Writing Monitors for the Event Monitoring Service (December 1999)

Chapter 3 73
Creating a Resource Monitor
Defining the Resource Dictionary Hierarchy
• DESCRIPTION: text
Optional. The DESCRIPTION allows humans to understand what
information a particular resource class or instance provides. It
displays when a user selects “View Description” in MC/ServiceGuard,
MC/LockManager, or the SAM interface to EMS.
The description should be less than 80 characters, if possible, but it
can be up to 2047 characters. It cannot contain tabs or newline (\n)
characters. Because the text will stream without reasonable breaks it
is better to keep it to 80 characters or fewer to ensure legibility in the
SAM interface to EMS.
Make the description as descriptive as possible. Start the description
with a one-line title. Include the word “subclass” in the title, if the
resource is a subclass. If the resource is a resource instance, include
the resource name and any variables it requires. Make sure the
description explains what the resource is and, if appropriate, a list of
values it can have.
If the DESCRIPTION field is missing, the RmDescription field is set to
NULL for any resource monitor object that refers to this resource. The
RmDescription field is the location for lengthy descriptions. See the
section, “Subclass Objects” for information on using the
RmDescription field.
• MONITOR: monitor_name [ args ]
Optional. If the MONITOR keyword is missing, the resource is assumed
to be a resource class. In their subtree, resource classes must contain
at least one resource that is linked to a monitor. Resource classes that
do not are not visible to client applications.
If a monitor is written to return a list of resource instances in a
Subclass Reply and the subclass instances do not appear in the
resource dictionary, the MONITOR keyword appears in an entry for the
resource class.
monitor_name [ args ] is the invocation of the monitor, consisting of
the full path of the monitor executable plus any additional
command-line arguments. Shell expansion is not performed on the
arguments.
Note that two entries in the dictionary that specify the same MONITOR
command will result in only one copy of the monitor being started by
the Registrar.