Consul watch script for updating a Linode NodeBalancer's config

balance.rb

#!/usr/bin/env ruby
#
# This script is intended to be run as part of a Consul watch listening for services.
# It then uses Linode's API to remove nodes no longer available, and to add new ones.
#

require 'json'
require 'httparty'

BALANCER_NAME, CONFIG_PORT = ARGV
API_KEY = '...'
HEADERS = {"Authorization" => "Bearer #{API_KEY}"}

resp = HTTParty.get("https://api.linode.com/v4/nodebalancers", :headers => {"Authorization" => "Bearer #{API_KEY}"})
balancer = resp["data"].find do |node|
  node["label"] == BALANCER_NAME
end

resp = HTTParty.get("https://api.linode.com/v4/nodebalancers/#{balancer["id"]}/configs", :headers => {"Authorization" => "Bearer #{API_KEY}"})
config = resp["data"].find do |node|
  node["port"] == CONFIG_PORT.to_i
end

id_map = {}
resp = HTTParty.get("https://api.linode.com/v4/nodebalancers/#{balancer["id"]}/configs/#{config["id"]}/nodes", :headers => {"Authorization" => "Bearer #{API_KEY}"})
have = resp["data"].map do |node|
  id_map[node["address"]] = node["id"]
  node["address"]
end

want = JSON.load(STDIN).map do |service|
  "#{service["Node"]["Address"]}:#{service["Service"]["Port"]}"
end

# remove old servers
(have - want).each do |addr|
  puts "[-] #{addr}"
  resp = HTTParty.delete("https://api.linode.com/v4/nodebalancers/#{balancer["id"]}/configs/#{config["id"]}/nodes/#{id_map[addr]}", :headers => {"Authorization" => "Bearer #{API_KEY}"})
  if resp["errors"]
    puts "  errors found: #{resp["errors"]}"
  end
end

# add new servers
(want - have).each do |addr|
  puts "[+] #{addr}"
  resp = HTTParty.post("https://api.linode.com/v4/nodebalancers/#{balancer["id"]}/configs/#{config["id"]}/nodes", :headers => {"Authorization" => "Bearer #{API_KEY}", "Content-Type" => "application/json"}, :body => {
    :address => addr,
    :label => `uuidgen`.strip.gsub('-', ''),
  }.to_json)
  if resp["errors"]
    puts "  errors found: #{response["errors"]}"
  end
end