HP-UX Event ManagerProgrammer's Guide

1 Introduction
The Event Manager is a comprehensive event management system. It includes a full set of
command-line utilities that enable you to filter, sort, and format events. An event is an indication
that some changes have happened in the system that may be of interest to a class of users or
different entities within a system. Following are the interested groups and entities:
• A system administrator, application manager, or some other class of users
• System monitoring software
• The operating system
• An application program
This chapter addresses only user-level event handling. Events can be captured on a local system.
This chapter addresses the following topics:
• “Events and Event Management” (page 11)
• “How EVM Events are Handled” (page 12)
Events and Event Management
EVM provides a centralized means of posting, distributing, storing, and reviewing event
information. These features are supported regardless of the event channel used by individual
event posters, and without requiring the existing posters to change how they interact with their
current channels. EVM makes event information easily accessible to the system administrators.
It also provides a flexible infrastructure that can be used as an event distribution channel by the
following:
• Development groups
• Independent software vendors
• Customer-application developers
• Other event channels
The mechanism used to pass event information is called event notification, and the component
generating the event is known as the event poster. The EVM event-posting mechanism is a
one-way communication channel. It enables the poster to communicate information to any entity
that accesses it. The poster need not know which entities, if any, are interested in accessing an
event that is posted.
An entity that expresses an interest in receiving event information is called an event subscriber.
Depending on the type of event, subscribers can include system administrators, other software
components, or ordinary users. Some events are never be subscribed to.
Events can be posted and subscribed to by any process, and the same process can be both a poster
and a subscriber. However, in all cases, the ability to post and access specific events is governed
by security authorizations.
In the simplest case, an event channel is a static ASCII log file containing event information from
a single source, which a user can view by means of standard UNIX tools (for example, more).
EVM provides a single point of focus for multiple event channels by combining events from all
sources into a single event stream. Interested parties can either monitor the combined stream in
real time or view historical events retrieved from storage. The EVM viewing facilities include a
full set of command-line utilities, which enable the events to be filtered, sorted, and formatted
in a variety of ways. You can also configure EVM to perform automatic notification of selected
conditions.
Events and Event Management 11