Foreign code, refactored

foo.rb

#!/usr/bin/env ruby

require "json"
require "net/http"
require 'trollop'
require 'statsd'

Statsd.host = 'localhost'
Statsd.port = 8125

opts = Trollop.options do
  opt :warn, "Warning threshold",  type: Integer, default: 1000
  opt :crit, "Critical threshold", type: Integer, default: 10000
end

begin
  uri      = URI.parse("http://localhost:8080/metrics")
  http     = Net::HTTP.new(uri.host, uri.port)
  request  = Net::HTTP::Get.new(uri.request_uri)
  response = http.request(request)

rescue Errno::ECONNREFUSED
  puts "CRITICAL - Connection Refused"
  exit 2
end

unless response.code == "200"
  puts "CRITICAL - Not 200 OK"
  exit 2
end

Channel             = Struct.new(:name, :size) do
  def to_s
    "#{name}: #{size}"
  end
end

json                = JSON.parse(response.body)
channels            = json.select { |_k,v| v["Type"] == "CHANNEL" }.map { |name, data|
  Channel.new(name.sub(/\ACHANNEL\./, ""), data["ChannelSize"].to_i)
}
max_size            = channels.map(&:size).max

if max_size >= opts[:crit]
  status = :critical
elsif max_size >= opts[:warn]
  status = :warning
else
  status = :ok
end

size_limit          = {ok: 0, warn: opts[:warn], critical: opts[:crit]}[status]
exit_code           = {ok: 0, warn: 1, critical: 2}[status]
relevant_channels   = channels.select { |channel| channel.size >= size_limit }

channels.each do |channel|
  Statsd.increment("flume.#{hostname}.#{name}.channel_size", channel.size) # from wherever hostname and name come…
end

puts "#{status.upcase} - #{relevant_channels.join(";")}"
exit exit_code