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opEvents can process information from a variety of sources, some of which can be extended to suit non-standard deployments. This document briefly documents how to configure opEvents' input sources.

Input Configuration

The inputs opEvents is supposed to handle are specified in the opevents section of conf/opCommon.nmis, primarily in subsection opevents_logs. opEvents primarily handles event information sourced by consuming and collating log files from sources like NMIS, Tivoli or general syslogs.

Here is an example configuration fragment:

 'opevents_logs' => {
  # parsertype => list of logfiles (or dirs for nmis_json_dir)
  # natively supported: tivoli_log, cisco_syslog, nmis_traplog, 
  # nmis_eventlog, nmis_slavelog and nmis_json_dir
  'cisco_syslog' => [ '<nmis_logs>/cisco.log', "/some/other/log.file" ],
  'tivoli_log' => [ '<nmis_logs>/tivoli.log' ],
  'nmis_traplog' => [ '<nmis_logs>/trap.log' ],
  'nmis_slavelog' => [ '<nmis_logs>/slave_event.log' ],
  'nmis_eventlog' => [ '<nmis_logs>/event.log' ],
  # attention: json logs in this directory are REMOVED after consumption
  # 'nmis_json_dir' => [ '<nmis_logs>/json' ],

The natively understood formats are:

Format Name
(Parser Type)
nmis_eventlogAn event log file created by NMIS
nmis_slavelogAn NMIS poller event log file
nmis_traplogAn NMIS trap log file
nmis_json_dirA directory of NMIS event logs in JSON format
cisco_syslogA Syslog log file containing logs created by Cisco devices

A Tivoli log file

To enable a particular log file or format, you need to add an entry for the  log file in question to the list of files for the appropriate log format; check the  cisco_syslog entry in the example above for the syntax. The tokens <nmis_something> in the example work like centrally-defined shortcuts or macros; they are replaced by the actual locations given in the directories section at the beginning of conf/opCommon.nmis.

opEvents handles non-existent log files gracefully, but the log formats need to match the actual content. All log files are reopened on demand (e.g. when log rotation renames a file), and checked at least once every opeventsd_update_rate seconds. The order of log file specifications is not relevant.

Please note that the selection of the built-in parsers is tied to the value of the format name; all custom parsers that you might define must have their own, unique format names which must not clash with any of the built-in parser types.

Black and Whitelisting

opEvents ships with ready-made black and whitelist rules to reduce voluminous inputs down to the relevant details, but these can be adjusted at need. These lists are active if the settings  black_list_enabled or white_list_enabled are set to "true", respectively.

The black list contains a set of filtering rules which remove matching log entries from opEvents' input stream. The white list rules can be used to ensure that matching input entries are processed; if the white list is enabled, then only events matching the white list will be processed (but raw logging is still performed for forensics purposes). Enabling both black and white list options simultaneously is not useful.

Both black and white lists are configured in conf/EventListRules.nmis, in sections like this example:

'blackList' => { 
 '10' => 'NTP Core \(INFO\)',
 '20' => 'OLD-CISCO-TS-MIB::tslineSesType\.6\.1=tcp',
 '30' => 'CISCO-SYSLOG-MIB::clogMessageGenerated',
'whiteList' => {
 '1' => 'TIVOLI\|\w+\|ams',
 '10' => 'SYS-[0123]-\w+',
 '20' => 'LINEPROTO',
 '30' => 'OSPF-\d-ADJCHG',

The format is straight-forward: the numeric key controls order of rule application, and the right side is a regular expression that the log entries are matched against.

Normalisation and Enrichment

For the natively-supported log formats (except nmis_json_dir) only the actual parsing is hard-coded; the act of subsequent further extraction and collection of relevant details is configurable - but of course opEvents ships with a substantial set of default normalisation rules. Event normalisation consists of associating a log entry with a node, extracting details, determining whether the event is stateful or stateless, followed by optional additional enrichment from external sources.

