Tutorials : Soup-to-Nuts Application Management with JMX :

JMX-Tiered Architecture

Figure 1: The JMX Architecture

• Instrumentation Tier: This tier is used to prepare the manageable resources for JMX support. To accomplish this, you need to know whether a resource can be manageable through JMX. A resource is manageable through JMX if it meets the following criteria:
  • It must be developed in Java (or provides a Java wrapper)
  • It must be an application (Java class, a part of a Java class, a servlet, a JSP page, EJB, and so on), service, device, or user.
  • It must be instrumented through Managed Beans (MBeans), which means it's been written in Java code that conforms to the MBeans specification. This also specifies a notification mechanism that allows MBeans to generate and propagate notification events to components of other levels.
• Agent Tier: This tier is generally located on the same computer as the managed resources. A JMX agent represents the JMX solution to expose MBeans and control managed resources. This makes them available to remote management applications. The following components comprise a JMX agent:

  • An MBeanServer, which is a server used to register objects that are exposed to an agent's management operations.
  • A set of MBeans, used for representing the managed resources.
  • Agent services implemented as MBeans. For example, a timer service, a monitor service, an MLet service, a relation service, etc.
  • At least one protocol adaptor/connector—like an HTML Adaptor or an RMI connector.

  Agents are developed by writing Java code conforming to a JMX agent's specification.

• Manager Tier: This last tier facilitates application management in order to communicate with JMX agents. This tier also offers interfaces for implementing JMX managers and defines components/interfaces that operate on JMX agents.

Figure 2: The Manager/JMX Agent/Managed Resource Communication Flow

Creating a Standard MBean

1. An MBean cannot be an abstract class.
2. An MBean must have at least one public constructor.
3. An MBean must implement an interface that represents the MBean.
4. The MBean interface name must follow the correct naming convention: {MBean class name}MBean.
5. MBean attributes can be of type read/write.
6. Attributes may have any Java type, including array.
7. An attribute of type read must have a method of type get{attribute name} where the attribute name starts with an upper case letter.
8. An attribute of type write must have a method of type set{attribute name} where the attribute name starts with an upper case letter.
9. In the case of a boolean attribute, you can use a method of type is{attribute name} where the attribute name starts with an upper case letter.
10. Attributes names cannot be overloaded.
11. Methods that do not represent attributes are known and exposed as operations.

• startProcess (*): This operation starts the process
• stopProcess (*): This operation stops the process
• haltProcess (*): This operation sets stand by on/off, low power, and restarts the process
• destroyProcess: This operation destroys the process

public interface MyProcessMBean {

   public String getProcessName();
   public String getProcessMask();
   public boolean isProcessRunning();
   public String getProcessHost();
   public void setProcessPort(int port);
   public int getProcessPort();

   public void startProcess();
   public void stopProcess();
   public void haltProcess(Integer halt);       
}

Now, that you've got your MBean, it's time to test it!

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