Use Jolokia to monitor JMX endpoint of webapp on same Tomcat server

Question

Jolokia is uncharted territory for me, and after having read the documentation, I'm still not sure if it'll work with the scenario I have in mind.

Setup:

• Tomcat application server (version ranges from 6.x to 7.x), usually on a Windows platform, occasionally a flavour of Linux.
• Deployed third-party Java web application (SAP BusinessObjects) with JMX monitoring enabled (accessible through RMI).

Possible gotcha's:

• The Java web application to be monitored is commercial and closed source, so modifications are not possible. The only thing that can be changed is the JMX port number
• The JMX endpoint is a custom one, thus not the default jmxrmi endpoint.
• The JMX connection requires authentication.

Goal:

What I'd like to do is to deploy the Jolokia WAR file onto the Tomcat server and then configure it so that I can read the MBean attributes from the other web application.

I would code the client myself using Python (version 3) and the Requests HTTP library.

I've been reading through the Jolokia documentation (again, I'm a complete newbie at this point), but can't figure out if this would be possible or not (as I can't seem to find where to enter the JMX/RMI url or the authentication information).

Questions:

1. Can I use the WAR agent for this setup?
2. If not, can you please explain why (so I can understand, not because I don't believe you). Also, is there another agent that's more suited for this scenario?
3. If yes, can you point me in the right direction how to configure the Jolokia to the web application to connect to?

Answer 1

First of all, Jolokia by passes the JSR-160 connector stuff completely, so there is no need for any JMX/RMI authentication. The whole purpose of Jolokia is to provide a bridge over HTTP/JSON to the internal JMX subsystem. Depending on the agent, you can secure Jolokia quite easily. For the WAR agent, securing is the same as for any Java EE web app: Setup some roles and users for tomcat (e.g. in tomcat-users.xml) and reference the role in the security contstraints within the jolokia.war's /WEB-INF/web.xml.

To your questions:

1. Yes, you can. If you don't have any specific authentication needs, simply drop the jolokia.war into tomcat's /webapps directory. I suggest to try this first before adding security. For deinstalling the agent, simply remove the war.

2. As an alternative, you could also use the JVM agent, which opens an own HTTP server on an extra port (default: 8778). More on this in the reference manual

3. There is no need for a dedicated connection to the web app since MBeans are registered globally and are accesible from anywhere in the JVM. A webapp should of course select carefully the management information it exposes. So, there is no extra step needed and you can access the MBeans for the WEB app directly (except when it does something unusual with Java security, but I don't think so).

To test the installation, simply connect to the Tomcat with your browser and the context /jolokia (e.g. "http://localhost:8080/jolokia"). You should see the version information about the agent itself.

The next step would be to explore the JMX namespace, either with the browser (and operation "list" like in http://localhost:8080/jolokia/list , but that's tedious) or with a client like j4psh or hawt.io. Hopefully you will find the MBeans of your webapp you are looking for.