Normalisation is controlled by the configuration files conf/EventSyslogRules.nmis, EventNmisRules.nmisEventTivoliRules.nmis and EventTrapRules.nmis, all of which have a similar format. Here is an example config fragment from the syslog rules:

'rules' => {
 '1' => {
	 event => 'Interface Down',
	 regex => qr/LINEPROTO-5-UPDOWN:.+down/,
	 stateful => 'Interface',
	 priority => 1,
 '10' => {
 	 regex => qr/Interface (\w+[\d\/\.]+)/,
 	 name => 'element',

The key component is the rules section, which controls what details are extracted from a log entry and how they are saved a sevent properties. There are a few ways of augmenting the event with information:

  • if both regex and name directives are present and if the regex matches and captures something from the log entry, then a named property (with name from the name directive) will be created, with the value being the captured content.
  • The regex matching is performed on most of log input, but different across the various parsers:
    For parser types other than nmis_eventlog and nmis_slavelog the regex is applied to the event details property, which at this point holds most of the input log entry (usually everything except node and timestamp)
    For the event log parsers, the match is applied to:
    1. only to the event property named by the directive variable if that directive is present (e.g. 'variable' => 'node'),
    2. or to the whole, unsplit input log entry.
  • Parser types except nmis_eventlog and nmis_slavelog: if a rule block contains a regex directive which matches, then any key-value entries for event, prioritystate or stateful in that rule block will be copied to the event as static properties.

(You might also encounter the deprecated legacy format of using directives name and value to set just one property to a fixed value.)

In the example above, rule 1 will be active if a "line protocol down" log entry is detected, and in that case it'll add properties "priority", "event", and "stateful", all with static values. Rule 10 will be active if the log entry contains "Interface <something>", and it'll copy over the matched <something> as the value of the property named "event".

All normalisation rules are checked in sequence of their numeric key, and all the ones whose regex directive matches will contribute to the new event's properties. Normalisation and enrichment then continues using information from NMIS; events are associated with the relevant nodes, stateful deduplication is performed etc.

Further enrichment can be performed using policy actions (using the tag.tagname() action), enrichment statements in correlation rules or from external databases.

Please note that the log file format nmis_json_dir is not subject to normalisation; instead the contents of these are expected to be normalised already.

Command-line Event Creation

To provide a simple interface for external programs, opEvents also can create an event "on the fly" with event details from command-line arguments or a JSON file.

To create an event on the fly, you have to call with the argument act=create-event, which causes it to use all further key=value pairs in the arguments to construct an event, like this example: act=create-event event=testevent node="somenode" details="this is just a test event" action_required=1 action_checked=0 priority=4

Your event is expected to contain all required event properties and no further normalisation is performed.  The option action_required should be set to 1 so that opEvents will process the event with Action Policies, or 0 to have opEvents not process with action policies.

Alternatively you can save your desired event's properties in a file in JSON format, and use act=create-json to instruct opeventsd to create an event from it: act=create-json path=./myevent_in_format.json

Generic Extensible Parser

In situations where none of the built-in input mechanisms are suitable you can also define your own generic parser rules to integrate just about any text-based log information into opEvents.

The generic parser is activated by the configuration option opevents_parser_rules, in conf/opCommon.nmis, and the rules are defined in conf/EventParserRules.nmis. Hiere is an excerpt from the generic parser rules example that opEvents ships with:

'cisco_alternate' => {
 1 => {
 	"IF" => qr/%/, # no cisco log if no % present
 	"THEN" => {
 		  # match date/time, host and details
		  10 => {
			 IF => qr/^(\S+\s+\d+\s+[\d:]+)\s+(\S+)[^%]+%(.+)$/,
			 THEN => "capture(date,host,details)",
		  # some units have Local instead of hms
		 11 => {
			 IF => qr/^(\S+\s+\d+)\s+Local\s+(\S+)[^%]+%(.+)$/,
			 THEN => "capture(date,host,details)",
		 # match event name, could have done that in one of the regexp above
		 20 => {
			 IF => qr/%(\w+\-\d-\w+):/,
			 THEN => "capture(event) AND capture(syslog)", # save this in two places
 		 '23' => {
			 IF => qr/%BGP-5-ADJCHANGE: neighbor (\d+\.\d+\.\d+\.\d+) Down/,
			 THEN => 'capture(element) AND set.event(BGP Neighbor Down) AND set.state(down) AND set.priority(4) AND set.stateful(BGP Neighbor)',

The format is straight-forward: the top key allocates a new log format type (here cisco_alternate) which you would use in opevents_logs for your log files. This parser type or format name must be distinct and not clash with any built-in parsers (e.g. creating a parser type "nmis_eventlog" won't work).

Under that key there are any number of (nested) capture rules, which control what to match in an input, and how to copy material to the newly created event. These rules use a format very similar to the Event Actions and Escalation policies: IF defines a regular expression that the log entry has to match, THEN declares what to do in that case, and a successful rule with optional BREAK statement skips the rules on the same nesting level.

The THEN expression consists of a nested sub-policy or of an action statement.

