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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>1996</year>
<year>2014</year>
<holder>Ericsson AB, All Rights Reserved</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
The Initial Developer of the Original Code is Ericsson AB.
</legalnotice>
<title>alarm_handler</title>
<prepared>Martin Björklund</prepared>
<responsible>Bjarne Dacker</responsible>
<docno></docno>
<approved>Bjarne Däcker</approved>
<checked>Martin Björklund</checked>
<date>1996-09-10</date>
<rev>A</rev>
<file>alarm_handler.sgml.t1</file>
</header>
<module>alarm_handler</module>
<modulesummary>An Alarm Handling Process</modulesummary>
<description>
<p>The alarm handler process is a <c>gen_event</c> 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.
</p>
<p>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.
</p>
<p>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.
</p>
<p>The alarm handler is part of the SASL application.
</p>
<p>When writing new event handlers for the alarm handler, the
following events must be handled:
</p>
<taglist>
<tag><c>{set_alarm, {AlarmId, AlarmDescr}}</c></tag>
<item>
<p>This event is generated by
<c>alarm_handler:set_alarm({AlarmId, AlarmDecsr})</c>.
</p>
</item>
<tag><c>{clear_alarm, AlarmId}</c></tag>
<item>
<p>This event is
generated by <c>alarm_handler:clear_alarm(AlarmId)</c>.
</p>
</item>
</taglist>
<p>The default simple handler is called <c>alarm_handler</c> and
it may be exchanged by calling <c>gen_event:swap_handler/3</c>
as <c>gen_event:swap_handler(alarm_handler, {alarm_handler, swap}, {NewHandler, Args})</c>. <c>NewHandler:init({Args, {alarm_handler, Alarms}})</c> is called. Refer to gen_event(3)
for further details.
</p>
</description>
<funcs>
<func>
<name>clear_alarm(AlarmId) -> void()</name>
<fsummary>Clear the specified alarms</fsummary>
<type>
<v>AlarmId = term()</v>
</type>
<desc>
<p>Sends the <c>clear_alarm</c> event to all event handlers.</p>
<p>When receiving this event, the default simple handler
clears the latest received alarm with id <c>AlarmId</c>.
</p>
</desc>
</func>
<func>
<name>get_alarms() -> [alarm()]</name>
<fsummary>Get all active alarms</fsummary>
<desc>
<p>Returns a list of all active alarms. This function can only
be used when the simple handler is installed.
</p>
</desc>
</func>
<func>
<name>set_alarm(alarm())</name>
<fsummary>Set an alarm with an id</fsummary>
<type>
<v>alarm() = {AlarmId, AlarmDescription}</v>
<v>AlarmId = term()</v>
<v>AlarmDescription = term()</v>
</type>
<desc>
<p>Sends the <c>set_alarm</c> event to all event handlers.</p>
<p>When receiving this event, the default simple handler
stores the alarm. The <c>AlarmId</c> identifies the alarm
and is used when the alarm is cleared.
</p>
</desc>
</func>
</funcs>
<section>
<title>See Also</title>
<p>error_logger(3), gen_event(3)
</p>
</section>
</erlref>
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