alarm_handler (3erl)

The alarm handler process is a gen_event event manager process which 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 start-up, 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 of them in a list which can be passed to a user defined event handler, which may be installed at a later stage. The list can grow large if many alarms are generated. So it is a good reason to install a better user defined handler.

There are functions to set and clear alarms. The format of alarms are defined by the user. For example, an event handler for SNMP could be defined, together with an alarm 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 may 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. Refer to gen_event(3erl) for further details.

clear_alarm(AlarmId) -> void()

Types:

AlarmId = term()

Sends the clear_alarm event to all event handlers.

When receiving this event, the default simple handler clears the latest received alarm with id AlarmId.

get_alarms() -> [alarm()]

Returns a list of all active alarms. This function can only be used when the simple handler is installed.

set_alarm(alarm())

Types:

alarm() = {AlarmId, AlarmDescription}

AlarmId = term()

AlarmDescription = term()

Sends the set_alarm event to all event handlers.

When receiving this event, the default simple handler stores the alarm. The AlarmId identifies the alarm and is used when the alarm is cleared.

error_logger(3erl), gen_event(3erl)