Simplest HTTP+JSON sensu plugin

check-http-json.rb

#! /usr/bin/env ruby
# check-simple-http-json - show how to check a url, grab its json, and 

require 'sensu-plugin/check/cli'
require 'json'
require 'net/http'
require 'uri'

class CheckSimpleHttpJson < Sensu::Plugin::Check::CLI
    option :url,
        description: 'URL',
        short: '-u URL',
        long: '--url URL',
        default: 'http://localhost/'

    option :key,
        description: 'JSON Key',
        short: '-k KEY',
        long: '--key KEY',
        default: 'foo'

  option :warn,
         short: '-w N',
         long: '--warn N',
         description: 'WARNING threshold',
         proc: proc(&:to_i),
         default: 9000

  option :crit,
         short: '-c N',
         long: '--crit N',
         description: 'CRITICAL threshold',
         proc: proc(&:to_i),
         default: 4500

    def get(url)
        url = URI.parse(url)
        response = Net::HTTP.get_response(uri)
        JSON.parse(response.body)
    rescue Errno::ECONNREFUSED
        warning 'Connection refused'
    rescue JSON::ParserError
        warning 'Invalid JSON'
    end

    def run
        resource = get(config[:url])
        value = resource[config[:key]]
        message "#{config[:url]}##{config[:key]} #{value}"
        if value >= config[:crit]
            critical
        elsif value >= config[:warn]
            warning
        else
            ok
        end
    end
end