Module java.management
Package javax.management.monitor

Class CounterMonitor

java.lang.Object
javax.management.NotificationBroadcasterSupport
javax.management.monitor.Monitor
javax.management.monitor.CounterMonitor
All Implemented Interfaces:
MBeanRegistration, CounterMonitorMBean, MonitorMBean, NotificationBroadcaster, NotificationEmitter
public class CounterMonitor
extends Monitor
implements CounterMonitorMBean
Defines a monitor MBean designed to observe the values of a counter attribute.

A counter monitor sends a threshold notification when the value of the counter reaches or exceeds a threshold known as the comparison level. The notify flag must be set to true.

In addition, an offset mechanism enables particular counting intervals to be detected. If the offset value is not zero, whenever the threshold is triggered by the counter value reaching a comparison level, that comparison level is incremented by the offset value. This is regarded as taking place instantaneously, that is, before the count is incremented. Thus, for each level, the threshold triggers an event notification every time the count increases by an interval equal to the offset value.

If the counter can wrap around its maximum value, the modulus needs to be specified. The modulus is the value at which the counter is reset to zero.

If the counter difference mode is used, the value of the derived gauge is calculated as the difference between the observed counter values for two successive observations. If this difference is negative, the value of the derived gauge is incremented by the value of the modulus. The derived gauge value (V[t]) is calculated using the following method:

  • if (counter[t] - counter[t-GP]) is positive then V[t] = counter[t] - counter[t-GP]
  • if (counter[t] - counter[t-GP]) is negative then V[t] = counter[t] - counter[t-GP] + MODULUS
This implementation of the counter monitor requires the observed attribute to be of the type integer (Byte, Integer, Short, Long).
Since:
1.5