Script for posting to Slack's incoming webhooks

post_to_slack.rb

require 'json'
require 'optparse'
require 'net/http'
require 'net/https'

def parse_options(argv)

  #######################################
  # Please change the following as needed
  #######################################

  slack_post_url        = 'https://hooks.slack.com/services/ImALongString'
  slack_user_name       = 'Monit'
  slack_user_emoji      = ':interrobang:'
  slack_channel_name    = '#badthingsarehappening' # remember to prepend a hashtag 
  app_name              = 'AwesomeApp'
  default_message_color = '#439FE0' # a nice neutral blue as default

  #######################################

  opts = {}
  opts[:slack_options] = {}
  opts[:slack_options][:attachments] = []

  attachment = {}
  attachment[:fields] = []

  # fields
  service = {}
  service[:title] = "Service"
  service[:short] = "true"
  message = {}
  message[:title] = "Message"
  server = {}
  server[:title] = "Server"
  server[:short] = "true"
  user = {}
  user[:title] = "User"
  user[:short] = "true"

  @parser = OptionParser.new do |o|

    ### Optional options means they don't have to be set as part of the shell command, because they have defaults specified in the file.

    o.on '--slack-url URL', 'Slack URL to post to. Optional: Yes Defaults: Set in script Accepts: String' do |arg|
      opts[:slack_url] = arg
    end

    # Main body

    o.on '--name NAME', 'User name of the bot. Optional: Yes Defaults: Set in script Accepts: #String' do |arg|
      opts[:slack_options][:username] = arg
    end

    o.on '--channel CHANNEL', 'Slack channel to post to. Optional: Yes Defaults: Set in script Accepts: String' do |arg|
      opts[:slack_options][:channel] = arg
    end

    o.on '--app APP', 'Name of the app. Optional: Yes Defaults: Set in script Accepts: String' do |arg|
      opts[:slack_options][:text] = "*#{arg}* has sent a message:"
    end    


    o.on '--emoji EMOJI', 'Optional: Yes Defaults: Set in script as :interrobang: Accepts: :String:' do |arg|
      opts[:slack_options][:icon_emoji] = arg.gsub
    end

    # Attachment Options

    o.on '--alert ALERT', 'Alert level. Optional: Yes Defaults: Set in script as "#439FE0" (a nice neutral blue) Accepts: "good", "warning", "danger", or a RGB hex value.' do |arg|
      attachment[:color] = arg
    end

    o.on '--service SERVICE', 'Service involved. Optional: No Defaults: None Accepts: String' do |arg|
      service[:value] = arg
    end

    o.on '--message MESSAGE', 'Message. Optional: No Defaults: None Accepts: String.' do |arg|
      message[:value] = arg
    end

    o.on '--host HOST', 'Originating host. Optional: Yes Defaults: Value of hostname command Accepts: String' do |arg|
      server[:value] = arg
    end    

    o.on '--user USER', 'Originating user. Optional: Yes Defaults: Value of whoami command Accepts: String' do |arg|
      user[:value] = arg
    end    

  end

  @parser.banner = "post_to_slack [options]"

  @parser.parse!(argv)

  # defaults
  
  opts[:slack_url]                      ||= slack_post_url
  opts[:slack_options][:channel]        ||= slack_channel_name 
  opts[:slack_options][:username]       ||= slack_user_name
  opts[:slack_options][:icon_emoji]     ||= slack_user_emoji
  opts[:slack_options][:text]           ||= "*#{app_name}* has sent a message:"

  attachment[:fallback]                 ||= "Please use a platform that can see formatted messages :P"
  attachment[:color]                    ||= default_message_color 

  server[:value]                        ||= `hostname`.strip
  user[:value]                          ||= `whoami`.strip

  # add fields to the attachment
  attachment[:fields] << server
  attachment[:fields] << user
  attachment[:fields] << service
  attachment[:fields] << message  

  # add attachment to the message
  opts[:slack_options][:attachments] << attachment

  opts
end

parsed_options = parse_options(ARGV)

uri           = URI.parse(parsed_options[:slack_url])
https         = Net::HTTP.new(uri.host,uri.port)
https.use_ssl = true

req           = Net::HTTP::Post.new(uri.path, initheader = {'Content-Type' =>'application/json'})
req.body      = parsed_options[:slack_options].to_json
puts req.body

res           = https.request(req)

Monit's native alerts has the virtue of only alerting once when defined tests have failed. However this slack messages sending is "stateless" and will be triggered every time when the test fails. Is there a good way to make it behaving similarly like native email alerts?