Writing Monitors for the Event Monitoring Service (December 1999)

Chapter 3 107

Creating a Resource Monitor

Processing a Resource Update Event

The Resource Update Event occurs when the EMS API needs an update

on the value of a resource. The resource monitor should be developed to

respond to this event by obtaining the current value of the resource. The

polling interval between Resource Update Events is set by the client

application in the monitor request. The EMS API will send Resource

Update Events to the resource monitor at every polling interval, and the

resource monitor will respond by returning the current value of the

resource.

After obtaining the current resource value, the resource monitor will call

rm_notify(), which sends the current resource value to the EMS API. If

the resource value meets the notiﬁcation criteria, rm_notify() will send

a Notiﬁcation Message to the target application.

The Resource Update Event is speciﬁed by a return_type of

RM_RESOURCE_UPDATE_EVENT from rm_get_next_event().

Replying to Resource Update Events

To respond to a resource update event for your resource monitor, include

the following information.

• Check that the resource requested is supported

• Get the current value for that resource. If the monitor has an error

trying to obtain the value:

Determine how the monitor proceeds when it receives an error while

trying to obtain the value. The choices are:

— set RmResourceType = RM_ERROR_TYPE

— or set the RmResourceValue to some deﬁned error state or value

• Set RmMonitorReturnData.

This applies if the monitor has any speciﬁc details of information

about the resource or current value.

If using character/ascii data in MonitorReturnData ﬁeld, append null

terminator (\o) and include null terminator (strlen+1) in the

RmMonitorReturnDataLen.