Before opEvents 2.2 the action statement must be an single string containing an AND-separated list of directives; from opEvents 2.2 onwards it can also be an explicit list of directives (which is faster and more flexible; see the EventParserrules.nmis that ships with opEvents for a Best-current-practice example).

In both cases the action statement must contain one or more of the supported directives:

  • set.propertyname(value) sets the named property to the static value.
    No quoting of the value is required or supported.
    The character ")" cannot be part of the value before opEvents 2.2; In 2.2 and above it may only be present if you use the explicit list format for your action statement.
  • capture(propname1,propname2,...) saves the respective captures from the regex in the named properties. The captures are assigned in their order in the regular expression; if you want grouping but not capturing, use (?:....) in your regex. Note that you cannot use multiple capture statements in one THEN.
  • opEvents version 2.0  introduces the new action ignore. This aborts all parsing of this input line altogether and no event is created for it.
    Normally the generic parser is expected to extract suitable information for an event from every single input line, which might not work well if your log data is coming from multiple sources or can't be suitably prefiltered.
  • In opEvents version 2.2 we've added the directives  resolve.fwd(propname) and resolve.rev(propname).
    The resolve.fwd() directive expects the property to be a DNS name and queries the DNS for an IP address associated  with the name; the resolve.rev() directive interprets the property as an IP address and looks for a host name for it. If the resolution is successful, the property value is replaced by the DNS data; otherwise the property is left as-is.
    e.g. to resolve a BGP Peer address which is stored in the element name, add an entry to DNS or /etc/hosts and include resolve.rev(element) as a parser directive.
  • opEvents 2.2 also adds the new directive plugin(PluginName), which invokes an external parser plugin for further enrichment or modification of the event.
    This functionality is described in more detail in the next section.

Rules are applied in ascending order, defined by their numeric key, and nesting is fully supported.
Note that the numeric key may contain fractional numbers (e.g. "14.8"), which makes it very easy to insert new rules between existing ones.

opEvents 2.0.6 and newer ships with complete generic parser rules for parsing Cisco syslogs (log format type "cisco_alternate") and SNMP trap logs (log format type "nmis_traplog_alternate"), which you may want to use instead of the default built-in parsers if your log material requires custom processing.

Parser Plugins

For situations where external input must be incorporated into events at the time of parsing, opEvents 2.2 and newer support  user-defined parser plugins.
The directory install/parser_plugins contains an example plugin called and a README file with documentation.


All plugins must be valid Perl code. The files must be named and reside in the directory conf/parser-plugins. Each plugin must have a proper 'package Something;' namespace declaration that matches the file name, and this package namespace must not clash with any existing opEvents or NMIS components.

It's recommended that the plugin have a version declaration right after the package namespace declaration, e.g.. 'our $VERSION = "1.2.3";'
The '1;' line at the end of the file is required and must not be omitted.

The plugin may load extra Perl modules with 'use', but it must not use any package-level global variables. All its variables and any objects that it might create must have local scope. The plugin must not use Exporter to export anything from its namespace.

Plugin Interface

A plugin must offer a function called parse_enrich or it will be ignored by opEvents.

When triggered by a plugin(SomeName) parser directive, the parse_enrich function of that plugin will be called with two arguments, line and event (in that order).

  • Line is the complete log entry/line that is being processed and cannot be modified.
  • Event is a hash reference and contains the preliminary live data structure of the event as parsed so far.
    Event properties can be changed, added and deleted by the plugin function by modifying this live event hash.

The parse_enrich function must return one of the following:

  • 1: to indicate that it succeeded,
  • 0 or undef: to indicate that event parsing should be aborted for this line and no event should be created (like the parser directive ignore),
  • or any other string value as an error message (which will be logged).

Any changes made to the event properties are ignored unless the function completes successfully and returns 1. This also applies to a crashing parse_enrich function, or if is terminated because it ran over time.

Plugin Configuration

The configuration option opevents_plugin_max_runtime (default: 5 seconds) sets the maximum execution time for a single parse_enrich call. If a plugin's function runs longer than that it is terminated and an error message is logged; any changes that it may have made to the live event datastructure are ignored in this case.

Plugin Activation

A generic extensible parser rule can invoke one or more parser plugins using the action directive plugin(PluginName).

When such a plugin call directive is encountered for the first time, the opEvents daemon loads (and caches) all available plugins that meet the requirements. To reread modified plugins, opeventsd must be restarted.

If a plugin named 'PluginName' is available, its parse_enrich function is executed and if successful, the modifications made by the function replace the event properties. Parsing then continues normally.