Availability Guide for Application Design

Instrumenting an Application for Availability
Availability Guide for Application Design—525637-004
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DSM Management Services
Event Message Collectors
EMS supports two types of event message collector processes:
•
A primary collector
•
Alternate collectors
Each system (or node) has only one primary event message collector, named $0. It is
configured during system generation and always runs as a process pair. $0 is the
primary collection point for all event messages generated by all reporting subsystems
in a system.
Alternate collectors offer an alternative to the central collection point provided by the
primary collector $0. Alternate collectors provide functions similar to those supplied by
$0, but each alternate collector maintains its own log files. The separation of events
into several log files speeds up event processing, because a network management
application program does not have to read a single large file containing many events
unrelated to that management application.
The collectors write messages to event log files or alternate log files. You can use
alternate log files, for example, to separate your system and application environments.
The primary event log is maintained by the primary collector ($0). Alternate collectors
write messages to their own logs. To use an alternate collector, your application must
explicitly send its events to specific alternate collectors.
Event Message Distributors
EMS provides four distributor processes that collect event messages from the event
log file (or alternate log files): a consumer distributor, a printing distributor, and a
forwarding distributor. These processes distribute these operator messages to various
destinations. The printing distributor formats the event messages. The forwarding and
consumer distributors deliver events in tokenized buffers.
The consumer distributor is used by both HP and user-written applications to read the
EMS event messages in the EMS log file (or alternate log files), depending on the filter
specifications loaded with the distributor. The consumer distributor reads all events and
applies the filters to decide which events should be distributed and which should be
suppressed. The application can take appropriate action, if necessary, in response to
an important event. NonStop NET/MASTER is an example of an operations console
application that uses the consumer distributor.
The printing distributor reads EMS event messages in the EMS log file (or alternate log
files) and formats the event messages into operator messages for logging to disk files,
terminals, or printers.
The forwarding distributor filters specific events and sends them to an EMS collector
process on another system in the network. The EMS collector process on the
destination system saves forwarded event messages in its EMS event log file.