Attributes

JVM Configuration

Each JVM that will be monitored must be configured to allow access to the JMX server that runs inside of each monitored JVM. Configuration is accomplished by providing a few system parameters to the JVM upon application startup. The parameters are listed below along with their description.

Example:

/java -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=3306 -Dcom.sun.management.jmxremote.authenticate=false

Use netstat prior to starting or restarting your application to ensure that the configured port is not in use. Restart your Java application using the new configuration. Then run netstat again to ensure that the system reports a listening port on the selected configuration port.

JMX Discovery

JConsole is a JVM monitoring application that has been in existence since the release of Java JDK 1.5.x. With JConsole it is possible to explore all JMX managed beans in a virtual machine once the JVM is configured to allow JMX remote access as described above. The JConsole executable can be found in the bin directory for your JDK1.5.x or greater installation.

Launch JConsole and select the “Remote Process” option button. Enter localhost:in the entry text box, where the port is the configured JMX listener port. Then select the “Connect” button.

Once started, JConsole will display several tabs. Select the “Mbeans” tab. Along the left hand side is a tree view that lists each deployed Mbean in the JMX Managed Bean Server. The treeview allows exploring down to each Mbean and displays each Mbean attribute or operation. Once you have navigated down to the bean level JConsole will display the Mbean name in the display on the right hand side.

Individual JMX Attribute Access

FireScope makes available a client access tool called jmxdelegate for querying and setting individual Mbean attributes and invoking Mbean operations. As described above, the JConsole utility can be used to determine the names and attributes of Mbeans deployed in a particular java virtual machine. The bean names, attributes names and operation names are passed to the jmxdelegate tool for access.

First deploy the jmxdelegate.jar file to an appropriate location on your monitored system. The following example uses a bean names from a system that has a default Tomcat version 6.0.13 deployed running and configured for JMX access.

The jmxclient tool uses the following command format:

/java -Dhost= -Dport= -DbeanName= -Dattribute= -Dparameters= -DnestedResult= -jar /jmxdelegate.jar

The following example command line will retrieve the requestCount? Attribute from the deployed tomcat manager application that comes as a part of the standard Tomcat deployment:

/java -Dhost=localhost -Dport=3306 -DbeanName=Catalina:j2eeType=Servlet,name=HTMLManager,WebModule=//localhost/manager,J2EEApplication=none,J2EEServer=none -Dattribute=requestCount -jar jmxdelegate.jar

Note the nested / complex bean name created by Tomcat shown again as follows:

Catalina:j2eeType=Servlet,name=HTMLManager,WebModule=//localhost/manager,J2EEApplication=none,J2EEServer=none

Invoking the above command returns the current requestCount.

Now invoke the manager via a web browser as follows: http://localhost:8080/manager/html

Then re-invoke jmxclient tool to show that the request count increases with each manager invocation.

Example of FireScope JMX Managed Beans

The FireScope solution is delivered with an application called SyslogListener. The SyslogListener application receives syslog messages over TCP/IP and transfers these messages to the FireScope database. The SyslogListener application contains a few managed beans which expose some data points which may be of interest to FireScope users. The exposed beans are described in the following table:

Accessing the FireScope managed beans can be accomplished via the following jmxclient invocations:

/java -Dhost=localhost -Dport=3306 -DbeanName=com.firescope.sysloglistener:name=ReceiveMessageCount -Dattribute=PerMinuteMessageCount -jar jmxdelegate.jar

/java -Dhost=localhost -Dport=3306 -DbeanName=com.firescope.sysloglistener:name=ReceiveMessageCount -Dattribute=DailyMessageCount -jar jmxdelegate.jar

/java -Dhost=localhost -Dport=3306 -DbeanName=com.firescope.sysloglistener:name=PersistedMessageCount -Dattribute=PerMinuteMessageCount -jar jmxdelegate.jar

