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Lambda Probe Essentials: The Top 5 Features for Tomcat Administration

Get to know Lambda Probe, an open source tool for effective and comprehensive monitoring and administration of the Tomcat application server.

pache Tomcat probably is the most popular open source web application server on the planet. The one thing it is designed to do—run Java-based web applications—it does extremely well. Not only is it simple to run and administer, but it is reliable, robust, and high performing as well.

For performance management and monitoring, Tomcat usually provides access to all the essential information through performance logs and JMX (Java Management Extensions) beans, which are hard to read and interpret. In my operations with Tomcat I often need to access essential information about runtime performance in a more uniform and easy-to-understand fashion. That is how I came across Lambda Probe, an excellent open source tool for Tomcat system administrators to perform runtime monitoring and inspections.

Lambda Probe is a beautifully designed, web-based performance-monitoring tool that provides easy and intuitive access to all runtime parameters, as well as the ability to run predictability tests on the Tomcat runtime. This article explores the most essential features of Lambda Probe and explains what it takes to install and configure this handy tool.

Lambda Probe Installation
Because Lambda Probe essentially is a Java web application archive (WAR) distributed as a zip file, installing it on the Tomcat application server is quite simple. You can install it either through Tomcat's manager application or by simply extracting the zip application into the Tomcat's webapps directory as follows:

cd $CATALINA_HOME/webapps
unzip probe1.7b  

To enable web access to Lambda Probe, you need to alter Tomcat's tomcat-user.xml file and add the following four roles to it:

  • manager—This role has full access to Lambda Probe functionality. (It is already defined.)
  • poweruser—This role has the same privileges as manager except the ability to deploy and remove applications and monitor Tomcat via "quick check."
  • poweruserplus—This role has the same privileges as poweruser plus the ability to restart the Java Virtual Machine.
  • probeuser—This is the least-privileged Lambda Probe role; it is restricted to read-only functionality.

Here is the code to define all four roles:

<?xml version='1.0' encoding='utf-8'?>
  <role rolename="manager"/>
  <role rolename="tomcat"/>
  <role rolename="poweruser"/>
  <role rolename="role1"/>
  <role rolename="poweruserplus"/>
  <role rolename="probeuser"/>
  <user username="both" password="tomcat" roles="tomcat,role1"/>
  <user username="tomcat" password="tomcat" roles="tomcat,manager,poweruser,poweruserplus,probeuser"/>
  <user username="role1" password="tomcat" roles="role1"/>

After all the roles are defined, go to Tomcat's bin directory and restart Tomcat:


After the server is up, navigate to the Lambda Probe application URL:


This URL assumes you are trying this on a localhost, port 8080.

To complete the installation, supply the username and password of each user in the four Lambda Probe user roles.

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