Monitoring Java Application Servers with check_jmx in Nagios XI

JMX (Java Management Extensions) is a technology in Java that allows developers to monitor and manage applications, system objects, devices, and services. It provides a standard way to access runtime data and control Java applications.

JMX is commonly used for:

• Monitoring memory usage, CPU load, thread count, and garbage collection.
• Managing application settings dynamically.
• Exposing application metrics for external monitoring tools like Nagios, Prometheus, and Grafana.

Prerequisites

Before proceeding, ensure you have the following:

• A remote server running JMX.
• A Nagios XI server with network connectivity to the JMX server.
• The NRPE agent installed on the remote server.

Editing Files

Throughout this guide, you will need to edit configuration files. This guide uses the vi text editor:

• Press i to enter insert mode.
• Press Esc to exit insert mode.
• Save and exit by typing :wq and pressing Enter.

check_jmx Plugin Overview

The check_jmx plugin, available at GitHub, provides monitoring for:

• Standard Java JMX parameters (memory, threads, OS, garbage collection)
• Tomcat metrics (requests, processing time, threads)
• Spring framework Java beans
• JBoss objects and beans

Installing the Plugin

To install check_jmx, execute the following commands on your JMX server:

cd /usr/local/nagios/libexec/
wget -O check_jmx "https://raw.githubusercontent.com/WillPlatnick/jmxquery/master/plugin/check_jmx"
wget -O jmxquery.jar "https://github.com/WillPlatnick/jmxquery/raw/master/plugin/jmxquery.jar"
chmod +x *jmx*
chown nagios:nagios *jmx*

Testing the Plugin

Run the following command to test check_jmx:

./check_jmx -U service:jmx:rmi:///jndi/rmi://localhost:<port>/jmxrmi -O java.lang:type=Memory -A HeapMemoryUsage -K used -I HeapMemoryUsage -J used -vvvv -w 4248302272 -c 5498760192

Expected output:

JMX OK - HeapMemoryUsage.used=79112000 | HeapMemoryUsage.used=79112000,committed=954204160;init=964689920;max=954204160;used=79112000

Replace <port> with the correct JMX application port (e.g., 7199 in future steps).

Configuring NRPE

To allow Nagios XI to execute check_jmx, define the command in nrpe.cfg on the JMX server:

vi /usr/local/nagios/etc/nrpe.cfg

Add the following line:

command[check_jmx]=/usr/local/nagios/libexec/check_jmx $ARG1$

Restart the NRPE service:

service xinetd restart

Testing from Nagios XI Server

Execute the following command from the Nagios XI server, replacing <jmx_server_ip>:

/usr/local/nagios/libexec/check_nrpe -H <jmx_server_ip> -c check_jmx -a '-U service:jmx:rmi:///jndi/rmi://127.0.0.1:7199/jmxrmi -O java.lang:type=Memory -A HeapMemoryUsage -K used -I HeapMemoryUsage -J used -vvvv -w 4248302272 -c 5498760192'

Expected output:

JMX OK - HeapMemoryUsage.used=94443776 | HeapMemoryUsage.used=94443776,committed=954204160;init=964689920;max=954204160;used=94443776

Creating Nagios Monitoring Objects

Use the NRPE Configuration Wizard to create monitoring objects:

1. Navigate to Run a Wizard.
2. Select NRPE wizard.

3. Enter the JMX server’s IP and select CentOS as the OS.
4. Click Next and configure the monitoring parameters.
5. Define the command for check_jmx in the Command Args field:

'-U service:jmx:rmi:///jndi/rmi://127.0.0.1:7199/jmxrmi -O java.lang:type=Memory -A HeapMemoryUsage -K used -I HeapMemoryUsage -J used -vvvv -w 4248302272 -c 5498760192'

6. Click Next and complete the wizard steps.
7. Click Finish to create and apply the monitoring configuration.
8. Click View status details to verify monitoring.

Using check_jmx With Authentication

For authenticated JMX servers, include -username and -password arguments:

/usr/local/nagios/libexec/check_nrpe -H <jmx_server_ip> -c check_jmx -a '-U service:jmx:rmi:///jndi/rmi://127.0.0.1:7199/jmxrmi -O java.lang:type=Memory -A HeapMemoryUsage -K used -I HeapMemoryUsage -J used -vvvv -w 4248302272 -c 5498760192 -username admin -password welcome123'

Additional check_jmx Configurations

• Garbage Collection:

-U service:jmx:rmi:///jndi/rmi://127.0.0.1:7199/jmxrmi -O java.lang:type=GarbageCollector,name=ConcurrentMarkSweep -A LastGcInfo -K duration -u ms -vvvv -w xxx -c yyy

• Thread Count:

-U service:jmx:rmi:///jndi/rmi://127.0.0.1:7199/jmxrmi -O java.lang:type=Threading -A ThreadCount -w xxx -c yyy

• System Load:

A:type=OperatingSystem -A SystemLoadAverage -w xxx -c yyy

Adding Additional Services

You can add additional checks by:

• Running the NRPE Wizard again.
• Copying an existing service:
  1. Navigate to Configure > Core Configuration Manager > Monitoring > Services.
  2. Click Copy on an existing service.
  3. Click Modify on the copied service.
  4. Change the Description to reflect the new check (e.g., “Thread Count”).
  5. Update the $ARG2$ field:

-a '-U service:jmx:rmi:///jndi/rmi://127.0.0.1:7199/jmxrmi -O java.lang:type=Threading -A ThreadCount -w 250 -c 500'

6. Ensure the Active checkbox is checked.
7. Click Save and Apply Configuration.

Once applied, the new service will be monitored in Nagios XI.