Monitoring

The Monitoring service complies with the Java Management extensions specification and introduces a particular family of MBeans, the monitor MBeans, which enable you to observe the variation over time of attribute values of other MBeans. It does this by observing numerical values and strings. These monitor MBeans observe the attributes of another MBean, referred to as the observed MBean. The observed MBean is monitored at intervals specified by the granularity period. The type of the observed attribute is one of the types supported by the specific monitor sub-class which is used. The monitor derives a value from this observation, called the derived gauge. This derived gauge is either the exact value of the observed attribute, or the difference between two consecutive observed values of this attribute.

A notification is sent by the monitor MBeans when the value of the derived gauge satisfies one of a set of conditions. Thus monitor MBeans can notify other objects of several types of changes in the target. The conditions are specified when the monitor is initialized. Monitor MBeans may also send notifications when certain error cases are encountered during the observation.

Information on the value of an attribute within an MBean may be provided by three different monitors:

• Counter monitor -- observes attributes with integer types.

• Gauge monitor -- observes attributes with integer or floating point types.

• String monitor -- observes attributes with string types.

All three types of monitor MBeans extend the abstract Monitor class, which defines common attributes and operations.

For more information regarding the Monitoring service, refer to the Java Management Extensions Instrumentation and Agent Specification, v1.0 document.