check_jmx4perl

'check_jmx4perl' is a Nagios Plugin for accessing JMX attributes. It uses an agent based approach where the plugin accesses a special servlet deployed on the JEE Server to monitor. This agent (and agents for other platforms) is provided by Jolokia (http://www.jolokia.org)

Benefits of this approach compared to the traditional way of accessing JMX remotely via JSR 160 connectors are:

* No Java installation required on the Nagios host
* Fast plugin startup times because no JVM needs to be launched.
* No special JEE Server startup options required in order to access JMX information remotely
* JSON serialization allows deep access into Java objects
* Firewall friendly communication via HTTP

However, jmx4perl can be operated in a proxy mode where a dedicated proxy server accesses the target platform via JSR-160 JMX remoting. This allows for an agentless operation without the need of installing any extra software on the target server.

Beside this technical advantages, check_jmx4perl provides also a rich feature set:

* Access to JMX attributes and return values of JMX operations for monitoring purposes
* Incremental mode for monitoring the velocity of value changes, e.g. the growth rate of the thread count
* Relative monitoring of values by providing a base value attribute, e.g. for checking that the memory used is below 80% of the available memory
* Deep access to arbitrary Java bean attributes, e.g. the statistics values of a JSR77 Stats object
* Alias names for common attributes and operations
* Selective access to a predefined set of MBeans by providing an access policy file to the agent servlet

This plugin has been tested on a multitude of JEE Servers (JBoss, Oracle Weblogic, IBM Websphere, Glassfish, Tomcat, Jetty and more). It will work on any Servlet Container running on at least Java 1.5.

'check_jmx4perl' is part of a larger distribution, jmx4perl. In addition to this Nagios plugin, jmx4perl contains tools for exploring and examing the available JMX MBeans on the JEE-Server so that it is easy to discover the MBeans and attributes worth monitoring.