Designing and Managing Behavior Models - Alarm Actions - Fire Trigger -
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Fire Trigger

In NerveCenter, you have several ways of generating a trigger. For instance, you can use a poll, a mask, or the FireTrigger() function to fire the trigger. You can also use the Fire Trigger alarm action to produce a trigger. This action is useful when you need one alarm to send a trigger to itself or to another alarm.

Here are some examples of when you might need to use the Fire Trigger alarm action:

• You want an alarm transition to fire a trigger on a delayed basis so that your alarm will know when a certain amount of time has passed.

  This strategy is used in the predefined alarm IfLinkUpDown, shown in IfLinkUpDown Alarm.

  IfLinkUpDown Alarm

  

  On the linkDown transition, this alarm fires the linkTimer trigger on a three-minute delay. If a linkUp trigger does not cause a transition to Ground within three minutes, the linkTimer trigger is fired, and the alarm transitions to the LinkDown state.

  Using the action for its timing capabilities is the most common use of the Fire Trigger action.

• You want to send information to an alarm instance about an event that is outside its scope.

  As an example, let's look at the predefined alarm BetterNode, which tracks the status of a node on a different subnet from the NerveCenter server.

  BetterNode Alarm

  

  If NerveCenter is unable to ping a node, the node's alarm instance transitions to the IcmpFail state. What happens next, however, depends on a trigger fired by an alarm instance monitoring the router that sits between the NerveCenter server and the node being monitored with BetterNode. If the alarm instance monitoring the router generates the routerUp trigger, the BetterNode alarm transitions to the critical NoResponse state, but if the router's alarm generates the routerDown trigger, the BetterNode alarm transitions to the normal RouterDown state.

• A behavior model requires alarms of different scopes to detect a condition.

  For example, suppose you want to create a behavior model that detects high interface traffic at the node level. You'll need to create a subobject scope alarm that detects high traffic on a single interface and fires a trigger that notifies a node scope alarm that the interface is busy. You'll also need a node scope alarm that tracks the triggers being fired by the subobject scope alarms. Behavior models of this type are called multi-alarm behavior models.

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     If you later turn an alarm off or reset the alarm to ground, any pending triggers fired by that alarm are cleared if the Clear Triggers for Reset To Ground or Off checkbox is checked in the alarm's definition window.

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  To add a Fire Trigger action to an alarm transition:

1. From the Transition Definition window, select the New Action button.

   A pop-up menu listing all alarm actions is displayed.

2. Select Fire Trigger from the pop-up menu.

   The Fire Trigger Action dialog is displayed.

   

3. In the Trigger Name field, specify the name of the trigger to be fired when the transition occurs.

   You can either type in the name of a new or existing trigger or select the name of an existing trigger from the Trigger Name drop-down list.

4. Either leave the default values in the SubObject, Node, and Property fields, or enter new values using the keyboard or the associated drop-down lists.

   If you want your Fire Trigger action to simply provide a timer for its own alarm instance, the default values are fine. The defaults ensure that the resulting trigger affects only alarm instances concerning the same node and subobject as the current alarm instance.

   If the trigger being fired will affect instances of a different alarm, you may need to change the default values. The steps below explain the values you can provide for these attributes.

   1. To change the value in the SubObject field, either type in a new value or select a value from the SubObject drop-down list.

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         When choosing a SubObject value, keep in mind that alarm instances with subobject scope must reference the same subobject in order to be transitioned by this trigger. For transitions with instance scope, only the instances must match; the base objects can be different. Any alarm instances with a node or enterprise scope will ignore the value in the SubObject field.

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      Values for the SubObject Field lists the acceptable values for the SubObject field.

      Values for the SubObject Field

      Value	Explanation
      $SO	The trigger inherits the originating alarm's subobject. This is the default.
      $ANY	The trigger is assigned a subobject that matches any destination alarm subobject. Think of this as a subobject wildcard.
      $ON.$OI	If the originating alarm has a subobject that consists of a base object plus an instance joined by a period, the trigger inherits the originating alarm's subobject (same as $SO). However, if the originating alarm does not have this type of subobject, the trigger's subobject is null (see $NULL below).
      $ON	If the originating alarm has a subobject that consists of a base object plus an instance joined by a period, the trigger inherits the base object portion of the alarm's subobject and appends to this base object a period and a wildcard for the instance. The resulting trigger can drive alarm instances with a subobject containing a matching base object and any instance. For example, let's say that an alarm instance with the subobject ifEntry.3 fires a trigger using $ON. The trigger's subobject will be ifEntry.*, and the trigger will affect alarm instances with subobjects such as ifEntry.1, ifEntry.2, and so on. If the originating alarm instance does not have a subobject that consists of a base object plus an instance, $ON is equivalent to $NULL.
      $NULL	The trigger is assigned a null subobject. The only subobject scope alarm that can be affected by such a trigger is one that has a null subobject itself.
      baseObject.instance	You can type the subobject. The trigger's subobject is set to the subobject you specify, for example, ifEntry.3 or system.0.
      anyString	This feature enables you to take advantage of the matching rules for triggers and alarm transitions by making creative use of the subobject attributes of these objects. For example, you could use the name of an application as the subobject in order to correlate all events relating to that application.

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   2. To change the value of the Node field, either type in a new value or select a value from the Node drop-down list.

      Values for the Node Field lists the acceptable values for the Node field.

      Values for the Node Field

      Value	Explanation
      $NODE	The trigger inherits the originating alarm instance's node. This is the default.
      $ANY	The trigger is assigned a node that matches any destination alarm instance node. Think of this as a node wildcard.
      nodeName	You assign the name of any managed node to this attribute. Use the Node drop-down list to prevent spelling errors.

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   3. To change the value of the Property field, either type in a new value or select a value from the Property drop-down list.

      Values for the Property Field lists the acceptable values for the Property field.

      Values for the Property Field

      Value	Explanation
      $PROPERTY	The trigger inherits the originating alarm instance's property. This is the default.
      $NO_PROP	The trigger is assigned no property. In this case, NerveCenter ignores the trigger's property attribute when determining which alarm transitons the trigger can affect.
      property	The trigger is assigned the property you type in or select from the Property drop-down list.

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      When a trigger contains a property, the property group of the node found in a destination alarm instance's node data member must contain the trigger's property. Otherwise, no alarm transition will occur.

5. Select a delay for the trigger by entering a positive integer in the Delay text field and selecting the appropriate radio button: Days, Hours, Minutes, or Seconds.
6. Select the OK button in the Fire Trigger Action dialog.
7. Select the OK button in the Transition Definition window.
8. Select the Save button in the Alarm Definition window.