Package: javax.management.monitor

Overview

Provides the definition of the monitor classes. A Monitor is an MBean that periodically observes the value of an attribute in one or more other MBeans. If the attribute meets a certain condition, the Monitor emits a MonitorNotification.

The exact behavior of monitors is detailed in the JMX Specification. What follows is a summary.

There are three kinds of Monitors:

  • A CounterMonitor observes attributes of integer type. The attributes are assumed to be non-negative, and monotonically increasing except for a possible roll-over at a specified modulus. Each observed attribute has an associated threshold value. A notification is sent when the attribute exceeds its threshold.

    An offset value can be specified. When an observed value exceeds its threshold, the threshold is incremented by the offset, or by a multiple of the offset sufficient to make the threshold greater than the new observed value.

    A CounterMonitor can operate in difference mode. In this mode, the value compared against the threshold is the difference between two successive observations of an attribute.

  • A GaugeMonitor observes attributes of numerical type. Each observed attribute has an associated high threshold and low threshold.

    When an observed attribute crosses the high threshold, if the notify high flag is true, then a notification is sent. Subsequent crossings of the high threshold value will not trigger further notifications until the gauge value becomes less than or equal to the low threshold.

    When an observed attribute crosses the low threshold, if the notify low flag is true, then a notification is sent. Subsequent crossings of the low threshold value will not trigger further notifications until the gauge value becomes greater than or equal to the high threshold.

    Typically, only one of the notify high and notify low flags is set. The other threshold is used to provide a hysteresis mechanism to avoid the repeated triggering of notifications when an attribute makes small oscillations around the threshold value.

    A GaugeMonitor can operate in difference mode. In this mode, the value compared against the high and low thresholds is the difference between two successive observations of an attribute.

  • A StringMonitor observes attributes of type String. A notification is sent when an observed attribute becomes equal and/or not equal to a given string.

Package Specification

Interfaces

Classes