Humanized mutator output for not-so-boring sensu-core alerts

glyphify.json

{
  "mutators": {
    "glyphify": {
      "command": "/etc/sensu/mutators/glyphify.rb"
    }
  }
}

glyphify.rb

#! /usr/bin/env ruby
# frozen_string_literal: true
#
# Custom 'Humanized' Sensu Mutator for Slack based alerts
#
# USAGE:
#
#  
# NOTES:
#   Compatible with sensu-core (Ruby) https://docs.sensu.io/sensu-core/latest/  
#
# LICENSE:
#   Copyright (c) 2015-2020 Airbrake Technologies, Inc <support@airbrake.io>
#   Author Patrick Humpal <patrick@netvilla.net>
#   Released under the same terms as Sensu (the MIT license); see LICENSE
#   for details.

require 'sensu-mutator'

class Glyphify < Sensu::Mutator

  def human_check_status
    case @event['check']['status']
    when 0
      'OK'
    when 1
      'WARNING'
    when 2
      'CRITICAL'
    else
      'UNKNOWN'
    end
  end

  def mutate
    dashboard_url = "https://IP-ADDRESS-OF-YOUR-SENSU-DASH"
    dashboard_link = "#{dashboard_url}/#/client/sensu/#{@event['client']['name']}?check=#{@event['check']['name']}"

    case @event['check']['status']
    when 0
      output = <<-BODY
Check Name: #{@event['check']['name']}
Status: #{human_check_status()} (#{@event['check']['status']})

BODY
    when 2
      output = <<-BODY
Check Name: #{@event['check']['name']}

Status: #{human_check_status()} (#{@event['check']['status']})

Address: `#{@event['client']['address']}`

Dashboard Link: <#{dashboard_link}|Click here> for sensu dashboard
BODY
    end

    @event['check']['output'] = output
    @event.merge!(:mutated => true)
  end
end

slack-payload.eruby

{
  "icon_emoji": ":bell:",
  "attachments": [
    {
      "fallback": "<%= @event["check"]["output"] %>",
      "color": "<%= color %>",
      "title": "<%= @event["client"]["name"] %>",
      "text": "<%= @event["check"]["output"].gsub('"', '\\"') %>"
    }
  ]
}

slack-template.eruby

<%=
@event["check"]["output"]
%>

slack.json

{
  "handlers": {
    "slack": {
      "type": "pipe",
      "mutator": "glyphify",
      "command": "/etc/sensu/handlers/slack.rb"
    }
  },
  "slack": {
    "webhook_url": "{{ sensu_slack_webhook }}",
    "token": "{{ sensu_slack_token }}",
    "channel": "#{{ sensu_slack_channel }}",
    "message_template": "/etc/sensu/slack-template.eruby",
    "payload_template": "/etc/sensu/slack-payload.eruby",
    "bot_name": "sensu"
  }
}