/java -Dhost=localhost -Dport=3306 -DbeanName=com.firescope.sysloglistener:name=PersistedMessageCount -Dattribute=DailyMessageCount -jar jmxdelegate.jar

/java -Dhost=localhost -Dport=3306 -DbeanName=com.firescope.sysloglistener:name=MessageExecutionTime -Dattribute=DurationMilliSeconds -jar jmxdelegate.jar

/java -Dhost=localhost -Dport=3306 -DbeanName=com.firescope.sysloglistener:name=DatabaseRefresher -Dattribute=ForceDatabaseRefresh -jar jmxdelegate.jar

FireScope JMX Agent Configuration

The following list outlines prerequisites for enabling FireScope JMX monitoring on remote hosts:

• A valid Java runtime (JRE) must be deployed and available on the remote host
• The jmxdelegate.jar file must be deployed and executable on the remote host.
• UserParameters must be defined and added to the agent configuration file on the remote host.
• The remote agent must be restarted
• It is recommended that the new UserParameter be tested on the remote host

For the purposes of this example we shall assume each of the following has been configured as described below:

• A Java VM has already been configured for JMX access on port 4900
• A Java executable exists in the path
• The jmxdelegate.jar file has been deployed to /jars directory
• Our new user parameter shall be called java.application.monitored.value
• Our JMX bean name is called application.MBean
• The property of interest on this Mbean is called property

To configure our new user parameter we edit the agent configuration file by adding the following line:

UserParameter=java.application.monitored.value,java -Dhost=localhost -Dport=4900 -DbeanName=application.MBean -Dattribute=property -jar /jars/jmxdelegate.jar

FireScope JMX Server Configuration

Create a Configuration Item (CI) that references the UserParameter that was created in the previous section. See Creating a Configuration Item.

JMX Enabling Your Own Java Applications

The code listed below describes the steps necessary to make your applications JMX capable. The process covered outlines only standard Mbeans. For more information regarding other typs of Mbeans such as MXBeans, or DynamicBeans refer to the JMX API documentation or Java tutorial.

For any class that you wish to make available to JMX you must write an Mbean interface that lists the available JMX methods. The Mbean interface name must have the same prefix name as the implementing class.

public interface ExecutionMessageCounterMBean {
    public long getPerMinuteMessageCount();
    public long getDailyMessageCount();
}

Then provide an implementation for the above interface such as the following package example:

import java.util.Calendar;

public class ExecutionMessageCounter implements ExecutionMessageCounterMBean 
{
    private int lastIndex;
    private long[] perMinuteMessageCount;
    
    public ExecutionMessageCounter()
    {
        super();
        
        lastIndex = 0;
        perMinuteMessageCount = new long[1440];
    }
    
    public long getPerMinuteMessageCount()
    {
        int perMinuteMessageCountIndex = getMinuteIndexNow();
        
        return perMinuteMessageCount[perMinuteMessageCountIndex];
    }
    
    public long getDailyMessageCount()
    {
        long dailyMessageCount = 0;
        
        for(long oneMinuteCount : perMinuteMessageCount) {
            dailyMessageCount += oneMinuteCount;
        }
        
        return dailyMessageCount;
    }
    
    private synchronized int getMinuteIndexNow()
    {
        Calendar calendar = Calendar.getInstance();
        int resultIndex = calendar.get(Calendar.HOUR_OF_DAY) * 60 + calendar.get(Calendar.MINUTE);
        
        return resultIndex;
    }
}

Now register your managed bean with the local Mbean server. Each bean must be registered using a unique name. For purposes of this example we shall use the domain of example and a name of MessageCounter as shown below:

ExecutionMessageCounter counter = new ExecutionMessageCounter();
MBeanServer mBeanServer = ManagementFactory.getPlatformMBeanServer();

try {
    ObjectName objectName = new ObjectName("example:name=MessageCounter");
    mBeanServer.registerMBean(counter, objectName);
} 
catch(Exception exception) 
{
    // Add appropriate exception handling
}