.jar:/Users/harikrishna_gurram/softwares/apache-tomcat-8.0.22_image1/bin/tomcat-juli.jar
Tomcat started.

Open browser and hit the URLs http://localhost:8080, http://localhost:8081. You will get following screen.

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