Chapter 24. jmx (optional)

24.1. jmx (optional): JMX Management of Performance Monitor

24.2. Introduction

In this lab you will use JMX to monitor a running application remotely. You will use the RepositoryPerformanceMonitor to collect performance metrics and expose them via JMX.

Specific subjects you will gain experience with:

  1. How to expose a Spring bean as a JMX MBean
  2. How to control the management interface of the exposed JMX MBean
  3. How to export pre-existing MBeans

What you will learn:

  1. @ManagedResource, @ManagedAttribute, @ManagedOperation
  2. @EnableMBeanExport

Estimated time to complete: 30 mins

24.3. Quick Instructions

Quick instructions for this exercise have been embedded within the lab materials in the form of TODO comments. To display them, open the Tasks view (Window >> Show View >> Tasks (not Task List)).

24.4. Detailed Instructions

24.4.1. Exposing the MonitorFactory via JMX

24.4.1.1. Check the Application Runs>

(TODO 01) This is already a complete, working application. Run it now by right-clicking on the project and selecting Run As …​ > Run Spring Boot App. Open a browser window to http://localhost:8080 to see the usual home page.

Once you are happy the application is working, you can stop it so we can modify the code.

24.4.1.2. Assess the initial state of the JamonMonitorFactory

Find and open the JamonMonitorFactory class in the rewards.internal.monitor.jamon package. Notice that this is an implementation of the MonitorFactory interface that uses the JAMon library to accomplish it’s performance monitoring.

When you are comfortable with the implementation of this class, move on to the next step where you export an instance of this bean via JMX

24.4.1.3. Add JMX metadata to the implementation class

(TODO 02) Add Spring’s JMX annotations @ManagedResource, @ManagedAttribute and @ManagedOperation to the class as well as methods you want to expose via JMX. Use statistics:name=monitorFactory as name for the bean exposed.

By placing the data collection and exposure of performance metrics in the JamonMonitorFactory class, we’ve ensured that the RepositoryMonitorFactory is completely decoupled from any reporting mechanism. The MonitorFactory interface is very generic, but allows each implementation strategy to expose any data it sees fit.

When you have finished exporting the JamonMonitorFactory class to JMX, move on the next step

24.4.1.4. Activate annotation driven JMX in application configuration

(TODO 03) Find and open the AspectsConfig class in the config package. In this file activate annotation driven JMX by adding the appropriate annotation.

24.4.1.5. Start the MBeanServer and deploy the web application

In this step, you will deploy the project as a Spring Boot application. However, before you can do that, you must tell the Java VM to start an MBeanServer.

IMPORTANT STEP: (TODO 04) To start our MBeanServer, open the Window menu, go to "Preferences…​", then select "Java > Installed JREs" on the left. Select "Edit…​" for the JRE that you are using and add -Dcom.sun.management.jmxremote as a VM argument. This value instructs the JVM to start the internal MBeanServer and also allows connections to it via shared memory, so that when you run JConsole it will see the process and allow you to directly connect to it, instead of needing to use a socket connection, with a name/password required.

(TODO 05) Now deploy the project as a web application. Once deployed, open http://localhost:8080 in your browser. You should see the welcome page display containing a link to submit a new reward.

24.4.1.6. View the monitor statistics using JConsole

(TODO 06) From the command line of your system, or Windows Explorer, run the $JDK_HOME/bin/JConsole application. When this application starts up, choose the process that identifies your web application and open it.

[Tip] Tip

If you can not see the process you started, in JConsole, it is possible you do not have adequate security rights in your environment. In this case, you will have to connect to the process via a socket connection instead. In the VM arguments tab of your launch configuration, add the following arguments:

   -Dcom.sun.management.jmxremote.port=8181
   -Dcom.sun.management.jmxremote.authenticate=false
   -Dcom.sun.management.jmxremote.ssl=false

Then restart the process, and connect via JConsole by using the 'Remote' tab, specifying a host of localhost and port of 8181.

Once connected to the application, navigate to the MBeans tab and find the MBean you exported.

monitor factory mbean

Figure 24.1. The MonitorFactory MBean



Once you have found the MBean, execute a few rewards operations in the browser and refresh the MBean attributes. You should see something similar to this

monitor factory attributes 2

Figure 24.2. The MonitorFactory attributes



[Note] Note

Double clicking on any scalar value will create a graph over time

scalar value graph

Figure 24.3. Scalar value graph

Explore the attributes and operations of the MBean and when you are finished move to the next section

24.4.2. Spring Boot MBeans

Spring Boot applications export a predefined MBean that gives you the ability, via JMX to monitor and interact with your application (it offers similar functionality to the Actuator endpoints).

In JConsole you should see the "org.springframework.boot" MBean. Open it up and explore what you find. For example, you should be able to

  • Query the value of properties set in application.properties
  • Get a list of Spring beans
  • View the URL mappings of the Controllers

Once you have completed this step, you have completed the lab.

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