An Alarm Handling Process
The alarm handler process is a
gen_event
event manager process that receives alarms in the system.
This process is not intended to be a complete alarm handler.
It defines a place to which alarms can be sent. One simple event
handler is installed in the alarm handler at startup, but users
are encouraged to write and install their own handlers.
The simple event handler sends all alarms as info reports to the error logger, and saves all in a list. This list can be passed to a user-defined event handler, which can be installed later. The list can grow large if many alarms are generated. This is a good reason to install a better user-defined handler.
Functions are provided to set and clear alarms. The alarm format is defined by the user. For example, an event handler for SNMP can be defined, together with an alarm Management Information Base (MIB).
The alarm handler is part of the SASL application.
When writing new event handlers for the alarm handler, the following events must be handled:
{set_alarm, {AlarmId, AlarmDescr}}
This event is generated by
alarm_handler:set_alarm({AlarmId, AlarmDecsr})
.
{clear_alarm, AlarmId}
This event is
generated by alarm_handler:clear_alarm(AlarmId)
.
The default simple handler is called alarm_handler
and
it can be exchanged by calling
gen_event:swap_handler/3
as gen_event:swap_handler(alarm_handler, {alarm_handler, swap},
{NewHandler, Args})
. NewHandler:init({Args, {alarm_handler,
Alarms}})
is called. For more details, see
gen_event(3)
in STDLIB.
Functions
AlarmId = term()
Sends event clear_alarm
to all event handlers.
When receiving this event, the default simple handler
clears the latest received alarm with id AlarmId
.
Returns a list of all active alarms. This function can only be used when the simple handler is installed.
alarm() = {AlarmId, AlarmDescription}
AlarmId = term()
AlarmDescription = term()
Sends event set_alarm
to all event handlers.
When receiving this event, the default simple handler
stores the alarm. AlarmId
identifies the alarm
and is used when the alarm is cleared.