Monitoring the Performance of Your Tomcat Application Server Using JavaMelody

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Javamelody is an opensource (LGPL) application to monitor Java or Java EE application servers in QA and production environments.

JavaMelody is mainly based on statistics of requests and on evolution charts.

(Extract from the Javamelody home page)

It allows to improve applications in QA and production
Give facts about the average response times and number of executions
Make decisions when trends are bad, before problems become too serious
Optimize based on the more limiting response times
Find the root causes of response times
Verify the real improvement after optimization

It includes summary charts showing the evolution over time of the following indicators:

Number of executions, mean execution times and percentage of errors of http requests, sql requests, jsp pages or methods of business façades (if EJB3, Spring or Guice)
Java memory
Java CPU
Number of user sessions
Number of jdbc connections

These charts can be viewed on the current day, week, month, year or custom period.
You can even execute garbage collection to free resources, or view / invalidate http sessions.

Setting up Javamelody on your server

*Step 1: *
Download the javamelody-1.36.0.zip zip file.
Now, unzip, and add copy the files javamelody.jar and jrobin-x.jar into the in the lib directory of Tomcat.

*Step 2: *
Add the following lines in the web.xml file of the conf directory of Tomcat (and not in the WEB-INF/web.xml files of the webapps).

web.xml.snippet

        <filter>
                <filter-name>monitoring</filter-name>
                <filter-class>net.bull.javamelody.MonitoringFilter</filter-class>
        </filter>
        <filter-mapping>
                <filter-name>monitoring</filter-name>
                <url-pattern>/*</url-pattern>
        </filter-mapping>
        <listener>
                <listener-class>net.bull.javamelody.SessionListener</listener-class>
        </listener>

Once this is done, all you need to do is restart the application. Once the application is up, navigate to http://<host>/<context>/monitoring url to view a whole set of interesting data.

The full instrcutions are available here.

What does the Javamelody monitoring page look like?

Attached below is a screenshot of my Javamelody monitoring page. Note that this screenshot is of a development environment with no data and just a single user.

Disclaimer : I was only able to try out Javamelody on a development environment. Therefore, implementers are advised to test out Javamelody on a trial environment before moving it into the production server/s.