Trigger

The event-trigger processor, triggers an action if the configured condition evaluates to true.

The condition is evaluated using the the Golang implementation of jq with the event message as a json input.

jq tutorial

jq manual

jq playground

Examples of conditions:

The below expression checks if the value named counter1 has a value higher than 90
```
.values["counter1"] > 90
```
This expression checks if the event name is sub1, that the tag source is equal to r1:57400
```
.name == "sub1" and .tags["source"] == "r1:57400" 
```

The trigger can be monitored over a configurable window of time (default 1 minute), during which only a certain number of occurrences (default 1) trigger the action.

Actions can be of two types:

HTTP action: trigger an HTTP request
gNMI action: trigger a Get or Set gnmi RPC

HTTP Action#

Using the HTTP action you can send an HTTP request to a remote server, by default the whole event message is added to request body as a json payload.

The request body can be customized using Go Templates that take the event message as input.

The HTTP action templates come with some handy functions like:

withTags: keep only certain tags in the event message.
for e.g: {{ withTags . "tag1" "tag2" }}
withoutTags: remove certain tags from the event message.
for e.g: {{ withoutTags . "tag1" "tag2" }}
withValues: keep only certain values in the event message.
for e.g: {{ withValues . "counter1" "counter2" }}
withoutTags: remove certain values from the event message.
for e.g: {{ withoutTags . "counter1" "counter2" }}

processors:
  # processor name
  my_trigger_proc: # 
    # processor type
    event-trigger:
      # trigger condition
      condition: '.values["counter1"] > 90'
      # minimum number of condition occurrences within the configured window 
      # required to trigger the action
      min-occurrences: 1
      # max number of times the action is triggered within the configured window
      max-occurrences: 1
      # window of time during which max-occurrences need to 
      # be reached in order to trigger the action
      window: 60s
      # the action to trigger
      action:
        # action type
        type: http
        # HTTP method
        method: POST
        # target url, can be a go template
        url: http://remote-server:8080/
        # http headers to add to the request, this is a dictionary
        headers: 
          content-type: application/text
          # other-header: value
        # http request timeout
        timeout: 5s
        # go template used to build the request body.
        # if left empty the whole event message is added as a json object to the request's body
        body: '"counter1" crossed threshold, value={{ index .Values "counter1" }}'
        # enable extra logging
        debug: false

The below example triggers an HTTP GET to http://remote-server:p8080/${router_name} if the value of counter "counter1" crosses 90 twice within 2 minutes.

processors:
  my_trigger_proc:
    event-trigger:
      condition: '.values["counter1"] > 90'
      min-occurrences: 1
      max-occurrences: 2
      window: 120s
      action:
        type: http
        method: POST
        url: http://remote-server:8080/{{ index .Tags "source" }}
        headers: 
          content-type: application/text
        timeout: 5s
        body: '"counter1" crossed threshold, value={{ index .Values "counter1" }}'

gNMI Action#

Using the gNMI action you can trigger a gNMI Get or Set RPC when the trigger condition is met.

Just like the HTTP action the RPC fields can be customized using Go Templates

processors:
  # processor name
  my_trigger_proc: # 
    # processor type
    event-trigger:
      # trigger condition
      condition: '(.tags.interface_name == "ethernet-1/1" or .tags.interface_name == "ethernet-1/2") and .values["/srl_nokia-interfaces:interface/oper-state"] == "down"'
      # minimum number of condition occurrences within the configured window 
      # required to trigger the action
      min-occurrences: 1
      # max number of times the action is triggered within the configured window
      max-occurrences: 1
      # window of time during which max-occurrences need to 
      # be reached in order to trigger the action
      window: 60s
      # the action to trigger
      action:
        # action type
        type: gnmi
        # gNMI rpc, defaults to `get`, if `set` is used it will default to a set update.
        # to trigger a set replace, use `set-replace`
        rpc: set
        # the target router, it defaults to the value in tag "source"
        target: '{{ index .Tags "source" }}'
        # paths templates to build xpaths
        paths:
          - | 
            {{ if eq ( index .Tags "interface_name" ) "ethernet-1/1"}}
              {{$interfaceName := "ethernet-1/2"}}
            {{else}}
              {{$interfaceName := "ethernet-1/1"}}
            {{end}}
            /interfaces/interface[name={{$interfaceName}}]/admin-state
        # values templates to build the values in case of set-update or set-replace
        values:
          - "enable"
        # data-type in case of get RPC, one of: ALL, CONFIG, STATE, OPERATIONAL
        data-type: ALL
        # gNMI encoding, defaults to json
        encoding: json
        # debug, enable extra logging
        debug: false

The below example shows a trigger that enables a router interface if another interface's operational status changes to "down".

processors:
  interface_watch: # 
    event-trigger:
      debug: true
      condition: '(.tags.interface_name == "ethernet-1/1" or .tags.interface_name == "ethernet-1/2") and .values["/srl_nokia-interfaces:interface/oper-state"] == "down"'
      action:
        type: gnmi
        rpc: set
        target: '{{ index .Tags "source" }}'
        paths:
          - |
            {{ $interfaceName := "" }}
            {{ if eq ( index .Tags "interface_name" ) "ethernet-1/1"}}
              {{$interfaceName = "ethernet-1/2"}}
            {{ else if eq ( index .Tags "interface_name" ) "ethernet-1/2"}}
              {{$interfaceName = "ethernet-1/1"}}
            {{end}}
            /interface[name={{$interfaceName}}]/admin-state
        values:
          - "enable"
        encoding: json_ietf
        debug: true