This is a Nagios/Shinken plugin that allows the easy monitoring of Java applications through Java's JMX interface.

check_java will connect to a Java application and check one type of property per run against user-defined limits. This is governed by command line parameters to check_java, it is called like this:

check_java [-u URL] -t TYPE -w WARN -c CRIT

The meaning of the parameters is as follows:

-u URL: The JMX service URL check_java will connect to. For details on how the
        URL is constructed see the section "URL". If no URL is given, a default
        URL is used:
           service:jmx:rmi:///jndi/rmi://:9000/jmxrmi

-t TYPE: The property type to check. See the Section "Types" for more
         information about the available types.

-w WARN: The warning threshold. If a property value is greater than this number,
         check_java will return a WARNING state to Nagios.

-c CRIT: The critical threshold. If a property value is greater than this number,
         check_java will return a CRITICAL state to Nagios.

You can turn any Java application into a JMX server (aka JMX agent) by supplying some additional parameters to the JVM. Call your JMX application like this:

java \
-Dcom.sun.management.jmxremote \
-Dcom.sun.management.jmxremote.authenticate=false \
-Dcom.sun.management.jmxremote.ssl=false \
-Dcom.sun.management.jmxremote.port=9000 \
-Djava.rmi.server.hostname=localhost \

This will start a JMX agent on the loopback interface that listens for incoming connections on port 9000. Authentication and SSL are turned off as they are currently unsupported by check_java. In case your application is also using RMI, you should probably drop the last parameter so no hostname and thus interface is set. Most applications will take care of this automatically, so you should not interfere. In this case, you should be extra careful not to expose the JMX port to the whole world, as anyone could just connect and use JMX to potentially even control your JVM.

After you have started your JMX agent, you need to tell check_java how it can connect to that agent. This is done through the URL parameter -u. JMX agent URLs are constructed in the following manner:

service:jmx:rmi:///jndi/rmi://<TARGET_MACHINE>:<RMI_REGISTRY_PORT>/jmxrmi

<TARGET_MACHINE> is the IP address (or resolvable name) of the machine you want to connect to, normally the same as the java.rmi.server.hostname property you set when starting the agent. the <RMI_REGISTRY_PORT> is the port number set using the com.sun.management.jmxremote.port property you set when starting the agent.

If the URL parameter -u is not given on the command line, check_java uses the default URL service:jmx:rmi:///jndi/rmi://:9000/jmxrmi. Using this URL, check_java will connect to a JMX agent on localhost at port 9000.

check_java is able to check several standard JMX attributes provided by the JVM itself, thus independent of the actually running program. Currently it is not possible to check arbitrary JMX attributes.

A check can be invoked by giving the check name to the check_java type parameter -t.

This check will return the amount of used heap memory. In the performance data fields, also the values for the initial allocation size of the heap memory, the current allocation of the heap memory, and the maximum allowed heap memory allocation are returned.

This check will return the amount of used non-heap memory. In the performance data fields, also the values for the initial allocation size of the non-heap memory, the current allocation of the heap memory, and the maximum allowed heap memory allocation are returned.

This check will return the amount of used memory in the memory pool Eden. In the performance data fiels, the values for the initial size of the memory pool, the current size of the memory pool, and the current maximum size of the memory pool are returned.

This check will return the amount of used memory in the memory pool Survivor. In the performance data fiels, the values for the initial size of the memory pool, the current size of the memory pool, and the current maximum size of the memory pool are returned.

This check will return the amount of used memory in the memory pool Code Cache. In the performance data fiels, the values for the initial size of the memory pool, the current size of the memory pool, and the current maximum size of the memory pool are returned.

This check will return the number of runs of the Mark and Sweep Garbage Collector. This is currently an experimental feature and not yet thoroughly tested.

This check will return the amount of time consumed by the Mark and Sweep Garbage Collector. This is currently an experimental feature and not yet thoroughly tested.

This check will return the number of currently loaded classes. In the performance data fields, the number of total loaded classed, and the number of unloaded classes are returned as well.

This check will return the number of currently existing threads. In the performance data fields, the number of total started threads, and the number of currently existing daemon threads are returned as well.

Copyright (c) 2015, Sebastian Schäfer [email protected] All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
• Neither the name of check_java nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

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