Overview

opEvents provides the ability for the adminstrator to customise an event's properties from a variety of inputs. For example, if a user wanted to set a specific priority for an event it can be done during the input parsing stages.  This article will provide a methodology for creating events from SNMP traps, via a generic extensible parser with EventParserRules.

The generic parser rules are defined in EventParserRules.nmis which  is found in the configuration directory /usr/local/omk/conf.  Please read the notes at the top of this file first as they are very informative as to what is possible in regard to the parser rules.

Evaluate The Traps To Be Processed

Create a list of SNMP traps that are required be processed by opEvents. 

Correlate Events Into Stateful Pairs

For this discussion we will assume that the concept of 'state' is desirable.  i.e. If there is a "down" event, there should be a corresponding "up" event, and opEvents should keep track of the state and ignore duplicate inputs. (It is possible that several "down" events could share a single "up" or clearing event.)

State

opEvents tracks state based on a tuple of three event properties.

...

                                51 => {
                                        IF => qr/IF-MIB::linkDown/,
                                        THEN => ["set.event(Interface Down)", "set.stateful(Interface)",
                                                                         "set.state(down)", "set.priority(3)" ],
                                },

Create Parser Rules

opEvents will process the trap log file as specified on opCommon.nmis.  When parsing the traps, at least the following properties should be extracted:

...

This article focuses on situations where customers want customization for the remaining fields.

Set the Element

Review all the SNMP traps to determine which OID best describes what will become the element property.  Write a regular expression that matches this.

...

Notice the regular expression will catch an number of digits following the '=' character.  This rule 'captures' the element.  In this way we can dynamically assign event properties based on a regular expression.

Set Other Properties

Generally the other properties that we wish to set can be done with one rule. Consider the following trap received by opEvents.

...