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Prerequisites
NMIS version 8.3.18G or greater.
Basic Alerts
An alert is a custom event generated by testing the value of an OID or custom variable and producing a boolean result (true or false). If the test returns true, an event is raised and it will run through the escalation system, false will not raise an alert. Later on, when the test that was returning true once again returns false the event will be cleared.
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A quick note on stringwise and numerically. If $r is 0, $r == 0 is true, $r eq "0" is also true. If $r is 00, $r == 0 is true, $r eq "0" is false. That's the basic idea.
Where to add the Alert
The alert can be added to current variables being polled from the devices, or a new section can be added. For example a new section in Model->system->sys could be added which might look like this, the --snip-- indicates that extra model code has been removed, this is provided as an example of the context for where to add this to the models.
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Adding the alert also adds the information to the "Device Details" panel, so you get the last polled value displayed all the time.
Example
The following is an example of the layout of an alert (in this example serialNum is taken from Model-CiscoRouter.nmis) and uses a string based (stringwise) comparison:
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'cipSecGlobalActiveTunnels' => {
'oid' => 'cipSecGlobalActiveTunnels',
'title' => 'Global Active Tunnels',
'alert' => {
'test' => '$r == 0',
'event' => 'No tunnels present',
'level' => 'Critical'
}
} |
More Advanced Alerts
Alerts can also be created in the 'alerts' section of the model (if the model does not have that section it can be added at the lowest level of the model, e.g. along side '-common=' and 'system'. Alerts created in this section have the advantage of being able to use values from a whole section of data to determine if the alert should be triggered or not. A concrete example always makes things more clear.
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'services' => -- defines what section the values being used for the alert are taken from. In this case services cannot be found in the model because it is a special section just for servers. Normally you will not need to worry about special sections.
'HighProcessMemoryUsage' => { – this creates a label/id for the alert
'type' => 'test' – this means the alert will test a single condition. The options are ['test', 'threshold-rising', 'threshold-falling']
'test' => 'CVAR1=hrSWRunPerfMem;$CVAR1 > 300000', – defines a custom variable and then uses that variable to perform a boolean test. NOTE: in test mode only one custom variable can be used
'value' => 'CVAR1=hrSWRunPerfMem;$CVAR1 * 1', – the value triggered the alert and that will be displayed when the alert is shown in the GUI
'unit' => 'KBytes', – the unit that the above value will be displayed with
'element' => 'hrSWRunName', – which OID/value that has the problem, a descriptor or identifier. In this case it is showing the name of the process that has high memory usage.
'event' => 'High Process Memory Usage', – the name of the event
'level' => 'Warning' – the level the event will be triggered as. When using thresholding this is not used as the threshold defines the level
Thresholds
While boolean tests are nice it is often much more useful to specify levels of acceptance instead of just on or off, thresholds allow us to do this. Another example:
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